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AT1000 User Manual - Amplitrex Audio Products

1. T OPERATION SWITCH OFF THE POWER BEFORE INSERTING OR REMOVING A RECTIFIER TUBE SOCKET H WARNING MOST VACUUM T ACCIDENTALLY BROKEN GL OR OTHER INJURY JEAN OVES BE AWARE THAT S ALS IN THIS CASE C R INFORMATION CAREF SPOSE OF IN TRASH D ONTAINING MERCURY S C S RE CONSTRUCTED WITH GLASS ENVELOPES IF ENTS WILL BE SHARP AND CAN CAUSE CUTS OKEN TUBE PARTS CAREFULLY USING PROTECTIVE BES MAY CONTAIN SMALL AMOUNTS OF HAZARDOUS E TUBE MANUFACTURER S MSDS FOR HEAVY PAPER FUMES A ER PRESENTS A IF oA Oo HQ F BE O i ULLY WRAP BROKEN TUBE FRA O NOT BREATHE ANY POSSIBLE UCH AS A MERCURY VAPOR RECT O H A TER RTH DD Q S OHUMDWO 2 H n H Z I EC TH HAZARD IF BROKEN URY CONTAINING TUB SELF WITHOUT THE P F T U TACT LOCAL EMERGENCY AUTH w Za Q E PY gt Z S E ROKEN DO NOT ATTEMPT TO IT UP ROPER EQUIPMENT PERSONAL PROETCTIVE GEAR AND ER FROM THE UNIT AND MOVE TO FRESH AIR RY CONTAINING TUBE IS BROKEN R TO A BHG ZG O GW wW EXE DURES DISCONNEC EDIATELY IS A ME
2. 4 When ready the user presses ENTER The Transconductance Test starts and for a few seconds the statement Please Wait is displayed Following this another prompt to press ENTER when ready is shown This allows the user to wait again for an unstable or drifting reading to stabilize before continuing As before the unit will wait indefinitely for the user to press the ENTER key to continue The Audio output is muted during the Transconductance test CAUTION PROLONGED RUNNING OF A POWER TUBE MAY CAUSE THE UNIT TO OVERHEAT AND SHUT DOWN 5 The Gas Test runs Audio output continues to be muted 6 B is switched off and the Results Screen is displayed In the Manual Test Mode the plate current value is recorded just as the user presses ENTER to move to the Transconductance Test In a similar way the average Transconductance value is recorded just when the user presses ENTER to continue to the Gas Test The most recent complete set of 10 measurements over an 8 second interval is then used to determine the average transconductance value 10 6 OVERHEATING DURING CONTINUOUS MANUAL MODE The AT1000 has a finite heatsink and ventilation fan which serves to cool the plate and screen regulators For tubes under about 50 mA of plate current virtually continuous running can be expected without overheating
3. Blown fuse inside the unit Contact the factory for instructions 5 5 Plate Current iP increases during the Transconductance Test This is normal Firmware Version 2 08 and later displays updated Plate and Screen Current while Transconductance is being measured The increase in Plate Current is due to the fact that the tube is amplifying a 1kHz signal The Plate Current is measured for the Results Screen before the 1 kHz signal is applied so that an accurate Measured Plate Current reading is obtained 5 6 Unable to upload a new Tube Test Data File Make sure that you have configured the Tubedata Editor Software for the COM port that you are using Make sure you are using a known good pin for pin wired serial cable Make sure that the AT1000 is in the Upload Mode see Section 7 of this manual Make sure that the data file is in the correct directory and that it is not corrupt You can view a CSV file using Notepad 5 7 Unit overheats frequently Make sure that the ventilation openings are not obstructed by objects or dust Clean if necessary Make sure that the fan is running when power is applied and the unit is switched on Continuous re testing or using in Manual Test Mode for too long with a high power tube may eventually cause the unit to overheat Allow more time between tests or operate at a lower plate current for burn in testing If the problem persists contact the factory 6 0 EDITIN
4. After configuring a test for an Electron Ray Indicator Display Section test it and observe the results You may find that a slight adjustment of the Ray Control Maximum Voltage produces a better display When setting up to test the triode section of an electron ray indicator set things up like you would for a normal triode Leave the Target Electrode Pin unconnected If the Ray Control Electrode is connected internally to the triode plate use this pin as the triode plate If the Ray Control Electrode and the triode plate are brought out on separate pins leave the Ray Control Electrode Pin unconnected The transconductance for the triode section of Electron Ray Tubes is rarely mentioned in the data sheet Normally these triodes have very low transconductance and any transconductance at all probably indicates a triode with satisfactory performance More important is the ability to establish the Operating Point at an acceptable minimum grid voltage This indicates sufficient emission and function can be assumed to be normal Use the value of plate voltage and the series resistor recommendations from the tube s data sheet to determine what plate current to use for the Operating Point Assume that half of the supply voltage is being dropped across the resistor and then figure the plate current Use this value for the Plate Current in the triode section test Successfully adding an electron ray indicator tube ma
5. The rectifier test does not shut down if there is a short however the forward and reverse voltage drops will indicate the defect e If the unit s pass transistor heatsink overheats during operation a message to this effect will be displayed to the user Allow the unit to cool before attempting to resume operations Make sure that the fan is operating and that the ventilation openings are not obstructed Over heating will normally not occur except during prolonged continuous operation above 70 mA iP at plate voltages below 300V The rectifier test load resistors share the same heatsink so extended rectifier testing may also cause overheating 3 2 NOISE AND MICROPHONICS TEST E During the part of the tube test where B is applied and plate current is flowing but the transconductance test has not yet started you can listen to tube noise You must select the Continuous Manual Test Mode see section 8 0 so that the Headphone Amplifier is enabled Connect a 4 to 32 ohm stereo headphone not included to the 1 4 Audio Out connector on the panel Use the Volume Control on the left side of the panel to control the volume The audio is muted during the B ramp up and plate current stabilization periods and when the Transconductance and Gas Tests are running The Noise and Microphonics Test is useful for identifying preamplifier tubes that are microphonic Tap gently on the tube envelope with a pencil or small s
6. when the number 1 appears in the Tube Type Code field a Tetrode or Pentode tube will be tested in Triode mode In this case the screen grid pin number must be specified in field 12 so that the AT1000 can connect it in parallel with the plate Two other characters may be entered in the first three of these four pin designation Fields They are and If the Grid 1 electrode is connected to a cap on top of the tube enter the asterisk in the Grid Pin Field If the Plate is connected to a cap on the tube enter the number symbol in the Plate Pin Field The last one of these four Pin Identification Fields 14 contains a three digit sequence This field MUST always contain three digits These three digits specify individually any pins on the tube that should be connected to Ground Normally the cathode of a tube is connected to ground so the cathode pin number is frequently the first digit of the three digit sequence In the case of a Pentode tube sometimes the Suppressor Grid is brought out to a separate pin instead of being internally connected to the cathode A good example is the 6CA7 EL34 pentode In this case make the pin number that the suppressor grid is connected to the second digit of this three digit sequence If there is any other pin that should be connected to ground place that pin number in the third digit position One example is the octal metal shell tubes Usually Pin 1 is connected to the metal shell c
7. about 70 can be classified as bad However you must be the one to determine for yourself if a tube with 70 emission or GM is suitable for use or not For example a tube showing 70 may perform very poorly in one piece of equipment yet be OK in another The third item displayed on the fourth line is the result of the Gas Test During the Gas Test the grid circuit source impedance is increased 10 times Plate current is measured before and then again after the impedance is altered If there is residual gas inside the tube the ion current flowing in the gas between the plate or screen and the grid causes the grid to become more positive less negative This produces an increase in plate current this difference is the value that is displayed in milliamperes When interpreting Gas Test results one must take into consideration several things First the normal plate current Second what is the application of the tube And third how much gas induced current increase was measured In the case of a small preamp tube like a 12AX7 or EF86 anything more than 0 1 milliampere of gas current will likely cause problems in the application circuit Noise may be excessive and or the tube may not establish its correct operating point With a power tube like a 6L6 the interpretation must be different Power tubes typically show a few milliamperes of gas induced current increase even if they are good This is because in
