The Triode Board
Contents
1. 1K 1 2W MF power e g BC formerly Philips PRO1 Use 2K2 for alarm at higher current see Section As R1 R3 24V relay option R28 10K F 543 068 F 543 147 F 333 712 F 543 380 F 337 857 F 543 500 F 543 627 F 987 750 F 543 860 R27 15V 0 3 0 5W zener e g BZX79C15 or 1N4109 etc See Section Bourns 3306P series or Bourns 3309 series NB not available below 100R Bourns 3306P series or Bourns 3309 series NB not available below 100R Bourns 3306P series or Bourns 3309 series Bourns 3306P series or Bourns 3309 series 34 F 544 103 Stock Nos See catalogs See catalogs F 108 235 F 452 580 F 108 239 F 452 622 1999 2003 IFWtech Limited Triode Board Parts List Semiconductors etc not supplied in kit Total Part No Type A PIV W Comments Stock Nos 1 BR1 AM152 1 2A 100 200V F 330 7918 sl DK RB152DI ND 2 D1 D2 GI750 6A any PIV 400A surge rating F 364 940 DK 6A05MSCT ND 5 D3 D4 D11 1N4001 1A Or any higher F 251 677 D12 D13 numbered 1N400x 5 D6 D7 D8 1N4148 F 368 106 D9 D10 1 D5 1N5337B 4 7V SW F 933 119 1 K1 8A 2PCO 12VDC Schrack or Potter amp F 625 589 Brumfield RTE24012 DK PB296 ND 24V relay option use Schrack or Potter amp F 625 590 RTE24024 Brumfield RTE24024 DK PB297 ND 2 LED1 LED3 Red Normal 20mA GRID HV and ANODE indicator 1 LED2 Green Normal 20mA READY indicator 17 LED4 Blue Normal 20mA TX indicator Yellow 22. TO CATHODE RV4 10K 10K Practical Modification Two V24ZA50 VDRs in series Cut track insert 10k As you see the modification could hardly be easier The only difficulty is fitting two VDRs into the available space You may need to relocate RFC2 off the board Triode Board AN 2 39 Issue 1 5 for board v2 4 January 2003 Remove TL431 U2 Bend up RH leg and re insert Twist U2 so you can insert 15V zener diode cathode band down into vacant hole Solder zener to bent up leg and solder 100nF across to leg of R9 note correct orientation of R9 1999 2003 IFWtech Limited The Triode Board THE TRMODE BOARD dte 1999 2003 IFWtech Limited
3. TO CATHODE RV4 10K Optional TO METERING The cathode bias voltage is normally adjustable in the range from 3 to 27V which suits most tubes including the 3 500Z 3CX800 and 8877 For tubes such as the GS35b and GS31b which can require more than 30V bias at high anode voltages you can insert an extra resistor as shown However experience shows that the voltage required is higher than anticipated and can exceed the 36V breakdown voltage of the TL431 2 Increasing the Bias Voltage This note gives a simple modification to moves the range of bias adjustment up to 27 45V This is plenty high enough for the Russian triodes even at extreme anode voltages The modification is simply to insert a zener diode in series with U2 This reduces the voltage across U2 but it does not affect the voltage regulation because the zener is inside the DC feedback loop The schematic is shown on the next page ZD is a BZX79C15 zener diode and C is a 100nF bypass capacitor to remove any avalanche noise from the diode The resistor R inserted by cutting the track as shown in the manual is increased to 10kQ The optimum VDR combination for this bias voltage is two V24ZA50s in series This combination will not start to conduct over the available voltage range which could be a problem with some samples of the 33V VDR previously recommended Triode Board AN 2 38 Issue 1 5 for board v2 4 January 2003 1999 2003 IFWtech Limited Appendix 1
4. THE TRIODE BOARD v2 4 9 IN u ce RFC2 M u U BRE R JE Sia T g n C5 CATHODE Ek DE BCE a a1 R31 22 D12 gg EE m a RFCS R24 OU be m A Loy S14 O u Ce 2 HV CTRL g 3 Alal us C zas Ortr_ D 0 a UNREG o APCS Triode Board AN 2 32 Issue 1 5 for board v2 4 January 2003 1999 2003 IFWtech Limited There are many sources for most of these components The Stock Nos columns show mostly Triode Board Parts List Farnell order codes F and some from Digi Key in the USA DK Farnell http www farnell com uk have associate companies in many countries including Farnell Chicago 1 800 718 1977 note that US order codes may differ Mouser Electronics and Digi Key are also good sources in the USA Resistors and capacitors may be subject to minimum order quantities Small quantities can often be bought more cheaply from other dealers e g Maplin in the UK Capacitors Total C No C19 C8 C9 C11 C12 C13 C17 C20 C3 C4 C1 C2 C6 C7 C10 C14 C15 C16 C21 C22 C24 C25 C26 C5 C18 C23 Resistors R in resistor values means O e g 15R 150 Total 1 1 R No R2 R1 R3 Value 100pF 470pF 10n 0 01uF 10n 0 01uF 100n 0 1uF 1uF 100uF 4700uF Volts at least 16 16 16 200 63 50 16 35 Value R Q W 0R33 0R47 or 5W 1RO 2R2 3R3 4R7 5W
5. 5 for board v2 4 January 2003 1999 2003 IFWtech Limited 8 Power Up CAUTION When you install the Triode Board in your amplifier take care not to change any of the calibration adjustments that you have already made to RV1 RV5 8 1 First Switch on Since you have already tested the Triode Board off line before you built it into the amplifier Section p there should be no surprises when you first switch the whole amplifier on What to expect 1 When you first switch on the blower should start the heaters should begin to warm up and the warm up timer will start Only the two red ANODE and GRID HV LEDs will be lit 2 When the warm up period is complete the ANODE LED will go out the HV CTRL line will come up and the HV mains relay will close At this moment the GRID HV LED will still be lit because there is no HV yet 3 A few moments later when the step start has operated and the HV comes up the GRID HV LED will go out and the green READY LED will come on 4 The two red LEDs will not light again unless there is a fault The amplifier is now in its standby condition with the tube cut off 8 2 Cathode Bias Adjustment 1 Set the transceiver to SSB with VOX switched off and MIC gain set to zero 2 Press the PTT The yellow or blue TX LED will light and the anode current will rise to its zero signal level 3 Although you pre set the approximate cathode bias voltage in Section the current will probably no
6. 6R8 or 15R 2R2 or 3R3 5W Comments Ceramic 0 1 radial leads Ceramic 0 1 radial leads Multilayer ceramic 0 2 radial leads Ceramic disk 0 2 radial leads Multilayer ceramic 0 2 radial leads Electrolytic 0 1 radial Electrolytic 0 1 radial Electrolytic Panasonic TSUP 0R33 0 330 3K3 3 3k 92 1M0 1 0MQ etc Comments Vertical mounting e g F SQM5 series Mouser have similar Stock Nos F 237 048 F 237 127 F 750 840 F 219 496 F 750 992 F 920 691 F 920 435 F 652 088 DK P6905 ND Stock Nos See catalogs 5W axial lead mounted vertically e g DK YAGEO series See catalogs The kit includes a total of 9 resistors for R1 R3 Select 3 using the table on page 12 Triode Board AN 2 Issue 1 5 for board v2 4 January 2003 33 1999 2003 IFWtech Limited o z See catalogs Total R9 R8 R30 R31 R32 R33 R5 R7 R4 R24 R6 R11 R13 R14 R25 R34 R10 R12 R15 R16 R17 R18 R19 R20 R22 R23 R26 R27 R28 R29 R21 RV No RV1 RV2 RV3 RV4 RV5 Triode Board AN 2 Issue 1 5 for board v2 4 January 2003 Triode Board Parts List 47R 100R 470R 1K0 1K0 3K3 10K 10K 100K 1M0 Value 5K 2K 500R 200R 50R or 20R see text 10K 5K 1K 500R 100R or 50R see text 500R 10K 0 25W 0 25W 0 5W 0 25W 1W 0 25W 0 25W 5 7W 0 25W 0 25W Comments 24V relay option R30 R32
