Dental X-Ray Units MD0361 - DelMarVa Survival Training Website
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1. After you have completed all of these items turn to Solutions to Exercises at the end of the lesson and check your answers with the solutions 1 How often must you calibrate verify the portable dental x ray unit a Daily b Weekly c Monthly d Annually 2 How often must you perform a power supply line adequacy test on the portable dental x ray unit a Before every use b Whenever reassembled c Whenever cleaned d Whenever the unit has lost power 3 When you calibrate the dvm you set the multimeter to which of the following vac a 50 b 100vac c 150vac d 250vac MD0361 2 11 4 When you calibrating the and the voltage reading does not match the reading on the multimeter which of the following procedures do you use If the external multimeter readings are higher than the unit s reading you should turn R7 counterclockwise b Ifthe external multimeter readings are lower than the unit s dvm reading you should turn R7 counterclockwise If the external multimeter readings do not match exactly replace the d If the external multimeter readings do not match you must replace your power source 5 You are verifying the exposure time Which of the following findings are acceptable a For 0 066 seconds at 50 Hz you have 5 pulses b For 0 066 seconds at 60 Hz you have 1 pulse C 3 2 seconds at 50 Hz you have 165 pulses d For3 2 seconds2. g Lay the scissors arm and X ray head on a flat surface MD0361 4 2 T7 Figure 4 1 Scissors assembly MD0361 4 3 2 Remove the cabling to the generator Refer to figure 4 2 and use the following steps a Loosen the safety strap 37 1 until you have opened the scissors arm 37 about 7 inches b Secure the safety strap with adhesive tape c Remove the cover cap 93 d Unscrew the cover 71 and cover cap 72 37 Scissor Arm 37 1 Safety Strap 38 Generator 71 Cover 127 1 72 93 Cover 95 Angle Support bracket 127 1 Scissors Arm Cabling Figure 4 2 Scissors arm cabling fitting part one MD0361 4 4 e Remove the scissors cabling 127 1 from the generator 38 by gently pulling the prongs of plug connections 3 4 5 and 6 from the generator f Unscrew the grounding screw on the arm to disconnect the grounding wire g Unscrew and remove the angle support bracket 95 h Pull out the Heliodent generator 38 3 Prepare to remove cabling from scissors arm number one Refer to figure 4 3 for the following steps a Unscrew the axle 21 4 screws and remove it from scissors arm b Remove the cable clip A 18 B 127 1 21 A 2 Cable Clip Bolt Connection Locking Ring Bolt Connection Sleeve Strain Relief Locking Screws Greenfield Tubing Multi pin Plug Axle Defective Cabli
3. and if the unit is on an automated system a report from either The Army Maintenance Management Information System TAMMIS or the Army Medical Department Property Accounting System AMEDDPAS 1 Check the performance history of the X ray for any recurrent problem Check DA Form 2404 Equipment Inspection and Maintenance Worksheet if available or the automated print out as necessary 2 Be alert for any systematic problems that you find during your review 3 If you are on a manual system non automated record all uncorrected conditions on DA Form 2404 as you perform PMCS 4 Fora manual system record the performance of PMCS on the following forms DD Form 314 Update after completing PMCS b DD Form 2164 X ray Verification Certification Worksheet Complete and attach a list of test equipment used during procedure c DA Form 2409 Update after completing PMCS d DD Form 2163 Medical Equipment Verification Certification Label Complete and attach to the unit b Complete a DA Form 2407 Maintenance Request and if applicable a DA Form 2406 Material Condition Status Report 5 if additional maintenance is required b Equipment To perform PMCS on a field dental X ray machine you need the following equipment 1 A digital multimeter with the following specifications a Alternating current ac voltage 0 5 of reading plus 1 digit b Direct current dc voltage 0 196 of reading plus 2 d
4. from the power source Accordingly the Heliodent is then operated from the line without damping 2 As soon as the capacitor is charged to the threshold voltage set the Schmitt trigger the timer circuit shuts the ER relays down and the exposure is terminated The AR relay drops only as the trigger switch is released MD0361 3 6 Exposure button Tube current pers aaa aa a 5 n 5 5 5 S S S N ES 5 ES 5 5 5 i i Ss WNW NS S PC board D3 S Digital voltmeter P 22 Relay b lt 1 Figure 3 7 Theory of principles of operation logic block diagram 3 7 3 You cannot measure the tube current between the points X and Y since an alternating current flows there tube current plus capacitor charging current Thus the diodes V2 and V3 have short circuited the capacitor charging current in the tube current measuring circuit You may measure the tube current between points D1 9 D1 10 Refer to figure 3 8 Figure 3 8 Heliodent 70 secondary circuit b Heliodent 70 The secondary circuit of the Heliodent 70 consists of a voltage doubling circuit C1 V10 H1 The negative half wave of the transformer voltage charges the capacitor C1 The positive half wav