8. these tubes plate temperatures are generally much higher and there is more surface area on the plate and other tube components which naturally outgass somewhat as it heats up Also because these tubes normally operate with several tens of milliamperes or even over 100 milliamperes a few mA of Gas current is OK With power tubes a gas induced current increase of less than 10 percent of normal plate current is OK in most application circuits When performing repeated tests hot retest on a power tube the re application of plate current to an already hot tube sometimes causes even MORE gas induced current to be measured the second time If the amount of current increase is more than about 10 percent of the tubes normal plate current it is likely to produce noise in the circuit as well as a possible run away condition Whether or not this will happen depends on factors such as grid circuit impedance in the target application and the values of plate voltage and current the tube is being run at Occasionally a run away condition will result while the tube is in the AT1000 and this will cause an overcurrent shutdown and the message possible excessive gas to be displayed 4 2 DIODE RESULTS SCREEN In the case of tubes that contain diodes or diode sections such as the 6AL5 and 6T8 the Diode Results screen will be displayed In addition to the Heater to Cathode Leakage measurement that appears o
9. 6 3 HEATER CATHODE CODES Indirectly Heated Heater Cathode Tubes e g 6L6 12AX7 cov OV OV 3V saV 12 6V 1 0V 1 5V 2 0V 7 5V 10 0V 4 0V ll UNDOWDY ROH ODAUOWD ll Directly Heated Filament Type Tubes e g 2A3 305 5V OV OV 3V saN 126V 1 0V 1 5V 2 0V Te DV 10 0V 4 0V ll ll UNO WDY MSSCCQCHNDWOUVUOZE II T oD 5 PLATE VOLTAG Eal The next Field 5 contains a three digit numerical entry that specifies the Plate Voltage for the test Valid voltages are between 45 and 500 Note that when the voltage is below 100 you must insert a leading zero e g 090 for 90 volts Only whole numbers may be used giving one volt resolution Entries outside the range of 45 to 500 volts should not be used If this is done the voltage applied to the tube is unpredictable Settings below 45 volts may produce the correct voltage but the Plate Current measuring circuit may not give an accurate reading 6 6 SCREEN VOLTAG T ea The next Field 6 contains another three digit numerical entry that specifies the Screen Grid 2 voltage for the tube Valid voltages are between 45 and 500 same as the Plate The Screen voltage may be set to something less than or equal to the plate voltage The Screen voltage must NOT be set higher than the Plate as unpredictable operation and or tube damage may result Entries outside th
10. A TUBE S PINS INTO THE TUBE SOCKETS ON THI Gl CONTACT WITH HIGH VOLTAGE CAN CAUSE SERIOUS INJURY CARDIAC ARREST OR DEATH T WARNING THE AT1000 MUST BE CONNECTED ONLY TO AN AC POWER OUTLET THAT IS PROPERLY GROUNDED DO NOT ATTEMPT TO DEFEAT THE GROUND CONNECTION BY USING ADAPTERS OR BY REMOVING THE GROUND PIN S FROM THE POWER CORD OR INLET ELECTRICAL SHOCK ELECTROCUTION OR FIRE MAY RESULT TJ REPLACE THE POWER CORD IF IT BECOMES DAMAGED IN ANY WAY 7j WARNING KEEP THIS UNIT OUT OF THE REACH OF CHILDREN OPERATION BY NON TECHNICAL RSONNEL MUST BE SUPERVISED CLOSELY BY A PERSON FAMILLIAR R U T WITH THESE OPERATING INSTRUCTIONS ESPECIALLY THESE WARNINGS AND WITH HIGH VOLTAGE SAFETY IN GENERAL DO NOT ALLOW CHILDREN TO OPERATE THIS EQUIPMENT WARNING VACUUM TUBES CAN BECOME EXTREMELY HOT DURING TESTI PLOTTING DO NOT HANDLE HOT TUBES WITH BARE HANDS ALLOW TUBES FOLLOWING OPERATIONS BEFORE REMOVING THEM FROM A TEST SOCKET U PROTECTIVE GLOVES IF IT IS NECESSARY TO HANDLE HOT TUBES NEVER REMOVE A TUBE WHILE POWER IS APPLIED TO IT UNDER TEST OR DURING A CURVE PLOTTING
11. AT1000 Vacuum Tube Tester Operations Manual Applies to firmware version 2 12 and later 22 July 2009 TABLE OF CONTENTS RECAUTIONS AND WARNINGS RONT PANEL COMPONENTS SIC OPERATION TERPRETING RESULTS ROUBLESHOOTING DITING TEST DATA AND ADDING TUB PLOADING THE TEST DATA FILE HE SYSTEM MENUS A USING THE CURVE PLOTTING SOFTWAR 0 0 BIASING AND TESTING MODES D Gl Z Gl wn HCQMHHWH U oo Oo 0 Oo Oo 0 OO Gl 1 0 PRECAUTIONS AND WARNINGS Gl WARNING THE AT1000 VACUUM TUBE T ERATES AND USES HIGH VOLTAGE FOLLOW ALL INSTRUCTIONS CAREFULLY NEVER TOUCH OR REMOVE A TUBE WHILE TESTING OR CURVE PLOTTING IS IN PROGRESS NEVER TOUCH ANY TUBE PINS SOCKET CONTACTS OR PLATE OR GRID CAP METAL PARTS WHILE THE UNIT IS CONNECTED TO A SOURCE OF AC POWER UNPLUG THE UNIT WHEN NOT IN USE T IF A TUBE SOCKET IS BROKEN THE METAL CONTACTS INSIDE IT MAY BECOME EXPOSED IF THIS OCCURS STOP USING THE UNIT AND HAVE IT REPAIRED BEFORE USING IT AGAIN Gl T DO NOT USE THE UNIT WITH WET OR PRESPIRING HANDS MOISTURE INCREASES THE RISK OF SHOCK AND ELECTROCUTION NEVER INSERT ANYTHING EXC AT1000 z PT
12. DATA FILE To upload a new or modified Data File to the AT1000 proceed as follows a Check to make sure that any editing done has not changed the total NUMBER of characters in Fields 2 through 15 in each Record Make sure no extra or missing commas are present as well b You may rename the new file anything you want but keep the CSV filename extension If you will use the new TubeData file with the TubeTest software you must name the file tubedata csv with no version number as the software looks for that file name only TubeData Editor which is used to upload the file directly to the AT1000 can use any filename that ends with CSV c Follow the directions for the software program TubeData Editor to upload the file to the AT1000 and store it in its non volatile memory 8 0 THE SYSTEM MENUS The AT1000 provides several different System Menus These menus are used to select various operating options for the unit Some of the settings that you can change are stored in non volatile EEPROM memory so that the settings are remembered when the unit is disconnected from a source of power 8 1 ENTERING THE TOP SYSTEM MENU zr To enter the first top System Menu proceed as follows 1 Switch OFF the AT1000 Wait at least 10 seconds 2 Hold down the left arrow lt key and while holding it switch the power switch ON Continue to press the lef
13. Even with these adjustments closely matching the emission of each tube greatly improves performance and long term reliability To match tubes by transconductance first make sure that the emission is within 10 for the tubes Then compare transconductance readings between tubes for a 5 or better match For preamplifier tubes emission and transconductance matching can also improve performance Particularly in long tail pair phase splitter operation the tubes or tube sections should be closely matched If the phase splitter is operating as symmetrically as possible distortion will be reduced and drive to the output stage will increase Sometimes there are driver tubes after the phase splitter but before the output tubes These tubes should also be matched so that drive to the outputs remains as symmetrical as possible throughout the signal path Fully differential preamplifiers often used in the recording industry will be push pull from input to output transformers Keeping things balanced throughout the signal path is essential to take advantage of the wide bandwidth low noise and low distortion this equipment is capable of 4 6 WARMUP AND OTHER FORMS OF DRIFT In electronics even vacuum tube electronics it is nice to keep things consistent and under control With well designed circuits running the tubes well within maximum ratings one can expect stable operation Occasionally tubes will exhibit var
14. G TEST DATA AND ADDING TUBES The AT1000 is shipped along with a CD ROM which contains several files One of these files is TUBEDATAxxx CSV This file contains all of the test setup data which the AT1000 uses for testing tubes xxx represents the Version Number of the TubeData File TUBEDATAxxx CSV is a Comma Delimited File We recommend that you open and edit the file with using Notepad You can also edit the file using TubeData Editor See the separate instructions if you intend to edit the file using this program If editing it with Notepad make sure to save the file as plain text with the CSV filename extension The user is advised to save a copy of the TUBEDATAxx CSV file ina safe place This way in case the working copy is damaged lost or becomes corrupted you can retrieve the original file s Editing the file is easy When using Notepad you will see a series of lines of text Each line is called a Record and is comprised of exactly 15 data Fields each separated by a comma Each Record contains the test data for one tube or in the case of multi section tubes the test data for one section Note that some of the data in some of the fields contain leading zeros It is EXTREMELY IMPORTANT that the correct number of characters are present in each Field of each Record The only Field that can have a variable number of characters in it is the first one in each Record which is the Tu