7. Issue 1 5 for board v2 4 January 2003 1999 2003 IFWtech Limited shown in Figure 2 below the entire arc return current flows through the meters for grid current and anode current This can destroy the meters unless they are protected CURRENT LIMITING RESISTOR ARC internal or external through both meters Figure 2 Arc or flashover from HV to chassis can destroy grid and anode current meters There are three basic kinds of protection against anode current surges Use a current limiting resistor in the HV line to limit the maximum possible surge current See Section 7 2 3 for details YOU MUST USE THIS VITAL SAFETY COMPONENT Use protective diodes around the meters both to protect the meters and to clamp the HV minus rail close to chassis potential The Triode Board does this e Switch off the HV transformer to minimize the follow on energy after the arc begins The Triode Board allows you to do this and it can save greatly on interruptions in operation due to blown fuses Arcs often do not recur and in many cases you can resume operation by simply pressing the RESET button which brings up the HV again 3 2 2 Meter Scaling and Protection Grid and anode current meter ranges vary widely between different amplifier designs according to the type and number of tubes involved However the protection reguirements are always the same Figure 3 next page shows two basic ways of metering 500mA of anode curr
8. M1 M2 Meters see text 1 Q1 TIP147 100V 10A PNP Darlington B C E F 434 7894 pinout 5 O2 03 Q5 ZVN3306A 60V 5A N MOSFET S G D F 352 901 Q7 Q8 RAS om 50 pinout 1 Q4 IRF9530N 100V 13A P MOSFET G D S F 934 616 Rdsoy 0 292 pinout 1 Q6 MPS2222A 40VNPN E B C pinout F 682 214 hee 100 min 2 RFC1 2 15uH4A Siemens B82111 B C23 or equivalent F 505 870 ferrite cored RF choke end mounted 2 RFC3 4 30uH Siemens miniature toroid RF choke F 312 4873 500mA or similar 1 SW1 Push switch SPST 1 TI 15V AC 1A For 24V relays use 20V AC 1 U1 4N36 Current transfer ratio 100 10mA F 326 069 1 U2 TL431CZ 2 5 35V Adjustable zener F 571 120 ce DK LM431ACZ ND Triode Board AN 2 35 Issue 1 5 for board v2 4 January 2003 1999 2003 IFWtech Limited Triode Board Parts List 1 U3 LM555CN Must be CMOS F 409 340 1 U4 4011 CMOS 4 x 2 input NAND gate F 573 632 1 U5 4023 CMOS 3 x 3 input NAND gate F 384 835 1 U6 MC7812CT 12V 1A reg F 492 190 2 VDR1 V24ZA50 Harris GE or For high bias option F 318 346 Panasonic gt 30V use two VDRs in DK P7317 ND series see page Hardware etc not supplied in kit Total Part No Type Comments Stock Nos 1 none TO218 heatsink 01 Transistor outline also known see text User to as SOT93 or TO3 P provide 1 none TO218 mounting kit User provides nut amp bolt F 522 648 01 No grease reguired 1 none TO 220 heatsink U6 No insulating washer F 170 070 required User pro
9. current R2 is the anode current metering resistor and its value is chosen to give approximately 0 5V drop at full scale anode current The nearest standard resistor values are used R3 is the anode current sensing resistor For one large tube or two smaller tubes use 2 20 for R3 This allows RV5 to set the anode current trip in the range 0 9 1 4A For one smaller tube use 3 30 for a 0 6 0 9A current limit The table below shows typical full scale values for grid and anode current meters using various combinations of popular tubes and also the values of R3 and cathode bias voltage Tube s Ig max R1 la max R2 R3 Bias typical One 8877 200mA 3R3 1 5A 0R33 2R2 8 12V One GS31 35b 400mA 2R2 1 5A 0R33 2R2 24 30V Two 3CX800 100mA 6R8 1 5A 0R33 2R2 5 1 8V One 3CX800 50mA 15R 1 0A 0R47 3R3 5 1 8V Two 3 500Z 350 or400mA 2R2 1 5A 0R33 2R2 9V One 3 500Z 1500r200mA 4R7 0 75A 1RO 3R3 9V Triode Board AN 2 12 Issue 1 5 for board v2 4 January 2003 1999 2003 IFWtech Limited Industry standard 5W end mount resistors are recommended for R1 R3 and are supplied in the kit The kit includes nine 5W resistors of various values enough for any of the above options you will have six resistors left over You can also use normal axial lead power resistors mounted vertically 4 2 Choosing and Using Meters You can use a wide variety of meters for grid and anode current and the calibration resistors on the Triode Board will make them read c
10. instant heat tubes you still need the warm up timer because the circuit will not initialize correctly without it 3 9 RFI Protection The unshielded layout of many amateur power amplifiers can lead to large stray RF voltages on the wiring This applies particularly to amplifiers for HF and for 50MHz which often do not have totally shielded and bypassed RF compartments The Triode Board is designed for high immunity against RF interference RFI The PC board has both top side and bottom side groundplanes wherever possible and the board can be grounded to the chassis at all four corners The design uses high level CMOS logic for optimum RF immunity and critical external connections are protected by RF chokes and bypass capacitors There are many RF bypass capacitors on the board with provision to add even more bypassing if needed The Triode Board has been tested in amplifiers from 1 8MHz to 1 3GHz in some extreme RFI situations but we cannot guarantee RFI immunity in all situations We will be pleased to help if you find any difficulties contact details in Section p 4 Using Your Tubes and Meters You can use the Triode Board with a wide range of tubes and also a wide range of panel meters for grid current and anode current 4 1 Which Tube or Tubes Your choice of tube or tubes affects several components R1 is the grid current metering resistor The value is chosen to give approximately 0 7 0 8V drop at full scale grid
11. strongly recommend that you use the anode current protection relay in the HV transformer primary The rest of these instructions assume that anode current protection is present Triode Board AN 2 9 Issue 1 5 for board v2 4 January 2003 1999 2003 IFWtech Limited the na relay K1 lights the red GRID HV alarm LED and turns off the green READY LED The GRID HV alarm is automatically reset when you release the PTT button or when the transceivers VOX delay times out This will allow you to resume operating if the low HV condition was only intermittent e g a brief drop in AC mains voltage If the HV is still low the circuit will trigger again to protect the tube WARNING Damage to the grid may occur if you apply RF drive while the amplifier is in a fault condition 3 4 Cathode Bias For low intermodulation distortion the cathode bias needs to be as constant as possible Also the bias needs to be adjustable to set each individual tube to the manufacturer s recommended no drive idling current Conventional high power zener diodes have several disadvantages they are not adjustable their voltage tends to rise significantly with anode current and diodes large enough to survive anode current surges can be quite expensive Other solutions such as forward biased rectifier diodes give even poorer bias voltage regulation The Triode Board uses a true constant voltage bias regulator which is fully adjustable page so you can set the
12. 000 trimpot the value supplied with the kit will probably be OK and would be easier to adjust For intermediate value meters such as 500uA adjust all values in the table proportionally As the current goes down all the resistance values go up 4 2 2 Higher current Meters What if you have some 100mA meters or higher The bad news is that I don t recommend using these without modification The good news is that if you open up the meters you ll probably find that they contain an internal shunt resistance between the terminals If you remove this shunt the basic meter movement will probably be something like 0 1mA or 0 10mA which should be OK for the Triode Board 4 2 3 Re scaling Meters You probably won t find meters with the correct scale values so you will need to alter the scale There are various options starting with the easiest Triode Board AN 2 13 Issue 1 5 for board v2 4 January 2003 1999 2003 IFWtech Limited Do nothing re scale the meters in your head whenever you look at them This is definitely the easiest but your friends in the contest group may find it confusing e Change the units for example you can convert a 0 1mA meter to read 0 1A by carefully erasing the m in mA Change by factors of 10 either erase some zeros on the scale or add more zeros using matching rub on numbers Keep the existing scale arc but change all the numbers e Re draw the complete mete