5. a voltage drop on the resistor R3 which is greater than the following U V4 2 4v U V5 0 7v V6 0 7v the transistor V6 is controlled through Then the transistor V7 is also controlled through R9 The collector current of V7 allows the AR relay to draw This relay places the Heliodent 70 transformer under a voltage of 125 without damping 2 The collector current of V7 flows at the same time through V8 R8 R5 to the base of V6 and keeps V6 in the over modulated state flip flop function The capacitor C7 and C2 serve for interference suppression 3 The transistor V7 also controls the transistor V17 This transistor serves as an impedance converter and provides a supply voltage stabilized by V18 to the integrator consisting of R10 and C3 The exposure times of 0 066 and 3 2 seconds sec are set in 18 steps with R10 h End of Exposure As soon as C3 is charged to the threshold voltage which is adjusted with R13 the transistor V12 switches through This initiates a flip flop process On the one hand the transistor V12 short circuits the base section of V14 so that the current through ER is reduced On the other hand the voltage drop on R13 decreases so that the transistor V12 is controlled through even faster Thus the ER relays drop Refer to figure 3 10 i Temperature Compensation The R11 hot wire compensates the temperature response of the entire circuit in the 10 to 70 Celsius C range Refer to
6. at 60 Hz you have 171 pulses Check Your Answers on Next Page MD0361 2 12 SOLUTIONS EXERCISES LESSON 2 1 2 MD0361 d b para 2 1 para 2 3 para 2 4c para 2 49 1 figure 2 9 End of Lesson 2 2 13 LESSON ASSIGNMENT LESSON 3 Isolate Malfunctions to Module Level in the Inter oral Dental X ray TEXT ASSIGNMENT Paragraphs 3 1 through 3 7 LESSON OBJECTIVES After completing this lesson you should be able to 3 1 Identify the steps required to isolate malfunctions in the Inter oral Dental X ray to the module level 3 2 Identify the functioning of the Heliodent 70 Inter oral Dental X ray SUGGESTION After completing the assignment complete the exercises at the end of this lesson These exercises will help you to achieve the lesson objectives MD0361 3 1 LESSON 3 ISOLATE MALFUNCTIONS TO MODULE LEVEL IN THE INTER ORAL DENTAL X RAY 3 1 GENERAL This lesson covers the general procedures you will use to isolate malfunctions in the X ray inter oral dental to the module level This lesson also explains the X ray s theory of operation and some of the safety hazards resulting from defective X ray modules that preclude operation of the unit until you have made repairs 3 2 HELIODENT 70 MODULES This lesson further describes the modules discussed in Lesson 1 a Power Equipment Power equipment consists of circuit boards found in the X ray control the transformer and the protectiv
7. latches are not broken or missing b The pressure relief valve is operational that is the push button is not broken or missing and springs back after release c The case lid gasket does not have cuts or nicks d All straps are intact e The leveling devices are not broken or missing and are functional MD0361 1 7 2 Inspect the seat assembly to ensure the following conditions exist a The adjustable brackets are operational b The head rest adjusts throughout its range of motion c The dowel pins and chains are not broken or missing d The seat and the back rest are not splintered or broken 3 Inspect the scissors arm assembly spring adjustment Position the tube head in a 45 angle to the vertical scissors arm If the scissors arm does not return by itself to 452 the friction pad requires adjustment See figure 1 3 Use the following procedures to adjust the friction pad a Loosen the locking screws A for the spring arm adjustment screws in the pivoting arm by turning them 1 1 2 turns maximum b Remove the screw caps B from the double joint of the scissors arm See figure 1 4 c Adjust the spring with screw C if the angle is more than 45 See figures 1 4 1 5 and 1 6 d Adjust the spring with screw D if the angle is less than 452 See figures 1 4 1 5 and 1 6 e Tighten screw A by turning it 1 1 2 turns maximum See figure 1 3 MD0361 1 8 Figure 1 3 Rotation adjustment step