15. However when a high power tube is left to run for 2 minutes or more the heatsink may overheat and the unit will shut down No damage will be done as the unit is designed to sense excessive heat and end the test should it occur If an Overheat Condition is displayed allow several minutes for the regulators to cool with the Power Switch left ON so the fan runs before continuing with testing Also be aware of so called run away tubes when using Continuous Manual Mode If a power tube tends to show rapid ever increasing plate current iP you may have a run away tube You should manually end the test by pressing the Left Arrow lt Key if this condition occurs and dispose of the tube as faulty 2004 2009 Amplitrex Audio Products
16. IFIER WIRED TO PINS 2 AND 4 NEVER THE UNIT IS SWITCHED ON EVEN IF A TEST IS NOT IN PROGRESS IT IS RECOMMENDED THAT THE UNIT BE SWITCHED OFF BEFORE RECTIFIER TUBES ARE INSERTED OR REMOVED FROM SOCKET H THIS WILL MINIMIZE THE POSSIBILITY OF CONTACT WITH DANGEROUS VOLTAGE SHOULD THE TUBE BREAK WHILE INSERTING REMOVING OR IF UBE TEST SOCKET SOCKET H HIS VOLTAGE IS PRESENT WHI HAS HIGH VOLTAGE AC T T ar es Gl C7 FINGERS COME INTO CONTACT WITH LIVE PINS CAUTION INCORRECT TEST SETUP OR INCORRECT SELECTION OF TUBE TYPE OR TEST SOCKET CAN DAMAGE THE TESTER AND DAMAGE OR DESTROY A TUBE AMPLITREX AUDIO PRODUCTS ACCEPTS NO RESPONSIBILITY FOR TUBES WHICH MAY BE DAMAGED DURING TESTING 2 0 FRONT PANEL COMPONENTS TUBE SOCKETS The unit is equipped with 8 high quality tube sockets Each socket is identified with a letter of the alphabet A through H During test setup the LCD screen tells the user which socket to use Some users may elect to use socket savers to prolong the life of the sockets in the AT1000 This is an especially important consideration if large numbers of tubes are to be tested such as in a manufacturing or large batch matching
17. N EXPOSED TO MOISTURE IF THE UNIT HAS SUFFERED DAMAGE IN SHIPPING OTHERWISE OBVIOUSLY DAMAGED DO NOT CONNECT RETURN IT TO THE FACTORY FOR INSPECTION AND HAS BEEN DROPPED OR IT TO A SOURCE OF AC POW REPAIR E E ve Gl WARNING DO NOT OBSTRUCT VENTILLATION OPENINGS ENSURE THAT THE COOLING FAN IS OPERATING AND VENTILLATION OPENINGS ARE UNOBSTRUCTED BEFORE NNING OPERATIONS DO NOT ALLOW ANY FORIEGN SUBSTANCE OR OBJECT TO ER ANY OPENINGS CONTACT WITH HIGH VOLTAGE MAY RESULT CAUSING DAMAGI F U T i td Gl ESTRUCTION OF PROPERTY AND POSSIBLE INJURY OR DEATH DUE TO FIRE OR ROCUTION El T ARNING DO NOT INSERT A TUBE UNTIL THE TEST HAS BEEN SET UP EXCEPTION ERS AND THEN ONLY INSERT THE TUBE INTO THE CORRECT SOCKET DO ERT MORE THAN ONE TUBE AT A TIMI DAMAGE THE AT1000 OR THE F E E R V W Gl UBE S MAY RESULT DO NOT ATTEMPT TO TEST A BROKEN TUBI ONE WHERE HE GETTER FLASH NORMALLY SILVER IN COLOR HAS TURNED HHZ WS O E H H A n El El T 4 WARNING THE RECT
18. RC HUK ES DH Pp 5 IF A TUBE GLASS ENVE DISCONNECT THE UNIT F T REAKS WHILE IT IS PLUGGED INTO THE AT1000 TS SOURCE OF AC POWER AS SOON AS POSSIBLE WAIT AT LEAST 2 MINU R ALL HIGH VOLTAGE TO BE DISCHARGED AUTOMATICALLY BY BLEEDER RESISTORS IN THE UNIT BEFORE ATTEMPTING TO REMOVE THE REMAINS BE CAREFUL OF SHARP GLASS AND HOT FRAGMENTS PLIERS MAY BE USEFUL IN REMOVING BROKEN TUBE BASE FRAGMENTS IN THE CASE OF MINIATURE TUBES How O Ov S Jj N raj O EJ T WARNING THE AT1000 CONTAINS FUSES AND A THERMAL PROTECTIVE DEVICE DO NOT REPLACE WITH OTHER THAN IDENTICAL COMPONENTS OR BYPASS THESE SAFETY DEVICES DOING SO WILL VOID YOUR WARRANTY AND MAY RESULT IN FIRE DAMAGI O OR LOSS OF PROPERTY AND PERSONAL INJURY OR DEATH DO NOT ATTEMPT PAIR OF THE UNIT YOURSELF RETURN A DEFECTIVE UNIT TO THE FACTORY FOR PAIRS e ti T R R BL EI WARNING DO NOT EXPOSE THE UNIT TO MOISTURE RAIN OR OTHER LIQUIDS DOING SO VOIDS YOUR WARRANTY AND MAKES THE UNIT UNSAFE TO OPERATE UNTIL REPAIRED BY THE FACTORY FIRE PROPERTY DAMAGE AND PERSONAL INJURY OR DEATH MAY RESULT FROM THE OPERATION OF A UNIT THAT HAS BEE
19. after Bt is applied to the tube but before the Transconductance Test is run In Auto Bias Mode the microcontroller inside the AT1000 adjusts the grid bias voltage so that the specified plate current is achieved in the tube Then it will continue to test Transconductance When the unit is set to Fixed Bias Mode however it operates differently B is applied to the tube and then a fixed bias voltage is applied to the grid This fixed voltage is obtained from the stored tube test settings or in the case of remote controlled testing it is obtained from settings in the TubeTest software In Auto Bias Mode the bias voltage is adjusted within limits to achieve rated plate current If the emission in the tube is less than normal for the type of tube the grid voltage may end up being somewhat lower than the specification Gl voltage However the plate current will be close to specification and the Transconductance Test is more likely under these circumstances to produce a near normal reading If the emission is very low in a tube tested under Auto Bias the bias voltage might be reduced to zero and rated plate current may never achieved In Fixed Bias Mode the bias voltage is set to the specification value Plate current will be whatever the tube is capable of at this fixed grid voltage With a weak tube tested under Fixed Bias Mode the plate current will likely be less than the specified plate current This will oft
20. as When the desired selection is displayed press ENTER to select it The unit then returns to the top System Menu 8 5 UPLOAD NEW TUBE DATA When Upload New Tube Data is displayed and then ENTER is pressed the unit prepares for the upload of a new tube data file Refer to Section 7 0 for further information T 8 6 FIRMWARE UPGRADE When Firmware Upgrade BootLoader is displayed pressing ENTER causes the unit to enter the Firmware Upgrade Mode See the separate instructions on the BootLoader for information on how to use it ea 8 7 CHANGI TEST DURATION When Change Test Duration is displayed and the ENTER key is pressed a sub menu is displayed Using the scroll keys lt and gt make a selection of either Timed automatic or Continuous manual When the desired selection is displayed press ENTER to select it The unit then returns to the top System Menu 8 8 CALIBRAT Ea RECTIFIER TEST This System Sub Menu is intended for Amplitrex service personnel only Contact us if you have questions about the Rectifier Test Calibration 8 9 RETURN TO TUBE TESTING When Return to Tube Testing is displayed pressing ENTER causes the unit to return to stand alone tube testing operation This is normally the way that the System Menus are exited after changing ei
21. be Type Number The format for each Record is as follows There are 15 Fields in each Record The first Field is for the tube type number and can contain a variable number of characters All of the remaining fields however MUST contain a total of 29 characters excluding the commas If there is an incorrect number of characters in a data record or if there are missing or extra commas the AT1000 will not be able to properly locate the test setup information This will lead to all kinds of problems such as incorrect voltage and pinout settings and failure of a test sequence to terminate properly The Fields are numbered left to right from 1 to 15 6 1 TUBE TYPE NUMBER The first Field contains the tube type number as mentioned above The characters are simply normal alphanumeric characters that you type on the keyboard For the tube type field it is recommended that you use only upper case characters and numbers and that you limit the length to no more than six characters Otherwise each line of the LCD display showing the list of tube numbers can become too long causing wrap around problems Tubes that use a Socket Adapter for testing have an asterisk appended to the tube type number In AT1000 units with firmware Version 2 08 and later the asterisk in the tube type number produces a prompt on the LCD screen that an Adapter is required 6 2 TUBE TYPE CODE The next Field 2 c
22. crewdriver handle and listen for any excessive ringing noise A slight noise when tapping on the tube is normal Higher gain tubes will usually exhibit greater microphonic noise You can listen to power tubes as well but use caution They will make very loud noises when struck gently due to their much larger physical structures They also get hot quickly Turn the volume up carefully from zero fully counter clockwise to avoid hearing damage The microphonic effects encountered with power tubes are generally of little concern as they are normally used in the final and lowest overall gain stages of amplifiers Nevertheless you may want to choose tubes with the lowest levels of microphonics Some background noise and hum will be heard as well Some of the noise comes from the tube and some from the AT1000 This is due to the unshielded nature of the internal tube socket wiring 3 3 USING A SPEAKER INSTEAD OF HEADPHONES You can connect a 4 to 16 ohm speaker to the Audio Out connector using a standard 1 4 stereo phone plug and some wire Connect the two hot terminals tip and ring of the plug together and to one lead of the speaker Connect the other speaker lead to the Common sleeve terminal on the plug Make sure that the hot terminals and the Common terminal do not touch when re assembling the plug and shell You can also connect an oscilloscope or AC voltmeter instead of a speaker by usi