13. 03 IFWtech Limited 2 Introduction 2 1 What You Get To give you the best possible value for money we do not supply expensive off board components such as meters transformers and large heatsinks You can probably find these components much more cheaply as surplus The full Triode Board kit includes 1 The PC board double sided with plated through holes and printed component locations 2 Allthe on board components premium quality for reliability To cover almost all possible combinations of tubes and meters the kit includes a range of resistors of various values 3 Power transistor Q1 and mounting kit but not heatsink 4 Push on tags for board connectors 5 Complete schematics and this User Manual The bare board option is the Triode Board with this same User Manual 2 2 What You ll Need Most of these additional components are easier to buy surplus than at new prices so we didn t include them in the kit See Section Bffor more details about these components 1 RESET switch SPST momentary push button low voltage 2 STATUS LEDs two red one green one yellow or blue all ordinary 20mA types See Section p 4 for details of how to build the LED array 3 Heatsink for A1 4in x 3in x 1in or equivalent 2 C W or less For low bias voltages and lower power tubes you can mount Q1 on a cool area of the chassis 4 Metal mounting pillars and hardware for the PC board 5 M1 grid current 0 100uA mov
14. 25Q per kilovolt of HV In practice 50Q is a typical value Some circuits show 10Q or 209 but feel this may be too low for anode supplies of 3kV or more The resistor needs to be physically large both to handle the power dissipation in normal use and to avoid flashovers along the resistor body in the event of an arc A 50Q resistor ina 1A supply will be dissipating 50W key down so this is really a minimum acceptable rating Always choose a longer bodied resistor in preference to a short stubby one of the same rating 7 3 CHASSIS GROUND Connection WARNING The CHASSIS GROUND connection is vital for safety Do not rely on metal mounting pillars for safe grounding Connect the CHASSIS GROUND terminal using heavy wire it may need to carry up to 40A in an anode current surge Ground the wire to a large reliable ground lug firmly bolted to the chassis 7 4 RFI Suppression The Interconnections 2 diagram on page 29 shows some extra RFI suppression components that you might need to fit outside the Triode Board itself C102 and C103 can be connected directly across the two meters if needed If RFI is particularly severe you should consider the possibilities for better RF screening and also the use of shielded wire for meter connections etc Keep all connecting wires close to the chassis or panel and as far away as possible from RF components such as the tube and the RF input and output circuits Triode Board AN 2 25 Issue 1
15. 400x Triode Board connections or 24V DC EO O CHASSIS TO HEATER gt TRANSFORMER European component markings T101 15V AC 1A for 12V relays R in resistor values means O 20V AC for 24V relays e g 15R 150 0R33 0 330 Also 3K3 3 3kQ etc Triode Board AN 2 28 Issue 1 5 for board v2 4 January 2003 1999 2003 IFWtech Limited SAFETY RESISTOR HV SUPPLY R104 47R 50W gt Switched mains HV xx supply see Section 7 2 gt HV minus SAFETY RESISTOR R105 1K 10W To K101 lt European component markings R in resistor values means Q e g 15R 15Q 0R33 0 339 Also 3K3 3 3kQ etc Triode Board AN 2 Issue 1 5 for board v2 4 January 2003 Triode Board Interconnections 2 FS105 HV I O 1 2A HV GROUNDE D GRID hl OBA HV DIVIDER see Section 5 4 TRIODE U Each resistor i A 1M 0 5W 350V I Use 8 for 2 0kV 12 for 3 0k V I 12 for 4 0kV etc I R106Z off load voltages 1 To cathode or filament transformer center tap O CATHODE HV OK R107 R108 Both 100K 1W CHASSIS GROUND HV MINUS HV CTRL ANODE CURRENT M2 GRID CURRENT M1 b C102 10nF O Pa A ME TIP147 on heat sink TO LED ARRAY AND RESET SWITCH see Sheet 2 and Section 5 3 FROM T101 CONFIGURE FOR EXT RELAYS 1999 2003 IFWtech Limited CATHODE HV MINUS D2 GI750 D1 GI750 CHASSIS GROUND RFC2 O
16. C4 10nF 200V RFC1 O C3 10nF 200V R4 1K0 2W D5 1N5337B R3 2R2 or 3R3 W European component markings R in resistor values means e g 15R 150 0R33 0 330 Also 3K3 3 3kQ etc Triode Board AN 2 Issue 1 5 for board v2 4 January 2003 ANODE CURRENT Triode Board Schematic Sheet 1 R10 10K 5W KIA R5 1KO C5 EI 1u 16V VDR1 V24ZA70 GS35 31 V33ZA70 UtA 4N36 6 gt NAP se K C Sheet 2 E 4 10K RV4 I THE TRIODE BOARD Q E v2 4 990901 c IFWtech SN Sheet 1 of 2 Qi TIP147 HIGH BIASONLY TO Q6 BASE UNREG BR1 2A BRIDGE 12V DC reg AC IN 3 R34 C24 C25 10K 100n 100n 30 1999 2003 IFWtech Limited From UNREG From 12V reg Grid current R6 C10 7100n Triode Board AN 2 Issue 1 5 for board v2 4 January 2003 Triode Board Schematic Sheet 2 24V relays Cut make From 12V reg lt C16 m 31 1 2 3 6 8 K1 12V 2PCO 1N4001 D13 ZVN3306 RESET GRIDHV READY ANODE TX RFC as O HV CTRL C22 I 100n NO KIB THE TRIODE BOARD v2 4 991014 c IFWtech Sheet 2 of 2 European component markings R in resistor values means Q e g 15R 15Q 0R33 0 339 Also 3K3 3 3kQ etc 1999 2003 IFWtech Limited Triode Board Layout Actual size 5 7 x 3 3 in 145 x 84 mm R12 BIAS VDR1 K1 HI B
17. Grid and Anode Current Metering Grid and anode current metering is achieved in the normal way by connecting the meters between the chassis cathode and HV minus B minus rails Figure 1 shows how this works ANODE CURRE v ANODE CURRENT GRID CURRENT Figure 1 Grid and anode current metering Notice that only grid current flows through the grid current meter and only anode current flows through the anode current meter It s hard to believe but at least one amplifier manufacturer fails to get this right 3 2 Meter and Surge Protection Any power amplifier needs several levels of protection for your tubes meters HV transformer and above all YOURSELF 3 2 1 Anode Current Surges Nobody knows why sudden anode current surges happen they re over too guickly Reasons suggested include sporadic releases of gas into the vacuum inside the tube microscopic whiskers of metal inside the tube stray hairs or insects outside the tube spurious renegade photoelectrons no kidding line voltage surges parasitic oscillations intermittent antenna connections cosmic rays The important thing is that sudden anode current surges do happen and many people have learned what damage they can do All this damage is preventable The worst surges are arcs or flashovers These can occur either inside or outside of the vacuum envelope of the tube and lead to a near short circuit from HV to chassis As Triode Board AN 2 6