8. schedule to ensure compliance with the Federal Performance Standard Your failure to perform the manufacturer s recommended maintenance relieves the manufacturer and his agents from responsibility 1 2 PORTARAY COMPONENTS AND OPERATING CONCEPT The Portaray unit consists on a carrying case support stand scissors arm tube head assembly a control assembly and a patient chair with adjustable head rest The unit has an operating tube voltage of 70 kilovolt potential kvp and a tube current of 7ma The aluminum Al filtration in the useful beam is 2 7mm millimeters total You accomplish the exposure technique setting by matching the patient to the object on the dial corresponding to the object being radiographed You can operate the Portaray on an adequate power supply of 109 volts alternating current vac to 133vac at 60 Hertz Hz 109vac to 132vac at 50 Hz and when you connect it to the transformer built into the case at 207vac to 242vac at 60 Hz and 207vac to 240vac at 50 Hz See figure 1 1 MD0361 1 2 Scissor X ray head Head rest assembly Seat assembly Carrying case eveling brackets Figure 1 1 Portaray system and its major components MD0361 1 3 1 3 FORMS AND EQUIPMENT REQUIRED FOR PREVENTIVE MAINTENANCE CHECKS AND SERVICES a Forms Each time PMCS is scheduled on a dental X ray unit you will receive DD Form 314 Preventive Maintenance Schedule and Record DA Form 2409 Equipment Maintenance Log
9. to Lesson 1 paragraph 1 4b 4 a and b MD0361 3 17 3 6 ISOLATE PRINTED CIRCUIT BOARD MALFUNCTIONS a If there is no display on the digital voltmeter determine if the D3 pcb is malfunctioning b If the line compensation leds do not operate determine if the D5 pcb is malfunctioning 3 7 ISOLATE OTHER MALFUNCTIONS a If the power supply is not within the specified range of 109vac minimum to 133vac maximum the power supply requires replacement Refer to Lesson 1 paragraph 1 4b 7 a through g for test procedures b If the exposure time pulse count is not within tolerance see Lesson 2 paragraph 2 5 1 and 2 c If the dose levels are lower than specified the X ray head requires replacement To measure the dose follow these procedures Refer to figure 3 15 MDH X ray Monitor lon chamber 700 150 X ray head Barometric Pressure Threshold Exposure Rate Figure 3 15 Dose measurement MD0361 3 18 1 Setthe exposure time to 1 0 sec 2 Remove the lead cap from the collimator of the X ray head a Usethe MDH X ray monitor or equivalent to measure the dose b Position the X ray head to the ion chamber as shown in figure 3 15 90 same central plane For reproducibility a special holding device with a radiation barrier can be used 3 Make the following adjustments to the MDH X ray monitor Setthe THRESHOLD to 0 2 b Setto the proper BAROMETRIC PRESSURE c Setto EXPOSURE RA
10. 0 5 ARMY MEDICAL DEPARTMENT CENTER AND SCHOOL FORT SAM HOUSTON TEXAS 78234 6100 Vu 22 J 27 Te 34 2 2 I xs rd DENTAL X RAY UNITS SUBCOURSE MD0361 EDITION 100 DEVELOPMENT This subcourse is approved for resident and correspondence course instruction It reflects the current thought of the Academy of Health Sciences and conforms to printed Department of the Army doctrine as closely as currently possible Development and progress render such doctrine continuously subject to change ADMINISTRATION Students who desire credit hours for this correspondence subcourse must enroll in the subcourse Application for enrollment should be made at the Internet website http www atrrs army mil You can access the course catalog in the upper right corner Enter School Code 555 for medical correspondence courses Copy down the course number and title To apply for enrollment return to the main ATRRS screen and scroll down the right side for ATRRS Channels Click on SELF DEVELOPMENT to open the application then follow the on screen instructions For comments or questions regarding enrollment student records or examination shipments contact the Nonresident Instruction Branch at DSN 471 5877 commercial 210 221 5877 toll free 1 800 344 2380 fax 210 221 4012 or DSN 471 4012 e mail accp amedd army mil or write to NONRESIDENT INSTRUCTION BRANCH AMEDDC amp S ATTN MCCS HSN 2105 11TH STREET SU
11. 1 Figure 1 4 Rotation adjustment step 2 Figure 1 5 Rotation adjustment step 3 Figure 1 6 Rotation adjustment step 4 MD0361 1 9 4 Ifthe tube head drifts the brake is malfunctioning Adjust the brake with an open end wrench See figure 1 7 a Tighten the brake firmly but gently b Check the various arm positions for drifting Figure 1 7 Open end wrench 13mm 1 2 inch 5 Inspect the control and the tube for a burned light bulb 6 Inspect the hand control cable for cuts and nicks WARNING The power supply must be grounded MD0361 1 10 7 Verify the adequacy of the power supply NOTE Line voltage must be 109 to 133vac at 60 Hz or 109 to 132vac at 50 Hz If the line voltage is not within tolerance you must replace the voltage source a Remove the front cover by removing the two screws on the top and the two screws on the bottom of the front cover See figure 1 8 Remove screws to remove housing cover Loosen screws to remove cover 109 133 Housing cover Figure 1 8 Multimeter connections for power supply adequacy test MD0361 1 11 b Setthe multimeter selection to 150 c Connect the multimeter leads to terminals and d Turn the unit on and allow it to warm up for five minutes e Verify that the voltage on the multimeter coincides with the unit s dvm The measured line voltage must be at least 109vac and may not exceed 133vac NOTE Ift