23. d as to which socket on the AT1000 to insert the tube into Carefully insert the tube into the indicated socket and press ENTER again If the tube you are testing requires a Socket Adapter a screen will appear telling you that an Adapter is required and which Socket on the AT1000 you should connect the Adapter to Tubes in the Tube List with an Asterisk require the use of a Socket Adapter Refer to the specific Adapter Instruction Sheet for further information If the tube you are testing has a plate or grid cap another screen will appear advising which banana jack plate or grid to plug the cap lead into If this is the case connect the cap lead and then press ENTER It is not possible to test a tube that has two caps 5 At this point the test will begin automatically The heater will be ramped up to its specified voltage and a timer will count down When the counter reaches zero the Warmup phase ends the Heater to Cathode Leakage Test is done and then B is applied to the tube 6 B comes on and this is indicated on the LCD screen The tube is biased into conduction in one of two modes In Auto Bias Mode the grid voltage is adjusted downward automatically until the specification plate current is achieved In Fixed Bias Mode the specification bias voltage is applied to the grid and the plate current will be whatever results at this bias setting The user can change the Bias Mode by
24. e used again shortly RS232 SERIAL CONNECTOR This standard 9 pin D connector links the AT1000 to a personal computer serial port Use the provided standard male to female cable wired pin for pin for this connection Connect this cable whenever uploading a new Test Data File or performing curve plotting and tube testing with a personal computer It is also possible with firmware after V1 20 to update the firmware over the serial port The cable and a computer is not needed for tube testing in the Stand Alone Mode PLATE AND GRID CAP BANANNA JACKS These jacks are for use when testing tubes that have a plate or grid cap on them Use the appropriate supplied cap lead each accommodates a different cap size when testing tubes with caps Connect the lead to the appropriate jack plate or grid as instructed by the LCD screen Never touch the metal parts of the plate cap or the banana plug or jack Handle them only by touching the insulated plastic and ceramic parts Never connect or disconnect them while a test is in progress only when instructed to by the LCD display or when the Test Menu has been exited heater turns off AUDIO OUT CONNECTOR AND VOLUME CONTROL The Audio Out connector is a standard 1 4 Stereo jack You can connect headphones or a speaker or an oscilloscope or AC voltmeter here The Volume Control a small knob located on the left side of the panel controls the level of signals pre
25. e heater 5 pin small base pins 1 and 5 are heater 6 pin small base pins 1 and 6 are heater Octal socket pins 2 and 7 are heater Octal socket pins 7 and 8 are heater 9 pin miniature socket pins 4 and 5 are heater 7 pin miniature socket pins 3 and 4 are heater Octal socket for 5 volt Rectifier tubes such as 5U4 and GZ34 Toa EO AWP Note that for each socket A through G the pins designated as heater or filament are hard wired and are not configurable All the other pins on each socket are connected to a switch matrix under control of the microprocessor and can be configured to the specific tube at run time Socket H is ONLY wired to test 5 volt heater filament tubes with JEDEC pin designations 5T or 5L Other rectifiers such as the 6X4 6X5 6CA4 EZ81 and 12X4 can be tested with the optional Amplitrex Rectifier Test Adapter If you want to add a tube and its heater pins are not compatible with one of the configurations listed above you must use a Socket Adapter Socket Adapters can be obtained from Amplitrex for several tubes that cannot be tested directly in one of the built in Sockets 6 4 HEATER CODE The next Field 4 contains a single upper case letter which denotes the heater or filament voltage It also denotes whether or not a tube has a directly heated filament or an indirectly heated cathode The table below shows a list of the Heater Cathode Codes TABLE
26. e range of 45 to 500 volts should not be used If this is done the voltage applied to the tube is unpredictable Settings below 45 volts may produce the correct voltage but the Screen Current measuring circuit may not give an accurate reading Like the Plate Voltage field Screen voltages less than 100 must contain a leading zero and only whole numbers may be used This gives the same resolution as for the Plate Voltage 1 volt In the case of a triode or a Tetrode or Pentode being tested in Triode Mode enter the numbers 000 in this field This sets the Screen Grid Power Supply fully OFF during the test 6 7 PLATE CURRENT The next Field 7 contains a four digit entry that specifies the Operating Point Plate Current The valid range is from zero 0000 to 160 0 1600 milliamperes Note that the four digits correspond to three Significant digits and one decimal place when the AT1000 runs a test The Plate Current resolution is 0 1 mA For example to set plate current to 1 2 mA enter the numbers 0012 To set plate current to 123 5 mA enter 1235 This entry MUST contain four digits and must have leading zeros if necessary Do not use a decimal point Do not attempt to set the Plate Current higher than 160 0 mA Damage to the tube or to the tube tester may result 6 8 SCRI 7 NT EN CURRI E The next Field 8 contains a three digit entry that specifies the expected Screen Grid 2 Curre
27. e voltage during the test for both sections The results for both sections are shown on the same screen and there is no need to move between sections with the up and down arrow key During the rectifier test a sinusoidal voltage of 275V RMS nominal is applied 180 degrees out of phase on each plate This is how these tubes are generally run in an application circuit Series load resistors are provided in each plate s circuit and the voltage drop between each plate and the cathode is measured In case a tube is shorted the load resistors prevent damage to the tester by harmlessly dissipating the reverse conducted current Normally rectifier tubes will read between 10 and 70 volts forward drop depending on the rating of the tube Mercury rectifiers read the lowest and small high vacuum types such as the 5Y3 read the highest The appropriate tube data sheet should be consulted to determine the expected forward drop at a peak current of about 100 mA The reverse voltage drop should be much higher typically between 390 and 405 volts peak The actual reading will vary with local mains voltage and the amount of mains waveform distortion that is present 4 5 MATCHING TUBI Gl S Vacuum tubes can be matched for use in balanced circuits such as push pull output or fully differential preamplifier use Single section tubes can be matched to each other and dual section tubes can have their sections matched as well as e
28. ed In Fixed Bias Mode if actual plate current is greater than specification this also indicates the tube has strong emission And if actual plate current is very low or zero the tube is bad and should be replaced Some tubes of modern manufacture may show lower than normal grid voltage in Auto Bias Mode or lower than normal plate current in Fixed Bias Mode as some new tubes are not being manufactured to the same standards as they were in the vintage years The actual measured transconductance is shown on the right side of the third line of the display This value is determined by actually making the tube amplify a 1 kHz sine wave signal and then measuring the AC plate current that results A reading of one milliampere per volt means that with a one volt RMS AC grid Signal a one milliampere RMS AC current was observed in the tube Transconductance normally reads close to the specification value If transconductance reads low this means that tube gain may be less than that expected in its application circuit If it reads higher than the specification more gain can be expected in the target circuit If emission was low low measured grid voltage or low measured plate current the transconductance can be expected to possibly but not always be low as well Note that the transconductance and emission values obtained with the triode DC amplifier section of an electron ray tube may read very low This does not necessaril