18. HV alarm LED should come on Check that PTT is locked out until the HV OK voltage is restored and also the PTT line has been un grounded Switch off Re connect the link from HV OK to UNREG and leave it connected until this checkout procedure is complete 6 3 2 Grid Current Alarm 1 6 3 3 9 Reconnect the temporary grid current setup as shown in Figure 9 Set RV3 to mid travel Apply power and let the warm up timer complete Only the green READY LED should be lit Inject a simulated grid current and set it at the level where you want the circuit to trigger full scale on the meter is usually a good point Turn RV3 slowly clockwise until the red GRID HV LED lights and the green READY LED goes out Reduce the test current and the light should go out Repeat the adjustments until the circuit triggers exactly where you want it to Remove power and remove the temporary wiring Anode Current Alarm Reconnect the temporary anode current setup as shown in Figure 10 Set RV5 fully counter clockwise Apply power and let the warm up timer complete Only the green READY LED should be lit Inject current and set it at the level where you want the circuit to trigger again full scale on the meter is usually a good point Turn RV5 slowly clockwise until the red ANODE LED lights the green READY LED goes out and the HV CTRL output drops to zero Reduce the test current and the status should stay the same until you press the
19. RESET button Repeat the adjustments until the alarm operates exactly where you want it to remember that you need to press RESET each time If the alarm operates at too low a current change R24 to 2 2kQ Remove power and remove the temporary wiring 6 3 4 Warm up Timer 1 If you are using the normal value of 1 0MQ for R21 and had connected a temporary 47kQ resistor in parallel with R21 to shorten the warm up time then remove that resistor now 2 Apply power and check that the warm up timer takes approximately 3 minutes to complete with R21 1 0MQ C18 100uF Triode Board AN 2 22 Issue 1 5 for board v2 4 January 2003 1999 2003 IFWtech Limited This completes all the off line tests The Triode Board will now be calibrated and ready for use Triode Board AN 2 23 Issue 1 5 for board v2 4 January 2003 1999 2003 IFWtech Limited 7 Interconnections The Interconnections diagrams on pages 28 and 29 show all the connections to the Triode Board and some recommended circuits for the rest of your amplifier Note part numbers on the Interconnection diagrams start at 101 to distinguish them from part numbers on the Triode Board 7 1 Mains Power Control The mains power control components discussed below are shown in the Interconnections 1 diagram on page P8 7 1 1 HV Power Control The HV CTRL terminal provides 12V DC to a mains power relay in your HV supply 24V DC if you made the 24V relay modificati
20. THE TRIODE BOARD Control and Protection for your Triode RF Power Amplifier All the hard work done e Protects your triodes e Grid and anode current metering e LED status indicators e Warm up timer e Adjustable regulated cathode bias e TX RX switching and relay supplies e Simple wiring to one PC board e Easy to build clear how to instructions in this User Manual Versatile Use with one or two tubes including 3 500Z 3CX800 8877 3CX1500 GS35b GS31b GI7b TH308 YD1336 Triode Board AN 2 Issue 1 5 for board v2 4 January 2003 1999 2003 IFWtech Limited WARNING These notes are intended for users who have sufficient experience to work safely with high voltage circuits X Use at your own risk We cannot accept responsibility for any damage or injury DANGER AC mains voltage and high DC voltages REVISION NOTES AN 2 Issue No Triode Board Issue No Revision Details 1 0 September 1999 2 4 Revised after extensive pre release testing first production boards 1 1 October 1999 2 4 R24 changed to 3K3 note about HV metering 1 2 April 2000 2 4 Minor updates and typos change of Internet and WWW addresses 1 3 January 2002 2 4 Minor updates to component list 1 4 April 2002 2 4 Updated components list and part numbers in schematics and main text 1 5 April 2002 2 4 Reformatted to A4 new US distributor included AN 5 as Appendix 1 European Component Markings R in resist
21. and it takes care of all tolerance variations 8 8 If the full scale voltage drop across the shunt resistor is close to 0 5V protection diodes will be highly effective because they start to conduct heavily at about 0 6V The schematic on page BO shows the metering circuits in the Triode Board for grid and anode currents Section Klexplains how to choose meters and metering resistors for your particular amplifier Page 30 also shows how the meter protection in the Triode Board works Diodes D1 and D2 divert anode current surges safely around the meters and also clamp the HV minus rail close to chassis potential The surge is finally stopped when the HV supply is interrupted by either the sensing circuit see below or a blown fuse D1 and D2 need to have a high surge current rating ordinary 1A rectifier diodes are marginal so this design uses big 6A diodes with a surge current rating of 400A An anode current surge flows in the opposite direction to normal grid current so diodes D3 and D4 are included to also protect the meter M1 against excessive forward grid current Triode Board AN 2 8 Issue 1 5 for board v2 4 January 2003 1999 2003 IFWtech Limited 3 2 3 3 3 3 3 1 3 3 2 3 3 3 Anode Current Protection This section gives more details of the anode current protection circuit See the schematics on pages 30Jand af In order not to interfere with anode current metering the protection circuit senses anode curr
22. atively you can use a variable voltage current power supply 3 Apply power and adjust the current to a known value Then adjust RV2 to give the same reading on your meter scale 4 This completes the calibration of the grid current meter Switch off and disconnect from the mains Disconnect your test setup 6 1 2 Anode current meter calibration M2 This procedure requires an external floating power supply capable of delivering typically 0 5 1 5 ampere e g a mains supply or a small lead acid battery 1 Connect your anode current meter to the A and A terminals observe correct polarity Turn RV1 fully clockwise HV MINUS DMM 0 1 999A Floating 12V 100 ohms 2W power Supply or batttery Set full scale anode current CHASSIS GROUND Figure 10 Calibration setup for anode current meter Alternatively you can use a variable voltage current power supply 2 Connect a 1009 2W variable resistor to the positive terminal of your power supply and in series with this connect an accurate current meter to the A terminal see Figure 10 above Connect the negative terminal of your power supply to the HV MINUS terminal This will allow you to pass a known current through the anode meter shunt R2 and also the anode current trip resistor R3 see Section B 3 3 later 3 Apply power and adjust the current to a known value Then adjust RV1 to give the same reading on your meter scale 4 This completes the calibratio
23. cross R1 needs to be about 0 8V Therefore the over current protection for the meter M1 requires two silicon diodes in series D3 and D4 to prevent incorrect grid current reading when the meter is close to full scale A voltage proportional to the grid current is sampled by RV3 and generates base current into Q6 page B1 This causes collector current to flow through R13 which pulls pin 4 of USB down from the 12V line At a level of grid current set by RV3 this will trigger the flip flop U5A U5B which disables the PTT releases the TX TX relay K1 lights the red GRID HV alarm LED and turns off the green READY LED The GRID HV alarm is automatically reset when you release the PTT button or when the transceiver s VOX delay times out This will allow you to resume operating if the high grid current was only intermittent If the grid current is still high when you attempt to transmit again the circuit will trigger again to protect the tube Low HV Sensing The HV OK input measures a divided down sample from the anode high voltage rail The HV divider is separate from the Triode Board for general safety reasons See Section B 5Jand page PY for construction details At normal levels of HV the divider should be designed to give a sample voltage in the range 8 12V at the HV OK input If the HV is low so that the sample voltage falls below about 6V it will trigger the flip flop U5A U5B page B1 This disables the PTT releases We