12. 21 CFR Subchapter J applicable at date of manufacture applicable at date of manufacture Date of manufacture Date of manufacture wu MTT Siemens Akliengesellschaft Siemens Aktiengesellschafl Wittelsbacherplatz 2 D 8 M nchen 2 Wittelsbacherplatz 2 D 8 M nchen 2 Germany Germany R hre Tube SR 70 7 Madel No 11 54 269 V 1022 Serial No MADE IN GERMANY SIEMENS HELIODENT 70 58 37 241 X 1341 0 125 7m 60 Hz 2 7 mm Al MADE IN GERMANY iid 58 75 885 D3152 Serial 602 MADE GERMANY X ray head 125V 5060 2 14 7 5 HELIODENT 70 This product complies DHHS regulations 21 CFR Subchapter J WARNING applicable at date of manufacture TO PREVENT FIRE OR SHOCK Date of manufacture HAZARD DO NOT EXPOSE THIS APPLIANCE TO RAIN OR Siemens Aktiengesellschaft MOISTURE Witlelsbacherplatz 2 D 8 M nchen 2 Germany CAUTION LIVE PARTS DISCONNECT FROM SUPPLY BEFORE OPENING ACHTUNG VOR OFFNEN SIEMENS DENTOTIME Netzspannung abschalten FEE X Ray Equipment pt 4666 Classified by 2 5 2 f Underwriters Laboratories Inc 6 with Respect to Electrical Fire Shock and Mechanical Hazards Only 245 B TO THF RFQUIRFMFNTS THF CANADIAN FI FCTRICAI CONF CSA HAS NOT INVESTIGATED OTHER PHYSIOLOGICAL EFFECTS CERTIFIE SELON LES EXIGENCES DU CODE CANANDIEN DE L E
13. IATION Exposure time setting in seconds Equivalent Accuracy of time setting in pulses pulses 60 HZ 50HZ 0 066 4 3 41 2 0 083 5 4 41 2 0 10 6 5 41 2 0 13 8 6 41 2 0 16 10 8 41 2 0 20 12 10 41 2 0 25 15 12 41 2 0 32 19 16 41 2 0 40 24 20 41 2 0 50 30 25 41 2 0 64 38 32 2 4 0 80 48 40 2 4 1 0 60 50 3 6 1 2 72 60 3 6 1 6 96 80 5 10 2 0 120 100 6 12 2 5 150 125 7 14 3 2 192 160 10 20 Figure 2 5 Exposure time performance parameters 2 3 VERIFYING ADEQUACY OF THE POWER SUPPLY Since the portable x ray unit requires assembly and disassembly as it is transported from location to location you must perform a power supply line adequacy test every time you reassemble the unit for use You must document the performance of the power supply line adequacy test on the Test Record in accordance with local standard operating procedures You perform this task as part of scheduled quarterly PMCS The specific procedures are described in Lesson 1 Perform PMCS on the Inter oral Dental X ray 2 4 CALIBRATE THE DIGITAL VOLTMETER To calibrate the digital voltmeter use the following procedures a Turn the unit off b Remove the screws from the housing cover and remove the cover c Set the multimeter to 150vac MD0361 2 5 d Connect the multimeter test leads to terminals N and L printed circuit board pcb D3 See figure 2 6 Remove screws to remove housing cover Loosen screws
14. ITE 4191 FORT SAM HOUSTON TX 78234 5064 Be sure your social security number is on all correspondence sent to the Academy of Health Sciences CLARIFICATION OF TERMINOLOGY When used this publication words such as him his and men are intended to include both the masculine and feminine genders unless specifically stated otherwise or when obvious in context USE OF PROPRIETARY NAMES The initial letters of the names of some products may be capitalized in this subcourse Such names are proprietary names that is brand names or trademarks Proprietary names have been used in this subcourse only to make it a more effective learning aid The use of any name proprietary or otherwise should not be interpreted as endorsement deprecation or criticism of a product nor should such use be considered to interpret the validity of proprietary rights in a name whether it is registered or not Lesson MD0361 TABLE OF CONTENTS INTRODUCTION PERFORM PREVENTIVE MAINTENANCE CHECKS AND SERVICES ON THE INTER ORAL DENTAL X RAY Exercises PERFORM VERIFICATION CALIBRATION OF THE INTER ORAL DENTAL X RAY 4 22 Exercises ISOLATE MALFUNCTIONS TO MODULE LEVEL IN THE INTER ORAL DENTAL X RAY eee Exercises REMOVE AND REPLACE OR REPAIR DEFECTIVE MODULES IN THE INTER ORAL DENTAL X RAY Exercises Paragraphs CORRESPONDENCE COURSE OF THE U S ARMY
15. LECRTICITE L X ray control ACNOR PAS ETUDIE LES AUTRES EFFETS PHYSIOLOGIQUES POSSIBLES DENTOTIM E Figure 1 2 Product label placement MD0361 1 6 2 Verify that the line compensation light emitting diode led yellow green red lights up the digital line adequacy voltmeter 3 Check the radiation warning light and the acoustic buzzer for proper functioning 4 Make sure that the deadman feature interrupts the X ray exposure after releasing the exposure switch If the X ray exposure is not interrupted perform the following procedures a Test the deadman feature as described in Lesson 3 paragraph 3 4a 1 a e b Calibrate the exposure time per procedures in Lesson 2 paragraph 2 5a f 5 Calibrate the unit See Lesson 2 Perform Verification Calibration of the Inter oral Dental X ray 6 Exchange the desiccant bag 18 months after date of manufacture and then every year The desiccant bag is in the storage packaging and has a color indicator blue means good pink means not good b Quarterly PREVENTIVE MAINTENANCE CHECKS AND SERVICES When you receive DD Form 314 on a dental X ray unit for scheduled PMCS you perform the PMCS To perform PMCS on a field dental X ray machine you need the following equipment the multimeter and pulse counter designated in paragraph 1 3 above Use the following procedures 1 Inspect the carrying case to ensure the following conditions exist a The carrying handles and