29. en also be accompanied by a reduced transconductance measurement 10 2 WHICH BIASING MODE TO USE Fa This is often a preference of the user Many application circuits operate using what is often called self bias cathode bias or auto bias In such a circuit there is a resistance in series between the cathode and ground and also a resistance that holds the grid at a fixed usually ground potential In such a circuit the tube bias is somewhat self adjusting because as the plate current changes it causes a change in the voltage drop across the cathode resistor This voltage drop subsequently forms all or at least part of the grid voltage A self controlling feedback loop is thus formed and the tube will tend to adjust its grid voltage and subsequently its plate current should the tube emission begin to drift Other applications usually the power output stage of an audio amplifier will use fixed bias Often there is a potentiometer available to actually change this fixed bias Nevertheless it is still called fixed bias In such a circuit drift or aging of the tube will not be compensated for and the tube s performance will vary The two Bias Modes are available so as allow test conditions that closely replicate actual tube operating conditions Most vintage tube testers operate using fixed bias If you are trying to compare test results between the AT1000 and other testers you sho
30. ght notice that all the Fields except the Pin Identification and the Section Identification Fields are identical 6 13 THE DIODI EJ TEST Examine one of the two Records in the Test Data File for the dual diode tube 6AL5 After the initial four Fields specifying tube number type heater and socket note that all of the plate screen and control grid voltage and current fields are all filled with zeros Same goes for the transconductance field Following that you will see that the only Pin Identification Fields that do not have zeros are the plate and cathode pins for that section The Screen and Grid 1 Fields have zeros also This is the correct way to configure a diode tube section for testing Simply use the 6AL5 as a template and change the plate and cathode pins to suit your tube 6 14 THE ELECTRON RAY INDICATOR TI EJ ST Refer to the test Records for the 6E5 tube Note that there are two sections in this tube the display section and the triode DC amplifier The first section tested is the display section and it has a type code of U When setting up to test an electron ray tube s display section pay particular attention to the fields as some of them have a re assigned meaning The Plate Voltage Field becomes the Target Voltage Field Use the recommended typical target voltage in the tube data sheet for this parameter The Screen Voltage Field becomes the Shadow Co
31. h 10 measurements of transconductance are performed and averaged for the final result 4 The Gas Test runs 5 B is switched off and the Results Screen is displayed The Audio Output is muted throughout the test when using Timed Automatic Mode Switch to the Continuous Manual Mode when it is desired to use the Audio Output Gl 10 5 CONTINUOUS MANUAL TEST MOD In Continuous Manual Mode the user is involved in the test process by watching the tests proceed and manually deciding when to advance to the next test using the ENTER key In Manual Mode the unit does the following after a tube is inserted into the socket and ENTER is initially pressed 1 The Heater is warmed up in the same manner as for Timed Automatic Mode 2 B is applied and then either Fixed or Auto Bias is used to obtain current flow in the tube 3 The unit prompts the user to press ENTER when ready As long as the user does not press ENTER plate current and screen current in a tetrode or pentode is actively measured and displayed This continues indefinitely until ENTER is pressed This allows the user to wait for plate current to stabilize before continuing You can also use this time to listen to tube noise and microphonics by using the Audio Out connector CAUTION PROLONGED OPERATION OF A POWER TUBE MAY CAUSE THE UNIT TO OVERHEAT AND SHUT DOWN
32. heck the data sheet for the tube So a 1 should be placed in one of these three digit positions to ensure that the metal envelope is grounded Make sure to do this with tubes that come in either glass OR metal envelopes like the 6L6 and the 12SQ7 WARNING NEVER ACCIDENTALLY ASSIGN A METAL SHELL TUBE S GROUND PIN TO ANYTHING EXCEPT GROUND DOING SO CREATES AN EXTREME SHOCK AND ELECTROCUTION HAZARD WHEN WORKING WITH METAL TUBES ADDING TO OR T G ALTERING AN EXISTING TEST ALWAYS DOUBLE CHECK THAT THE METAL SHELL CONNECTION PIN IS SPECIFIED TO BE CONNECTED TO GROUND ONLY In the case of a Directly Heated tube such as the 300B DO NOT connect one of the filament pins 1 and 4 on the 300B to ground The AT1000 automatically grounds one side of the filament when testing directly heated filament tubes It knows whether or not the tube is a directly heated type from the code you entered in Section 6 4 above If no pins need to be connected to ground such as with the 300B enter 000 in this field Remember there must ALWAYS be THREE digits here If only the cathode needs to be connected to ground enter this pin number in the first digit and enter zeros for the remaining two digits 6 12 SECTION IDENTIFICATION FIELD The final Field 15 contains a single digi
33. ious types of drift The most common type of drift is caused by the heater cathode assembly in the tube It often gets worse as the tube ages Most often this form of drift takes place over several minutes or tens of minutes and starts out as low emission gradually rising as time passes At some point the upwards emission drift diminishes to zero and the tube becomes stable Generally it is desirable for power tubes to warm up fully in one to two minutes Smaller tubes can be expected to stabilize in as little as 30 seconds Directly heated tubes generally exhibit stable emission in only 15 to 30 seconds As a tube ages the cathode oxide coating used in most tubes becomes worn out It can also be damaged by heater undervoltage overvoltage or too much emission current Not to mention the effects of residual gas and air left in the tube The effect of this aging and damage is a slow to warmup tube These tubes also generally exhibit low ultimate emission and lower than normal transconductance Another form of drift manifests by physical distortion of tube electrodes and their spacing caused by heat or selective electron bombardment These causes can make emission and or transconductrance drift up OR down as the tube operates Sometimes the drift is random in either direction even after hours of warmup time After many years of operation some tubes end up with severely distorted electrodes which produce various nonlineari
34. n the top line a reading for forward and reverse current is shown Normally forward current should be in excess of 900 microamperes and reverse current should be zero The test current is limited to 1 mA and this reading may only be seen in a shorted diode where the forward and reverse currents are almost the same Also heater to cathode leakage in diode sections is usually very critical because the cathode is frequently a signal point in the application circuit Heater to cathode leakage in diode sections should always read zero a reading of a microampere or two or more is probably reason for the user to discard the tube as bad There is no gas test for diode sections If the tube contains a triode or pentode or tetrode section as well the gas test will run only on the non diode sections 4 3 ELECTRON RAY INDICATOR RESULTS SCREEN Electron Ray Indicator tubes such as the 6E5 and EM84 can be tested on the AT1000 In these cases a special test is run on the display section of the tube During the test the tube s fluorescent screen will light up and the shadow will be moved as the AT1000 varies the Ray Control Electrode voltage The user should observe the fluorescent screen on the tube under test and evaluate the brightness and shadow movement for normal appearance Note that there is sometimes significant shadow overlap as the AT1000 delivers full B to the ray control electr
35. ng a stereo phone plug wired as above 4 0 INTERPRETING RESULTS After each series of tests concludes B is switched off heater power is maintained and test results are displayed on the LCD display If a tube has more than one section such as the 12AX7 Dual Triode tests will be conducted on both sections of the tube In the case of a 6T8 tube there are four sections Each is tested individually and the results appear on a separate screen Use the UP and DOWN arrow keys to review the test results for each section of a multi section tube If there is only one section in the tube the UP and DOWN arrow keys will only show one results screen If while in Manual Test Mode and during the Transconductance Test the ENTER key is pressed before the Please wait message disappears the transconductance result displayed will be zero To prevent this during Manual Test Mode wait until the Please wait message is replaced with Press ENTER to continue 4 1 TYPES OF RESULTS DISPLAY SCREENS There are four different types of Results Screens The first one is displayed if the tube or tube section is a triode tetrode or pentode It shows the following data a Top Line Heater to Cathode Leakage This is shown in microamperes and is tested by applying 200V to the heater while the cathode is held at ground potential Current is limited to 1 mA Normally a good tube