24. ent Figure 3a uses a meter with a low resistance shunt while Figure 3b measures the voltage drop across a higher value metering resistor Triode Board AN 2 7 Issue 1 5 for board v2 4 January 2003 1999 2003 IFWtech Limited 500mA 500mA DZ 1 0 ohm S ZV L PROTECTION DIODE operates at 0 6V LOW VALUE Small voltage 0 5V SHUNT drop Figure 3 Two ways to measure 500mA anode current a Low resistance shunt a protection diode would be useless b 0 5V metering resistor with protection diode and adjustable range Problems with the low resistance shunt method Figure 3a x 1 The shunt resistor depends on the full scale reading required and also on the internal resistance of the meter x 2 The shunt resistor is always an unusual low value and it needs to be hand made from resistance wire 3 Itis difficult to adjust the value of the shunt to make the meter read correctly x 4 Protection diodes are ineffective with low resistance meters and shunts because the voltage drop is usually too low The diodes do not begin to operate until tnere is enough current to develop 0 6V which may be enough to destroy the meter The Triode Board uses the circuit of Figure 3b which overcomes all four of these objections v 5 The shunt resistor depends only on the full scale reading required v 6 Standard fixed resistor values can be used v 7 The trimpot allows you to adjust the full scale reading precisely
25. ent using a separate resistor R3 The voltage drop across R3 makes current flow through the opto coupler U1A This causes an approximately equal current to flow through U1B RV5 and R24 and this controls the voltage the voltage on pin 13 of USG If the anode current increases above a certain value it triggers the flip flop U5C U4A RV5 determines the level of anode current at which this happens When the flip flop is triggered pin 10 of USC goes high Q4 is cut off and the HV CTRL line goes low If this line is connected to a mains contactor in the primary of the HV transformer as shown on page 2B then it will switch off the HV within a few milliseconds and light the red ANODE alarm LED To reset the flip flop press the RESET button and allow the HV to come up again If the problem that caused the arc has cleared and no fuses have blown in the HV supply you can continue operating immediately Grid Current Protection Excessive Grid Current Excessive grid current can damage triodes very guickly It can be caused by any combination of high RF drive incorrect loading and or low HV The Triode Board monitors for high grid current and also for low HV If either condition is detected the PTT is disabled and the GRID HV alarm LED lights Grid Current Sensing See the schematics on pages 30Jand 31 Grid current is detected across R1 page Bo In order to operate the sensing circuit details below the maximum voltage drop a
26. er for the relay supply to the two AC IN terminals Apply mains power to the transformer WARNING Do not apply 115 230V AC mains directly to the Triode Board If you are using the normal 12V relay option the transformer should be 15V AC Check that about 20V appears at the UNREG terminal and that 12V DC appears at the output of U6 marked 12V under the board If you are using the 24V relay option the transformer should be 20V AC Check that about 28V appears at the UNREG terminal and that 12V DC appears at the output of U6 marked 12V under the board on the U6 side of where you cut the track 3 Switch off and disconnect from the mains Fix any problems with the 12 24V DC supply before you go any further 6 1 Meters 6 1 1 Grid current meter calibration M1 1 Connect your grid current meter to the G and G terminals observe correct polarity Turn RV2 fully clockwise 2 Connect a 1000 2W variable resistor to an external 12V DC supply and in series with this connect an accurate current meter to the A terminal see Figure 9 next page This will allow you to pass a known current through the grid meter shunt R1 Alternatively you can use a variable voltage current power supply Triode Board AN 2 19 Issue 1 5 for board v2 4 January 2003 1999 2003 IFWtech Limited DMM 0 1 999A 100 ohms 2W Set full scale grid current CHASSIS GROUND Figure 9 Calibration setup for grid current meter Altern
27. ic Checkout 1 Connect a 47kQ resistor in parallel with R21 under the board This will shorten the warm up time delay during testing Ignore this step if you have already configured R21 and C18 for a short delay 2 If you are using the PTT line in its standard ground to T X configuration ignore this instruction completely If you have modified the PTT switching for 12V TX then ground the PTT terminal now and reverse all future instructions to ground and un ground it 3 Insert all socketed ICs observe correct orientation and connect the LED board and RESET switch 4 Apply AC power from the transformer to the two AC IN terminals The red ANODE and GRID HV LEDs should both come on After about 5 seconds the ANODE LED should go out when the warm up timer completes Triode Board AN 2 21 Issue 1 5 for board v2 4 January 2003 1999 2003 IFWtech Limited Connect the UNREG terminal to HV OK to simulate a signal from the HV divider The GRID HV LED should go out and the READY LED should come on The HV CTRL terminal should be at almost 12V or about 24V if you chose the 24V relay option Ground the PTT terminal The TX LED should come on and you should hear the relay K1 operate Check for correct operation as you un ground and ground the PTT terminal While the PTT terminal is grounded disconnect HV OK from UNREG to simulate a low HV fault The TX and READY LEDs should both go out K1 should release and the GRID
28. idling current exactly as the manufacturer recommends The circuit is taken from the data sheet for the industry standard TL431 adjustable zener U2 An inexpensive Darlington power transistor Q1 handles the power dissipation and is rated to survive major current surges The Varistor VDR1 V24ZA50 provides further circuit protection The Triode Board cathode bias circuit is normally adjustable in the range from 3 to 27V which suits most tubes including the 3 500Z 3CX800 and 8877 For tubes such as the GS35b and GS31b which can require up to 30V bias or more at high anode voltages cut the thin track under the resistor marked HI B and insert a 1 5kQ resistor Change VDR1 to two V24ZA50 in series The component kit contains two V24ZA50 VDRs For the high bias option connect these in series on the board For the normal bias range use one VDR on the board and install the second VDR in the RF deck between the cathode DC connection and chassis ground For even higher bias see Application Note 5 at the rear of this manual 3 5 TX RX Switching TX RX changeover of the Triode Board is controlled via the PTT line which switches the bias relay K1 You will also need to control the coaxial changeover relays probably one at the input of the amplifier as well as one at the output You will also need to control the coaxial changeover relays probably one at the input of the amplifier as well as one at the output Spare changeover contac