16. MEDICAL DEPARTMENT CENTER AND SCHOOL SUBCOURSE MD0361 DENTAL X RAY UNITS INTRODUCTION The seven milliampere ma Portaray Heliodent is a portable field dental X ray apparatus suitable for use in intra oral radiology The Portaray can be operated on an adequate power supply at 50 Hertz cycles per second Hz or 60 Hz When connected to the transformer built into the case it can also be operated on heavier power supplies It is your job to keep it operationally efficient The material in this subcourse provides the preventive maintenance checks and services PMCS verification calibration malfunction isolation and removal and replacement procedures you use to accomplish this task Subcourse Components This subcourse consists of 4 lessons as follows Lesson 1 Perform Preventive Maintenance Checks and Services on the Inter oral Dental X ray gt Lesson 2 Perform Verification Calibration of the Inter oral Dental X ray gt Lesson Isolate Malfunctions to Module Level in the Inter oral Dental X ray Lesson 4 Remove and Replace Defective Modules in the Inter oral Dental X ray Credit Awarded Upon successful completion of the examination for this subcourse you will be awarded 5 credit hours To receive credit hours you must be officially enrolled and complete an examination furnished by the Nonresident Instruction Branch at Fort Sam Houston Texas You can enroll by going to the web site http atrrs army mil and enrol
17. Metal film resistor 12 R10 R11 812 R4 13 C4 T1 14 1 C5 R17 R16 3 4 ISOLATE TROUBLESHOOTING ALERT MALFUNCTIONS a If the radiation visible and audible indicators do not stop when you are testing the deadman feature you can isolate the fault to a maladjusted or malfunctioning Dentotime pcb D1 1 The deadman feature permits the premature immediate termination of X rays To test this feature you use the following procedure a Setthe object exposure time selector to 3 2 seconds b Cover the collimator with a leaded cover cap c Move at least 6 feet from the X ray head to avoid exposure to X rays d Make an exposure with the exposure button Count 5001 five thousand one which equals approximately one second Release the exposure button the audible and visible radiation indicators must terminate immediately e Disconnect the unit from the power supply immediately in the event the radiation visible and audible indicators do not stop 2 Remove and replace the Dentotime pcb D1 and adjust it per procedures in Lesson 2 paragraph 2 5 before returning the device to service b If the audible signal and red radiation emission light come on together but the exposure time is noticeably longer than the time selected the problem is caused by either a timer malfunction defective scissors arm wiring or a defective X ray head 1 To determine if the malfunction is due to an incorrect exposur
18. NSE NOE a 93 S4 lt 8 22 95 2 8 2 09 05 60 Figure 2 7 Pcb D3 2 8 MD0361 014 01 21 6 Test point Pulse counter Figure 2 8 Mechanical counter test points c Turn the unit on and allow a 5 minute warm up period d Set the exposure time as shown in figure 2 9 and make an exposure Note the pulses on the counter PULSES Exposure 50 HZ 60 HZ Tolerance 0 066 sec 3 4 1 pulses 3 2 sec 160 192 10 pulses 20 pulses Figure 2 9 Exposure time tolerances MD0361 2 9 e Record the pulses the monitor f If not within tolerance adjust the pulse count before proceeding To adjust the pulse count use the following procedures 1 Make an exposure 2 Adjust the pulse using potentiometer R13 on circuit board D1 until the proper pulse count is obtained Refer to figure 2 10 a Increase the exposure time 0 Decrease the exposure time Figure 2 10 Pulse count adjustment CAUTION Observe the cooling time between exposures See the cooling chart in the manufacturer s service manual to determine the correct cooling period for a relative power duration Continue with Exercises MD0361 2 10 EXERCISES LESSON 2 INSTRUCTIONS Answer the following items by completing the statement or by writing the answer in the space provided at the end of the item