36. nit will stay in the mode of measuring transconductance and displaying it until ENTER is pressed When the transconductance test ends the 1 kHz test signal is turned off 8 Next the Gas Test begins For the gas test two plate current measurements are made One is made a fraction of a second after the 1 kHz grid signal is removed Then the grid circuit resistance is increased 10X and a few seconds are allowed to elapse Finally the second plate current measurement is made which is frequently higher The difference in these two readings becomes the Gas Result Value and indicates the effect of the tube s gas contents or other source of leakage to the grid on its grid electrode The Gas Test always operates automatically there is no difference between Timed and Manual Test Modes 9 After the gas test concludes B is removed from the tube and the Test Results Screen is displayed If there is more than one section in the tube under test the other section s are tested before the results are shown Each section of a multiple section tube is tested as if it was a separate tube and the results are shown separately for each section If the unit is set to Manual Test Mode the ENTER key must again be pressed to move from the Bias Function to the GM test and again to move from the GM test to the Gas test This is repeated for each section of the tube as it is tested 10 Review the re
37. nt The valid range is from zero 000 to 20 0 200 milliamperes Note that the three digits correspond to two significant digits and one decimal place when the AT1000 runs a test The Screen Current resolution is 0 1 mA For example to set screen current to 10 5 mA enter the numbers 105 To set screen current to 0 3 mA enter 003 This entry must contain three digits and must have leading zeros if necessary Do not use a decimal point In the case of a triode or a Tetrode or Pentode being tested in Triode mode enter the numbers 000 in this field 6 9 GRID 1 VOLTAG Gl The next Field 9 contains a three digit entry that specifies the Operating Point Control Grid Grid 1 Voltage The valid range is from 0 1 001 to 99 9 999 volts Note that the three digits correspond to two significant digits and one decimal place when the AT1000 runs a CESES For example to set grid 1 voltage to 14 5 enter the numbers 145 To set it to 0 5 V enter 005 This entry must contain three digits and must have leading zeros if necessary Do not use a decimal point When the AT1000 performs a test this parameter is used for two things First when B initially comes on the grid voltage is set to 2 TIMES that of the entry up to 150 volts Then in Auto Bias Mode the unit sets the operating point beginning from there and decrements lowers the voltage In Fixed Bias Mode the Gl voltage is set to 2 times the entry value up t
38. ntrol Electrode Maximum Voltage Normally it should be set to the same value as the Target Voltage During test the AT1000 ramps the Ray Control electrode between zero and this voltage This will normally cause the Indicator Tube s shadow to traverse its entire range The Plate Current Field becomes the Target Current parameter Enter the expected peak target current here The Screen Current and the Transconductance fields are filled with zeros for the display section The Grid Voltage Field still functions as the Grid Voltage setting for the DC amplifier triode section during the Indicator Section Test Because the AT1000 will be driving the ray control electrode directly with its screen voltage supply it is desirable to bias the triode section completely off 30 or 40 volts is generally sufficient to accomplish this task When configuring the pins for the Display Section enter the Target Pin number in the Plate Pin Field Enter the Ray Control Electrode Pin number in the Screen Pin Field Enter the triode section s grid pin number in the Grid Pin Field Then enter the cathode pin as one of the ground pins in the Ground Pins Field If the tube has it s ray control electrode internally connected to the plate of its triode use this pin as the Ray Control Pin If the tube brings the Ray Control Electrode and the triode plate out on separate pins leave the triode plate unconnected for the Indicator Test
39. o 150 volts Then after B is applied the grid voltage is set to the value corresponding to the entry This ensures that a tube never has B initially applied with too little negative grid bias and therefore possibly too much plate current 6 10 TRANSCONDUCTANC Gl The next Field 10 contains a three digit entry that specifies the expected transconductance value The valid range is from 0 1 001 to 50 0 500 mA V Note that the three digits correspond to two Significant digits and one decimal place when the AT1000 runs a test For example to set up the test to expect 11 0 mA V 11 000 uMHOs enter the numbers 110 For 0 5 mA V 500 uMHOs set it to 005 This parameter is used only as the spec value for transconductance in the Results Screen The AT1000 automatically sets the transconductance preamp gain and calculates the actual transconductance during a test 6 11 TUBE PINS CONFIGURATION The next four Fields 11 12 13 and 14 contain numerical entries that specify the pin connections for the tube to be tested The first three Fields of these four specify which pin is connected to the Plate Screen and Grid 1 electrodes respectively Valid numbers are 0 zero through the highest pin number on the socket which was specified earlier An entry of 0 designates that there is no electrode of that type in the tube This is most commonly used with a triode tube which has no screen grid However
40. ode as would happen in normal operation of the DC amplifier triode section if so equipped when it was fully cut off Once the tests conclude the Results Screen for the Indicator Section will show the maximum achieved target current in the tube Target current varies as the shadow moves because more or less electrons are striking the target Normal peak target current is a milliampere or two for most tubes Many Electron Ray Tubes also have a triode section as well which is used as a DC amplifier in the application circuit Such triode sections are tested just like any other triode for emission transconductance heater to cathode leakage and gas Some tubes such as the EMM801 have two separate display sections and two triode DC amplifier sections All of these are tested independently and the results are shown on separate Results Screens Note that the transconductance of DC amplifier triode sections in Electron Ray Indicators is usually very low Sometimes it is as low as 0 05 or 0 1 mA V If such a tube is suspect the user is advised to try it in an application circuit to see if the shadow movement is adequate Do not rely on the Transconductance percent indication alone for Electron Ray Indicator tubes triode sections 4 4 RECTIFIER TUBES In the case of full wave rectifiers such as the 5U4 5Y3 and GZ34 a specialized results screen is displayed It shows the measured forward and revers
41. ontains a single upper case letter or a number 0 9 which denotes the functional type of tube such as Diode Triode Pentode etc The table below shows the code character for each tube types EJ T TABLE 6 1 TUBI z TYPE CODES A Diode F Rectifier G Triode L Tetrode P Beam Tetrode Q Pentode T Pentagrid Converter U 1 Electron Ray Indicator Indicator Section Tetrode or Pentode tested as a Triode Note that the correct Tube Type Code is necessary in order for the AT1000 to execute the proper tests for a particular tube or section type When the number 1 appears in the Tube Type Code field it causes the tube or tube section to be tested by connecting the Plate and Screen Grid together In this way Tetrodes or Pentodes will be tested in the Triode Connected Mode The voltage and current set for the Plate then apply to both the Plate and Screen Grid electrodes in the tube The Screen Grid power supply is left unconnected in this mode and the Screen voltage and current should be set to zero 6 3 SOCKET CODE The next Field 3 contains a single upper case letter which denotes which socket on the AT1000 will be used for the test The sockets are designated A through H and a letter will appear in this Field that corresponds directly with one of the sockets on the unit The sockets differ as follows TABLE 6 2 TUBE SOCKET CODES 4 pin small base pins 1 and 4 ar
42. operation LCD DISPLAY The backlit LCD display contains four lines of 40 characters each By observing the display the user is guided through mode and tube selections shown test setup information instructed which socket to use and shown the test results MENU NAVIGATION KEYS AND ENTER KEY Using these five tactile feedback keys the user navigates through the menus and makes selections as guided by the LCD Display The ENTER key is used to make a selected option active to confirm an operation and finally begin the actual test The left arrow lt key is used to abort a test or to go back to a previous menu The other keys are used to navigate up down and left and right in the List of Tube Types or to navigate through the System Menus AC INLET AND POWER SWITCH The unit is shipped wired for 115V or 230V AC 50 or 60 Hz operation Verify that your unit is wired for the correct voltage before connecting it to a mains source Connect the supplied AC line cord to the AC inlet on the AT1000 then plug the opposite end into a grounded outlet In countries other than the United States the use of an adapter or special power cable may be necessary Use the power switch to power up the unit or to shut down after testing operations are concluded Always switch OFF the power switch when you have completed a tube testing session Disconnect the AC power cord from the outlet if the unit will not b