29. ing coil meter recommended See Section h 2 tor details of meter selection and recommended scaling 6 M2 anode current 0 100uA moving coil meter recommended See Section k 2 for details of meter selection and recommended scaling 7 Transformer for 12V relays use 15V AC at up to 1A for 24V relays use 20V AC at up to 1A This transformer winding must not be connected to the transformer winding for the tube heater 8 HV divider to provide a 12 15V HV present signal and also act as a backup bleeder chain See Section Bs for details of construction You will also need a few temporary components and a multimeter for the setting up procedures 2 3 Choosing Configuration Options Every power amplifier is different so there are many possible options for cathode bias voltages metering etc Sections Band give full details Triode Board AN 2 5 Issue 1 5 for board v2 4 January 2003 1999 2003 IFWtech Limited 3 Triode Amplifier Control and Protection Please don t start to build the Triode Board until you have read all of Sections 3 5 The Triode Board is designed only for grounded grid triode RF power amplifiers Direct grounding of the grid to the chassis is mandatory in amplifiers above 30MHZ and it is the most common option for HF amplifiers also The Triode Board will function with HF amplifiers that have the grid raised above chassis ground but this feature must not be used for grid current metering 3 1
30. itional flexible wires to connect the RESET switch Figure 7 shows an example of a front panel layout and labels for the LED indicators From the top the LED colors should be TX green or blue READY green GRID HV and ANODE both red O TX O READY O GRID HV ae WARMUP RESET ANODE Figure 7 A front panel layout for the LED array and RESET button 5 5 Building the HV Divider The HV divider should be close to the RF deck so that the divider sees the same high voltage that the triode sees It should be designed to produce 8 12V at the HV OK input to the Triode Board The GRID HV alarm will trigger if the voltage at the HV OK input drops below about 6V The 1MQ resistors should be 0 5W metal film or metal glaze components each rated to withstand at least 350V To avoid voltage breakdown use at least four 1MQ resistors per kilovolt of HV off load HV No of resistors HV No of resistors 2000V 8 3000V 12 2500V 10 3500V 14 and so on The schematic of the HV divider is shown in Figure 8 and also in the Interconnections diagram on page 29 R106A Z R107 R108 It makes no sense to put the HV divider in a separate HV power supply because it will indicate HV OK even when the HV feed to the tube is totally disconnected Triode Board AN 2 17 Issue 1 5 for board v2 4 January 2003 1999 2003 IFWtech Limited HV ALL RESISTORS 1M 0 5W 350V to HVOK 100K 1W 100K 1W Two independent chassis g
31. n of the anode current meter Switch off power Disconnect your test setup Triode Board AN 2 20 Issue 1 5 for board v2 4 January 2003 1999 2003 IFWtech Limited 6 2 Cathode Bias Adjustment 1 Connect A1 observe correct connections To apply current through the cathode bias regulator connect a 470 1W resistor from the terminal of an external power supply to the E terminal of Q1 see Figure 11 Connect the terminal of the power supply to the C terminal of Q1 2 Connect an accurate voltmeter between the C and E terminals of Q1 as shown in Figure 11 Power supply 47 ohms 1W see text Figure 11 Cathode bias test setup 3 The voltage available from the power supply must be greater than the required bias voltage Apply power and check that RV4 will continuously adjust the bias voltage across the desired range Set RV4 to the approximate bias voltage for the tube you intend to use If you have a variable voltage current supply check that the cathode bias regulator will hold the regulated voltage constant over a current range from about 50mA up to at least 2A If you see even a very small variation it will probably be due to voltage drops in the interconnecting leads not the voltage regulator itself 4 Switch off and disconnect from the mains Disconnect your test setup This completes the meter calibration and checkout of the cathode bias circuit 6 3 Control Logic and Alarm Settings 6 3 1 Control Log
32. on in Section B 6 This control voltage is only available after the warm up timer has completed so no HV is applied during the warm up period If the anode current protection circuit triggers for any reason the HV control voltage is removed in less than 5 milliseconds HV control is an important safety feature We strongly recommend that you use it To use this feature you must install a 12V or 24V DC operated relay K101 to interrupt the mains supply to the HV transformer Make sure that the relay is capable of interrupting the maximum overload current of the transformer with a very large safety margin An electric motor relay or contactor is a good choice The Omron G7L 1A T SPNO 30A relay has proved very effective and is available in both 12V DC and 24V DC versions from many European and US suppliers There are also many other 24V high current relays and contactors 7 1 2 Step Start Circuit A step start circuit is strongly recommended and the Interconnections 1 diagram on aje Phlehow a circuit suitable for 220 240V mains 7 1 3 Blower Control To prolong tube life vou should allow plenty of time for the tube to cool down after transmitting The Interconnections 1 diagram on page PB shows a method to allow the blower to continue for a few minutes after the mains power has been switched off SW102 is athermal switch that is cemented on to the side of R101 which is connected across the 220 240V mains feed to the heater
33. onents left over Assemble the components to the board Observe polarity of diodes IC sockets and ICs Use a fine tip soldering iron watch out for missed pads and solder bridges Take care not to flood empty plated through holes with solder it can be difficult to remove Connections for all alarm LEDs and the RESET button are brought out to an 8 way header You may fit a standard 0 1in pitch connector not supplied with the kit or simply solder in wires When you have finished all wiring remove flux residues solder balls etc from both sides of the finished board Use denatured alcohol or isopropyl alcohol and an old toothbrush to clean the board Rinse well and allow to dry Check the board very carefully for incorrect components missed connections dry joints or solder bridges Use a magnifier Triode Board AN 2 16 Issue 1 5 for board v2 4 January 2003 1999 2003 IFWtech Limited 5 4 Building the LED Array The layout for the array of LED indicators and the RESET switch will depend on your individual front panel design A good way to build the LED array is to use 0 1in stripboard Veroboard etc Mount the LEDs on the stripboard and also use a scrap piece of board as a drilling template for the front panel If you have used an 8 way ribbon cable to connect to the Triode Board terminate the cable on to 8 copper strips wire 3 is unused Then connect the strips to your desired layout of LEDs using wire links Use two add