19. TE d Setto MEASURE 4 Make an exposure a The measured dose should be 700 millirads mr plus or minus 150mr b For reproduceability note the distance D where the measured dose value is obtained 5 Ifthe dose levels are lower than specified above you need to replace the X ray head d If no X rays are emitted from tube head but all visual and audible indicators are functioning the X ray head is defective 1 To verify that the X ray head is defective use a fluorescent screen a Place the fluorescent screen on a table or counter top as shown in figure 3 16 b Place a coat over the X ray head in order to dim the surrounding area c Set exposure time 1 0 sec d Make an exposure Refer to figure 3 17 MD0361 3 19 Fluorescent screen Figure 3 16 No X rays emitted from Figure 3 17 Exposure to test for blank tube head radiographs 1 Atthe same time the red radiation indication lamp at the Dentotime will light up and you will hear the alert sound 2 During the exposure the radiation will be visible on the fluorescent screen 3 If the fluorescent screen does not show the radiation effects the X ray head is defective even though the lamp lights up and the alarm sounds e If no X rays are present make the second test for electrical measurement See figure 3 18 MD0361 3 20 Range 150vac Figure 3 18 Electrical measurement 2 To test electrical measurement us
20. a reading on the multimeter NOTE Thereading should be 7ma with a tolerance of 1 2ma to 2ma at 60 Hz or 1 0ma to 2 5ma at 50 Hz If the tolerance is exceeded you must replace repair circuit board D1 i Replace the cover on the control 9 Inspect the tube head from stop to stop If the tube head turns more than 540 1 1 2 turns you must replace the rotational part See Lesson 4 Remove and Replace or Repair defective modules in the Inter oral Dental X ray 10 Correct minor deficiencies 11 Record the deficiencies not corrected on DA Form 2404 and complete the appropriate reports and forms c Weekly Preventive Maintenance Checks and Services Within one week of previous weekly maintenance or if equipment is dusty or dirty wipe all equipment surfaces with a damp lint free cloth d Daily Preventive Maintenance Checks and Services You must conduct visual checks and tests before the unit is operated 1 Verify that all labels are affixed and legible See figure 1 2 2 Look for mechanical damage possibly affecting radiation safety 3 Inspect components for rust cracks wear fraying electrical cords missing parts and operator s publication 4 the tube head in all working positions for possible drift MD0361 1 14 5 Look at the operating ready light green led line compensation indicators leds and the digital line adequacy voltmeter The operating ready light must light up and the must be func
21. arts 74 75 77 76 as shown in figure 4 10 78 Replace parts as needed 76 Figure 4 9 X ray head removal part two Figure 4 10 X ray head removal part three MD0361 4 14 screw NOTE Reassemble Parts in Reverse Sequence Refer to figure 4 11 Take care not to pinch electrical wires 1 Grease the bracket 22 2 Secure the shaft with the bracket 22 to the arm using the countersunk 3 Install the brown cover over the joint 23 it snaps into place 4 Test the tube head rotation from stop to stop from 540 1 1 2 turns Rotation beyond 1 1 2 turns indicates improper assembly Wiring damage will occur if not corrected 5 Connect the five wires of the X ray tube assembly to the wires of the scissors arm according to the markings Refer to figure 4 12 and the chart below X ray tube assembly wires 3 4 5 Scissors arm wires 3 4 5 6 6 MD0361 5400 Figure 4 11 X ray head reassembly part one 4 15 6 Ground connections 7 Connect and secure the leads as shown in figure 4 13 8 Press in the U channel 9 Place the cap on the yoke taking care not to pinch electrical wires 10 Place the cover over yoke and fasten with screw U channel Cap Figure 4 12 X ray head reassembly Figure 4 13 X ray head reassembly part two part three MD0361 4 16 4 4 EXCHANGING THE PRINTED CIRCUIT BOARDS Refer to fig
22. ase of transistor V19 is supplied with power supply synchronized positive half waves and a square wave collector output This output is differentiated by C8 and R30 The positive peak controls the transistor V20 diode V23 The inverted peaks are collected at base V21 when exposure button S27 is depressed V21 turns the timer on The voltage via dividers R31 R32 controls V20 and V21 as long as S27 is depressed 2 Since the capacitor C3 is not yet charged the transistor V12 is blocked V14 obtains base current through the resistor R12 R14 and is then switched through As a result the relays ER1 and ER2 energize 3 The emitter current of V14 flows through the potentiometer R13 and causes a voltage drop in it Itis thus possible to adjust the threshold voltage of the Schmitt trigger consisting of V12 V14 the transistor V12 can be controlled through only once its base voltage exceeds the value of 0 7v on 13 MD0361 3 9 1 57 TR 6 8 V6 12 15 17 19 20 8 158 45 8 10 27 23 x 3 3 x 222220 PDIP UDI e Measuring points tube current remove jumper QD X N Measuring point Figure 3 10 Schematic Heliodent 70 with dentotime MD0361 3 10 0 Switching Relay AR Refer to figure 3 10 1 As soon as the tube current allows