43. sent at the Audio Out connector 3 0 BASIC OPERATION IN STAND ALONE MODE i The AT1000 is very easy to use Follow these instructions to test a tube 1 Plug the unit into a source of AC power Set the Power Switch to ON The fan will start and the firmware version is displayed momentarily The settings for Biasing Mode and Test Duration are displayed Then a list of tube type numbers appears 2 Use the UP DOWN LEFT and RIGHT arrow keys to move the cursor and navigate to the following screens The LEFT and RIGHT keys move the cursor along each line and up or down a line when the extremes of a line are reached Use the UP and DOWN arrow keys to go to the previous or next page The tube types are arranged alphanumerically with numbers coming before letters This means a 6550 will be found earlier in the list than a 6AQ5 The European letter prefix tubes like the ECC83 are listed after all the tubes that start with a number Tubes like the 6CA7 EL34 are listed in both places under 6CA7 and also EL34 The test setup is identical no matter which one is selected When the G ursor is position on the tube type number you want to test press the ENTER key 3 A screen is presented which shows some of the basic parameters of the test setup for the selected tube type Press ENTER again to confirm this is the tube you want to test 4 Next you will be prompte
44. stablishing a match between tubes Tube matching generally consists of testing a number of identical tubes and then grouping them by one or more tested parameters Tubes can be matched by emission transconductance or both If only one parameter is to be matched it is recommended that emission is selected For power output tubes some amplifiers have DC and AC balance controls These controls can null out some of the variance in tube parameters In parallel SEP and push pull parallel power tube operation close matching is essential for maximum performance There are generally no separate bias and drive controls when tubes are run in parallel and if the tubes don t share the AC and DC loads symmetrically power output and distortion will suffer greatly Differential audio and instrumentation amplifiers achieve best performance when matched tubes are used Quite often miniature dual triodes are employed These can have their sections matched or all the tubes in a signal chain can be matched The circuit topology dictates which is more important but full matching for this type of equipment guarantees best performance To match tubes by emission use the Fixed Bias Mode and compare the resulting plate currents measured during the test The closer the values the better the match In push pull power output stages the emission match should be within 5 if there is no DC balance control or separate bias adjustment for each tube
45. sults Use the UP and DOWN keys to move between the results screens for each tube section If the tube is only a single section type only one screen of results will be displayed no matter if the UP and DOWN keys are pressed 11 To test the same tube again just press ENTER The unit will ask you if you want to re test the tube Press ENTER once more to repeat all tests The heater is already on so there is no need to repeat the warmup After the tests complete the new results are displayed Each time the test is repeated the old results are replaced by the new results T 12 Press the lt key to exit the test back to the setup screen for the tube The heater will now turn off NOTE a second press of the lt key will be necessary in the case of rectifier tubes Allow the tube to cool and then carefully remove it from its socket For rectifier tubes it is recommended that the POWER switch be turned off before the tube is removed from its socket Using a circular rocking motion while pulling gently upwards helps to remove a tube without damaging the tube s pins or the socket Another of the same type of tube can be placed into the same socket and the test repeated including heater warmup by pressing the ENTER key The exception to this is rectifier tubes which will require selecting the tube type from the list again 3 1 NOTES ON TESTING 7 a Af
46. t arrow key until the copyright screen disappears Then release the left arrow key The top level System Menu is displayed 8 2 SELECTING A SYSTEM SUB MENU Use the left and right arrow keys lt and gt to scroll through the different selections The various System sub menus and selections are as follows Computer Control Mode Change Biasing Mode Upload New Tube Data Firmware Upgrade BootLoader Change Test Duration Calibrate Rectifier Test Return to Tube Testing When the desired sub menu or function is displayed press ENTER to select it Two of the selections Change Biasing Mode and Change Test Duration will subsequently lead to sub menus where additional options are available to select These selections will cause the unit to enter the displayed mode immediately when ENTER is pressed 8 3 COMPUTER CONTROL MOD Gl When Computer Control Mode is displayed at the top System Menu and ENTER is pressed the unit immediately goes into the Remote Control Mode From this point on it responds primarily to commands over the RS232 serial port Some of the keys on the AT1000 have specific functions while testing tubes under computer control 8 4 CHANGE BIASING MOD Gl When Change Biasing Mode is displayed and the ENTER key is pressed a sub menu is displayed Using the scroll keys lt and gt make a selection of either Fixed Bias or Auto Bi
47. t between 1 and 4 This digit tells the AT1000 information about which section in the tube the line applies to If the digit is a 1 it is the last or the only section inside the tube envelope If the digit is 2 this is the second section in the tube 3 and 4 designate the third and fourth sections contained within the same envelope In the case of tubes with multiple sections the test for each section takes up one Record in the test data file These lines or records are always located one above the other The first Fields of the Records that comprise the tests for a multi section tube are always the same as it is the Tube Type Number e g 12AX7 With multiple section tubes several other fields are often duplicated as well For example with a 6T8 the Heater Code and the Socket Code is identical for each of the four sections This is because the tube remains in the same socket and all the sections share a common heater The Section Identification Field must decrement with each successive section on each successive line record The final section of a multiple section tube is last and its Section Identification Field is ALWAYS a 1 Tubes with only one section like the 6V6 and 2A3 always have only one line of test data one record and always have a Section Identification Field entry of 1 There are several dual section identical triodes like the 12AX7 12BH7 ECC81 etc These tubes have two lines of test data and you mi
48. ter the ENTER key is pressed in Step 4 no user action is required until the test concludes at Step 10 UNLESS THE UNIT IS SET TO CONTINUOUS MANUAL TEST MODE In Manual Test Mode the user must be careful when testing high power tubes as the B regulators in the unit are subject to overheating Should they overheat B will be turned off and a message to this effect will be displayed on the LCD For more information see section 5 2 b The user can bypass the remainder of the heater warmup after the ramp interval by pressing ENTER Normally you should allow the complete warmup time to elapse and not use this function c During bias adjustment plate current may over or under shoot slightly This has virtually no effect on test results and is caused by slight instabilities or noise in some tubes Some tubes will appear to be more stable after they have been run for a while The Manual Test Mode allows a longer run time for the tube than does the Timed Test Mode d Any time B is applied to the tube the AT1000 protects itself by shutting down if a short or overload condition occurs In this case the user is notified by a message that a short or overload has been detected The user can either restart the test or bail out back to the Test Setup menu If a second attempt at testing a tube causes another short overload shutdown the tube should be considered defective and disposed of