34. or even stronger In the connection pads for Q1 you can fit either blade terminals provided or use a three way 0 2in pitch connector not supplied with kit 2 Identify the components see below COMPONENT MARKINGS Check the markings on each component BEFORE you solder it in place make that a DOUBLE check Resistors Some resistors are marked with the familiar three band value code e g 10KQ is brown black orange BUT many resistors in the kit may be marked with a four band value code 1st digit 2nd digit ard digit always black number of zeroes In this coding a 10KQ resistor is brown black black RED so take care If in doubt measure the resistors with a multimeter The upright 5W resistors are marked with the European value codes e g 3R3 means 3 3Q OR56 means 0 569 etc Triode Board AN 2 15 Issue 1 5 for board v2 4 January 2003 1999 2003 IFWtech Limited Trimpots These may have a two digit marking 1st digit is value 2nd is number of zeroes 5002 52 1KQ 13 10KQ 14 Ceramic capacitors The 1nF capacitors are marked 102 read the code as 1 0 and 2 more zeroes i e 1 000pF or 1nF Similarly the 10nF capacitors are marked 103 and 0 1uF 100nF capacitors are marked 104 Diodes The small glass diodes are all 1N4148s All other diodes have their part number clearly marked Various alternatives may be supplied for the larger diodes and BR1 Transistors and ICs Note the
35. or values means Q e g 15R 159 3K3 3 3kQ 1M0 1 0MQ etc For better readability the multiplier letter replaces the decimal point so 0R33 0 330 1KO 1 0kQ etc The same applies to small capacitors e g 4n7 4 7nF nanofarads 4 700pF Triode Board AN 2 2 Issue 1 5 for board v2 4 January 2003 1999 2003 IFWtech Limited CONTENTS Ps E E A cence Seve EEE bo ap Roo etna aa Pooh uo B3 Appendix 1 Higher Cathode Bias assreraravnsnnrnrnvnenensvsrnrnvnvnenenenersrnrnrnnnnnnn Triode Board AN 2 3 Issue 1 5 for board v2 4 January 2003 1999 2003 IFWtech Limited 1 Features All on one PC board simplifies external wiring Cathode bias supply adjustable 3 30V precision regulated up to 2 5A or more Grid and anode current metering with meter protection Status output to four LEDS Relay TX RX switching Warm up timer also controls High Voltage Grid current and HV monitored protects sensitive grids from overdrive Anode current monitored for surge protection also controls your High Voltage supply 12 24V DC supply for external relays uses external mains transformer Highest RFI immunity high level CMOS logic extensive RF filtering and groundplane shielding Quality double sided PC board measures 5 7in x 3 3in Designed for key down forever reliability Triode Board AN 2 4 Issue 1 5 for board v2 4 January 2003 1999 20
36. orrectly It always looks good to use matched meters on your front panel and this universal calibration method allows you to use an identical matched pair even though they are measuring very different currents There are two basic requirements for meters 1 The full scale deflection current should be substantially lower than the current you are measuring 2 The full scale voltage drop inside the meter must be less than 0 5V The table below shows the maximum allowable internal resistance of the meter measure with a multimeter The preset variable resistors RV1 and RV2 are used to adjust the meters to exactly the correct full scale reading as described later in Section B The best value depends on the meter sensitivity choose from the table below Meter full scale Max internal RV1 RV2 O resistance 100uA 5k 5k 10k or 5k 1mA 500 500 1k or 500 10mA 50 50 100 The kit is supplied with two 5000 trimpots and two 5kQ trimpots so you should use the table to make the best choices for RV1 and RV2 you will have two trimpots left over 4 2 1 Example You have a pair of 0 1mA meters that you d like to use with the Triode Board 1 Check the internal resistance with a multimeter Le s say the value is about 400Q This is less than the limit of 5009 for a 1mA meter in the table above so these meters are OK to use 2 RV1 can be a 5000 trimpot the value supplied with the kit 3 RV2 can be a 1kQ trimpot but a 5
37. r face using a CAD package and glue the printout on to the existing scale plate This is a lot more effort but the results look very professional Figure 6 95 1 0 Figure 6 A meter scale re drawn using AutoSketch See http mywebpages comcast net tonne for WB6BLD s excellent free program that designs the scale for you Triode Board AN 2 14 Issue 1 5 for board v2 4 January 2003 1999 2003 IFWtech Limited 5 Building the Triode Board alle Please don t start to build the Triode Board until you have read all of Sections 5 1 Mounting the Board Use the bare PC board as a template to mark the chassis fixing holes hole centers 5 2in x 2 8in Fix the board to the chassis on 0 5 in 12mm pillars Metal pillars are only necessary as an extra RFI precaution see Section 7 4 If you use metal pillars take care to avoid shorting to the tracks beneath the board 5 2 Board Modifications If you wish to use the 24V relay option Section or to make the 12V PTT modification Section cut and link the necessary tracks on the board now before assembling any components 5 3 Assembling the Board 1 Fitthe blade connector tags to the board first Support the board on a firm flat sheet of expanded polystyrene Hold each tag with long nosed pliers and tap it gently into place with a very small hammer Solder to the PC pad let some solder run through the plated through hole to the top side to make the anch
38. rounds Figure 8 HV divider circuit Triode Board AN 2 The two 100kQ 1W resistors are selected to provide about 8 12V at the HV OK input to the Triode Board under normal operating conditions if you have used the correct number of 1MQ resistors for the off load operating voltage Note the two 100kQ resistors are safety components designed to make sure that there is no possibility of the chassis ground return failing because that would let HV into the low voltage circuit To make doubly sure use two completely independent high quality chassis ground connections Build the resistor chain on un clad fibreglass PC board close to the RF deck and provide good insulation for the high voltages involved The HV OK output from the divider is also a good point to connect a voltmeter which is calibrated to measure the high voltage If you are doing this the voltage at the HV OK output must be less than 12V otherwise the HV meter will read incorrectly due to the protection diode D6 Issue 1 5 for board v2 4 January 2003 1999 2003 IFWtech Limited 6 Off line Testing WARNING Follow the instructions in this section and test all the functions of the Triode Board BEFORE you install it in the amplifier It s much simpler and safer to do it this way 1 Remove any socketed ICs Disconnect Q1 Disconnect the feed from the HV divider to HV OK Disconnect the LED indicator board 2 Connect the mains transform
39. s and HV R101 is intended to run hot and SW102 will close when its temperature reaches 60 C which happens after a few minutes of normal operation When you switch off the amplifier using SW101 the thermal switch SW102 remains closed until it cools down and thus keeps the blower running for a few minutes more Thanks to GW3NWS for this idea Triode Board AN 2 24 Issue 1 5 for board v2 4 January 2003 1999 2003 IFWtech Limited 72 HV Control and Safety 7 2 1 HV Mains Control See Section 7 2 2 HvV minus Rail For additional safety the HV minus rail should be connected to chassis ground by a large reliable 1kQ resistor close to the bottom of the capacitor stack This resistor is shown as R105 in the Interconnections 2 diagram on page 29 Note if R105 is less than 2000 11 will affect the accuracy of the anode current meter The Triode Board already provides safety diodes for the HV minus rail Do not connect any additional safety diodes between the HV minus rail and chassis they are not necessary and also they may prevent the meters from reading correctly 7 2 3 Safety Resistor in the HV Rail This resistor is R104 in the Interconnections 2 diagram on page 29 It limits the maximum possible anode current in any sudden surge condition Eimac recommends limiting the maximum possible surge current to 40A or less for transmitting tube up to about 1500W anode dissipation This implies that the resistor should be about