23. e device The protective device consists of a variety of slow and medium slow blow fuses Refer to figures 3 1 3 2 and 3 3 for the location of these devices 12 3 4in 325 128 PHYSICAL DESCRIPTION 9 3 8in 239 X ray control Weight 15 4 Lbs 7 kg Consists of eBase plate Line compensation transformer T3 with instrument circuit PCboardD5 Power supply PC board D3 and 22 digital instrument P 22 Object exposure time assembly with PC board D1 2 2 S BE K Figure 3 1 X ray control external view MD0361 3 2 Digital Voltmeter F1 P PC board D3 Circuit PC boards Protective device PC board D1 Fuse U1 0 16A 250 PC board D3 Fuse U2 10A 250 PC board D5 Fuse U3 10A 250 Fuse U4 1 5A 250 Fuse U5 10A 250 Fuse U6 10A 250 Fuse F1 0 063A 250 PC board D1 U1 U4 slow blow medium slow blow medium slow blow slow blow medium slow blow medium slow blow medium slow blow Figure 3 2 X ray control internal view Figure 3 3 Transformer outlet 115v MD0361 3 3 b X ray Head See figure 3 4 for the features of the X ray head 41 25 2 714 X ray head Weight 11 Lbs Consists of eHigh tension transformer H1 eHight voltage capacitor C1 e Voltage doubling circuit V10 eX ray tube filled aluminum housing for in sulation and cooling of the above c
24. e long arm number one and number two Refer to figure 4 7 and use the following steps No 04 13 94 91 MD0361 Mobile Spring Holder 99 Intermediate Piece 102 Bearings 104 Cylindrical Pins 112 Head Piece 113 Washers 116 Longeron Cover 119 Profile Tension Rear Hexagonal Head Screw Cover Head Piece Roller Hexagonal Head Screw Figure 4 7 Scissors cabling arm fitting part six a Place longeron cover 98 close enough to the arm that the mobile spring holder L lies on the head piece 94 b Pull cabling through the spring holder c Insert cabling flat in the longeron cover put on profile 99 and stick the two together with adhesive Make sure that the distances upwards and downwards are equal d Wait at least one hour for the adhesive to dry e Attach the tension rear 102 f Pull cabling through the intermediate piece g Check that the lead is in the correct position It must lie flat on the roller 116 in the intermediate piece h Place a washer between the head piece and the longeron cover on each side i Insert the hexagonal head screw 104 in such a way that it goes through the middle of the cabling Screw into the tension rear with about 10 rotations Fitthe other side of the scissors arm with the cover 112 profile 99 the hexagonal head screw 119 washers 97 and bearings 87 to the head piece 113 and the intermediate piece 86 in the same way Secu
25. e of the transformer voltage is added to the capacitor voltage so that twice the transformer peak voltage is required on the tube Refer to figure 3 9 Trans former 0 voltage Capacitor voltage Tube voltage diode voltage Figure 3 9 Transformer peak voltage doubling MD0361 3 8 c Line Input Fuses U2 and U3 protect the line input If the switch S1 is on the readiness indicating B1 lamp lights Refer to figure 3 10 d Control Transformer The control transformer ensures that the Heliodent 70 is always operated with a primary voltage of 125v in the line voltage range of 109v to 133v at 60 Hz 109v to 132v at 50 Hz The supply of the control transformer is changed to such an extent with the switch S6 as a function of the input voltage that a voltage of 125v is measured between the terminals T3 1 7 Refer to figure 3 10 e Start of Exposure Refer to figure 3 10 1 When you depress the exposure button S27 the relays ER1 and ER2 are controlled via V21 synchronized to the power supply The Schmitt trigger V12 V14 switches and the ER relay energizes 2 The relay contacts place the primary winding of the high voltage transformer H1 under voltage through the voltage divider R18 R20 At the same time the buzzer SU and the radiation indicator B2 are caused to operate They indicate the duration of the X ray radiation acoustically and optically f Exposure Current Path Refer to figure 3 10 1 The b
26. e the following procedures a Remove the cover and the aluminum disc b Connect the multimeter at leads 3 and 4 X ray head terminals are marked U and V c Select the range of 150vac d Make an exposure e Ifa voltage of 120v or less is present the X ray head is defective and you must exchange it Continue with Exercises MD0361 3 21 EXERCISES LESSON 3 INSTRUCTIONS Answer the following items by completing the statement or by writing the answer in the space provided at the end of the item After you have completed all of these items turn to Solutions to Exercises at the end of the lesson and check your answers with the solutions 1 The scissors arm spring supports the X ray head in a drift free condition When removing the X ray head which of the following cautions must you observe a b Remove the scissors arm before removing the X ray head Secure the scissors arm at a 45 angle before removing the X ray head Secure the scissors arm with a strap in a semi open position 6 inch separation Flatten the scissors arm to a 180 angle before removing the X ray head 2 Which of the following statements is true about the functioning of the Heliodent 70 a MD0361 The Heliodent 70 X ray tube is directly heated i e the heater and the high voltage are switched on simultaneously The Heliodent operates from the line with damping because the AR relay shorts the resistor R18 and separates the resist