49. ther the Biasing Mode or the Test Duration 9 0 USING THE TUBE TESTING AND CURVE PLOTTING SOFTWARE TubeTest is the test and curve plotting software which runs ona personal computer and allows extensive tube testing and curve plotting functions Results can be saved and retrieved and printed Test setups can also be saved and recalled In addition to the heater cathode leakage emission transconductance and gas tests which the AT1000 performs in stand alone mode the software is able to provide even more information A user can also obtain plate resistance and Mu and grid leakage is directly displayed down to 01 uA Please refer to the separate documentation to install configure and use TubeTest with the AT1000 10 0 BIASING AND TESTING MODES Firmware Version 2 0 and later offers two different Bias Modes and two different Test Modes This section will explain these These two modes of operation are selected from the System Menu See section 8 0 for instructions on how to use the System Menu and sub menus to change these mode settings Note that after the Biasing and Testing Modes have been changed the unit remembers which mode s it s set to even if AC line power is disconnected 10 1 BIASING MODES There are two modes of bias adjustment that the AT1000 can use These are called Auto Bias and Fixed Bias The difference between these modes is reflected in what happens
50. ties and drift radically during operation The warping can even get so extreme that short circuits can develop between electrodes Other tubes often vintage military specification tubes are conservatively designed and well constructed and remain stable even after many thousands of hours of operation Equipment that operates its tubes at or near the Absolute Maximum Ratings is more likely to cause heat damage to its tubes over time Drift can be measured by using the Manual Test Mode where any such drift is apparent over time Just be careful with power tubes as they can cause the AT1000 B regulators overheat in just a few minutes 5 0 TROUBLESHOOTING Refer to this section if you are having difficulties with the AT1000 5 1 Tube tests bad with no or very low emission or transconductance Try a known good tube in the unit If a known good tube tests bad the AT1000 may have a problem requiring repair 5 2 Test always cuts off showing possible short or excessive gas Try the test without a tube in the socket If it shuts down again with errors about shorts or gas there may be a problem requiring repair If B stays on without the tube then the tube was defective 5 3 Heater or Filament inside tube does not light The Heater or Filament could be burned out Try another tube If the problem persists contact the factory for instructions 5 4 LCD Display backlight does not light fan does not run
51. uld select the Fixed Bias mode on the AT1000 The choice between Auto or Fixed Bias also interchanges what you should look for when evaluating emission test results In Auto Bias a strong tube will produce a higher grid voltage larger negative voltage than a weaker one even though both might show the same plate current and same or close transconductance Conversely in Fixed Bias mode a strong tube will show a higher plate current than a weaker one Auto Bias Look at Grid Voltage Result higher voltage greater emission Fixed Bias Look at Plate Current Result higher current greater emission 10 3 TESTING MODES There are two modes of testing available With Timed Automatic Mode the microcontroller inside the AT1000 performs each test automatically in sequence without operator interaction In Manual Continuous Mode the user has control over how long the tube operates and stablizes before results are collected for both Emission and Transconductance 10 4 TIMED AUTOMATIC TEST MODE In Timed Automatic Mode the user only needs to insert a tube into the proper socket and press ENTER Then the unit does the following 1 Heater warms up for 60 seconds cathode type or 15 seconds directly heated type 2 B is applied and then either Fixed or Auto Bias is used to obtain current flow in the tube 3 The Transconductance test starts and runs for eight seconds during whic
52. using the System Menus see section 8 0 7 Once the plate current is flowing the unit will proceed automatically to test the transconductance if it is in Timed Test Mode If the unit is configured for Manual Test Mode the user is prompted by the LCD display to Press ENTER to continue This allows the user to wait until plate current stablizes if desired before continuing with the Transconductance Test The user can change the unit between Timed and Manual using the System Menus see section 8 0 Test Modes by A 1 kHz sine wave is applied to the grid of the tube The AC plate current is measured and the tube s transconductance is calculated and displayed Firmware Version 2 08 and later displays updated Plate and Screen Current while the Transconductance is being measured This increase in Plate Current which is normal is due to the fact that the tube is amplifying a 1kHz signal The Plate Current is measured for the Results Screen BEFORE the 1 kHz signal is applied so that an accurate Measured Plate Current reading is obtained If the unit is set for Timed Test Mode it will measure and average transconductance for 8 seconds and then move on to the next gas test If the unit is configured for Manual Test Mode it will prompt the user with the Press ENTER to continue message This is useful if you want to see if the transconductance drifts over time In Manual Test Mode the u
53. will show zero leakage but a few microamperes is probably OK Heater to cathode leakage is critical for a preamp tube or a tube used in a cathode follower or in a cascode circuit It is less critical for a power output tube or one that has its cathode tied to ground in the Circuit b Second Line This shows the specification values of grid voltage in Auto Bias Mode or plate current in Fixed Bias Mode and transconductance GM which is displayed in milliamperes per volt Multiply by 1000 to convert mA V into uMHOs c Third Line This line shows the actual values of grid voltage in Auto Bias Mode or plate current in Fixed Bias Mode and the transconductance that were measured during the test See section 10 0 for a description of the difference between Auto Bias and Fixed Bias In Auto Bias Mode if the actual grid voltage is less than specification this means that the emission of electrons from the cathode was weaker than expected and a correspondingly lower grid voltage was required to establish correct plate current In Fixed Bias Mode if the actual plate current is less than specification this also means that the emission is weak In Auto Bias Mode if the actual grid voltage was higher than the specification value this means that the tube has strong emission and can be expected to have a good amount of life remaining If the actual grid voltage is very low or is zero the tube is bad and should be replac
54. y mean the tube is defective This is because these parameters are not closely controlled in these types of tubes d Fourth Line This line shows three things On the left a percentage of Emission is shown 100 is displayed if the tube has emission that matches the specification value 80 means that the tube has only 80 of the emission specified in the data sheets A tube with an emission of greater than 100 shows that the tube has good emission and should be expected to perform well in the application circuit In the center of the fourth line a percentage of Transconductance is shown 100 means that the GM of the tube was the same as shown in the data sheets A reading of less than 100 means that the tube s transconductance is only that percentage of what the data sheet shows As for Emission a GM percentage over 100 shows that the tube is performing better than specification The percentage values shown makes it easy to tell at a glance whether the tube is good weak or excellent You may ask what constitutes a good tube Well this is difficult to say and depends more upon your own criteria In the days when vacuum tubes were the mainstay most component values and supply voltages could be off as much as 20 and the equipment would still work satisfactorily You can apply this rule to a minimum acceptable Emission and Transconductance of 20 low or a display of 80 Tubes showing emission or GM less than
55. y require some trial and error to optimize the test The EMM801 is a rare dual indicator similar to an EM84 It was used as a level indicator in stereo tape recorders This tube has an additional grid which appears to be intended as a brightness control However this extra grid also affects the operation of the triode DC amplifier sections This grid must be connected to ground when the DC amplifier triode sections are being tested to obtain a repeatable plate current Dealing with these extra electrodes in Electron Ray tubes can be a challenge The manufacturer s data sheets even when available often do not describe the extra electrodes enough to design them into a test 6 15 PREPARING THE TEST DATA FILE FOR UPLOADING You will probably want to insert any new tubes you add into the list while maintaining the alphanumeric format The AT1000 lists tubes in the order they appear in the TubeData File When directly editing the CSV file with a Notepad just place the cursor at the far left on the line below where you want to add a new line Record and press ENTER on the keyboard A blank line will then appear The last character in the last Record in the file must be the exclamation Point This is necessary because it tells the AT1000 that the End of File was reached Do not add a comma between the last character and the exclamation point in the CSV file 7 0 UPLOADING THE TEST

AT1000 User Manual - Amplitrex Audio Products

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