40. t be quite correct Use RV4 to adjust the zero signal cathode current to the manufacturer s recommended value 4 Release the PTT This completes the cathode bias adjustment 8 3 RF Testing RF testing of power amplifiers is outside the scope of this Application Note but whichever way you do it the Triode Board will protect the tube s Triode Board AN 2 26 Issue 1 5 for board v2 4 January 2003 1999 2003 IFWtech Limited 9 Updates and Product Support Updates and further Application Notes will be provided on the World Wide Web and by e mail e G3SEK http www ifwtech co uk g3sek boards If you purchased the Triode Board from Tom s Tubes in the USA please e mail boardsQifwtech co uk to be included on the list for future e mail updates For advice on details not covered by these notes you can e mail G3SEK direct e boardsQifwtech co uk Triode Board AN 2 27 Issue 1 5 for board v2 4 January 2003 1999 2003 IFWtech Limited Triode Board Interconnections 1 HV CONTROL STEP START FS101 SW101 ON OFF 25A contacts K102 A L 25A contacts L A A HV SUPPLY 15A F K101A U a 0 BLOWER U HV U R102 FS104 i 47R 50W reg R103 220 240V AC LA 2K2 25W I U E Hv minus E cy V i NZ D101 _ I SW102 BLOWER DELAY 1N4007 N O lt 60degC I Cemented to R101 I R101 it B mn p 10K 9 11W Z NO A a I I C101 I 1000UF 35V I FS103 O HV CTRL 2AT A K101 p D102 12V DC ZN 1N
41. transistor outlines printed on the board these are correct for the devices supplied in the kit but they may not be correct if you make substitutions Observe static precautions when handling transistors Q1 is mounted separately on its own heatsink following the E C B connections printed on the board The pinout of 01 is shown in the schematic on page B Take care to install all the DIL sockets with the index notch in the correct positions U1 U4 and U5 up U3 down Heatsinks You must provide the large off board heatsink for Q1 as detailed in Chapter 2 or use the chassis You must also provide nuts and screws to fix the TO 220 transistor tabs to all of the heatsinks For Q1 there is a plastic bush to insulate the bolt from the transistor tab and also a special insulating heat conducting washer Do not use heatsink compound with this washer but do make sure that the heatsink is flat with no burrs around the mounting hole For the small on board heatsink for U6 use heatsink compound with a nut and bolt No insulation is required Use the table on page 12 to identify which values of 5W resistors you will need for R1 R2 and R3 Also use the table on page f13 to identify which values of trimpots RV1 and RV2 you will need to suit your tube s and meters The kit includes a range of resistor and trimpot values to cover a wide range of possible tubes and meters When you have made your choices there will be some comp
42. ts List 6 Underneath the board cut the track marked 12V where it narrows and link across the gap marked 24V as shown below a Figure 4 Modifications for 24V relays underside view 18V 7 The 12V regulator U6 will not need a heatsink 3 7 PTT Options When the PTT line is grounded the current drawn from the transceiver is about 10uA When the PTT line is un grounded the open circuit voltage is regulated at 12V This is compatible with the PTT output of almost every known transceiver For transceivers that provide 12V output on transmit and a short to ground on receive follow these conversion instructions 1 On the underside of the board beneath U4 cut the thinned track between pin 4 and pin 11 Figure 5 2 Join the link between pins 6 and 12 by bridging the small gap at pin 12 Figure 5 Modifications U4 for 12V PTT lad ile ME underside view Link tracks here 3 Do not insert R15 1 po i R Na Gut track here Triode Board AN 2 11 Issue 1 5 for board v2 4 January 2003 1999 2003 IFWtech Limited 3 8 Warm up Timer Options The warm up timer is a standard 555 circuit page B1 The values of R21 and C18 shown give a time delay of about 3 minutes which is suitable for most indirectly heated cathodes For tubes such as the 3 500Z with a directly heated filament you should reduce the warm up delay to a few seconds e g by changing C18 to 10uF and R21 to 150 220kQ Note even with
43. ts on K1 can be wired as you need these are marked NC closed on RX NO open on RX and C common At this time the Triode Board does not provide sequenced TX RX changeover on board but it is compatible with external sequencers Many transceivers provide a few milliseconds delay between PTT operation and the start of RF output which may allow you to switch the coax relays safely from the spare contacts of K1 The Triode Board will support full break in changeover If you do not wish to use Low HV sensing connect the HV OK input permanently to the 12V DC output from the voltage regulator U6 The rest of these instructions assume that Low HV sensing is used Triode Board AN 2 10 Issue 1 5 for board v2 4 January 2003 1999 2003 IFWtech Limited QSK if you replace K1 with an electronic bias switch and provide the necessary sequenced timing 3 6 24V Relay Option The Triode Board includes its own rectifier and voltage regulator for the 12V DC rail If you are using 12V DC relays use the Triode Board as supplied with a transformer input of 15V AC to the two AC IN terminals If you are using 24V DC relays you will need to make the following simple changes 1 Change the transformer to 20V AC Change R28 to 10K Change R27 to a 15V 0 25 0 5W zener e g BZX79 C15 or 1N4109 etc with its cathode stripe nearest to Q4 4 Change R30 and R32 to 1K 1 2W Change K1 to RTE24024 Schrack or Potter amp Brumfield see Par
44. vides nut amp DK HS222 ND bolt 1 none 6 DIL socket U1 1 none 8 DIL socket U3 2 none 14 DIL socket U4 U5 25 none Connector blades 2 8mm 0 110in x 0 8mm F 347 2528 PCB 25 none Blade sockets 2 8mm 0 110in x 0 8mm F 362 5394 1 P1 J1 8 way 0 1in header For LEDs and SW1 optional and connector 1 none 3 way 0 2 in header For Q1 optional or use and connector blades Triode Board AN 2 36 Issue 1 5 for board v2 4 January 2003 1999 2003 IFWtech Limited Appendix 1 THE TRIODE BOARD Control and Protection for your Triode RF Power Amplifier Application Note 5 Higher Cathode Bias This Application Note explains how to modify the existing bias circuit for the higher voltages required by the Russian GS31 and GS35 triodes Triode Board AN 2 37 Issue 1 5 for board v2 4 January 2003 1999 2003 IFWtech Limited Appendix 1 1 Original Bias Circuit As you know the Triode Board uses a true constant voltage bias regulator which is fully adjustable so you can set the idling current exactly as the manufacturer recommends The circuit is taken from the data sheet for the industry standard TL431 adjustable zener U2 Voltage regulation is within a few millivolts from idling currents of lt 50mA up to at least 2 5A An inexpensive Darlington power transistor Q1 handles the power dissipation and is rated to survive major current surges The Varistor VDR1provides further circuit protection
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