27. e time improper timer function refer to Lesson 2 Verification Calibration of the Inter oral Dental X ray paragraph 2 5a through f 2 To determine if the malfunction is due to defective scissors arm wiring or a defective X ray head use the following procedures a Select the shortest exposure time 0 066 second b Make an exposure c Observe the red radiation emission light visual and the audible signal MD0361 3 16 d Determine if the red radiation emission light and the audible signal both come on simultaneously and go out simultaneously e If the indicators come on together but the exposure is noticeably longer 0 7 to 1 0 second expose a periapical film Develop the film 1 Determine that the X ray head needs replacement if the developed radiograph is blank transparent 2 Determine that the X ray head is OK but that the malfunction is in the scissors arm wiring if the developed radiograph is black 3 5 ISOLATE MECHANICAL MALFUNCTIONS a If the tube head does not rotate from stop to stop for 540 1 1 2 turns there is a malfunction in the rotational parts Refer to figure 3 14 540 Figure 3 14 Tube head rotational stop b If the X ray head does not return to 45 by itself when you release it the friction pad requires adjustment Refer to quarterly PMCS procedures in Lesson 1 paragraph 1 4b 3 a through e c If the tube head drifts the brake is malfunctioning Adjust the brake Refer
28. figure 3 10 j Forced Exposure Refer to figure 3 10 1 case of a defect where no tube current signal triggers the Dentotime there is a forced switching system The capacitor C7 is charged through the resistor R16 after switching on 2 If no tube current pulse triggers the Dentotime the transistor V6 is controlled through over R16 after approximately 0 7 to 1 sec and the timer circuit is actuated MD0361 3 11 Digital Voltmeter P Printed Circuit Board D3 Refer to figures 2 6 and 3 11 for printed circuit board D3 1 The digital voltmeter P receives a rectified filtered 12 5v measuring voltage proportional to a 125v line voltage input The power supply to the instrument consists of the transformer T1 D3 and a 5 volts direct current vdc circuit 2 The transformer T1 D5 supplies a line voltage proportional voltage This stabilized voltage is supplied to the Schmitt trigger The Schmitt trigger controls the respective leds red RT green GN and yellow GE via gates J3 and J4 If there is an over voltage condition the Schmitt trigger J5 output drives transistor V9 and relay AR 1 energizes interrupting the exposure circuit Digital voltmeter P 4 9 5 5 E 3 6 _ 98 75 802 03152 03 1 9 1 Resistor spindel Adj R7 2 2 Metal film resistor R8 3 3 Metal film resistor R6 10 4 MKT Capacitor C3 C4 C5 C6 4 5 Metal film resistor R2 R3 R4 R5 5 6 SI Diode EGB v3 4 7 SI Full wa
29. g to exactly the required length K 6 Replace old cabling with new cabling Refer to figure 4 6 and use the following steps a Push the new cabling 127 1 in the direction of the arrow 127 5 through the head piece 94 and pull it through the axle 21 Push back insulating hose 127 4 about 4 3 4 inches and push the cabling through the greenfield tubing 18 b Push the multi pin plug parts 19 and pouch 20 along as shown in figure 4 6 c Push the insulating hose 127 3 about 2 1 2 inches over cabling Push the shrink hose set of 5 127 2 about 1 2 inches over each single line d Check single lines from the other end of the cabling and connect corresponding multi pins numbers 3 4 5 6 e Leave ground lead on number one and number two free Shrink on the shrink hoses 127 2 with hot air Push forward the insulating hose 127 3 and assemble multi pin plug 19 f Fix the insulating hose 127 4 at the other end near the axle g Bolt the greenfield tubing onto axle Attach the strain relief F and pull the cabling back through head piece 94 h Fasten axle 21 with screws MD0361 4 9 Strain Relief 127 1 18 Greenfield Tubing 127 2 19 Multi pin Plug 127 3 20 Pouch 127 4 21 Axle 127 5 94 Head Piece 2 1 2in New Cabling Shrink Hose Set of 5 Insulating Hose Insulating Hose Arrow Figure 4 6 Scissors cabling arm fitting part five MD0361 4 10 7 Reassembl
30. he voltage values are not within one volt v the unit s must be calibrated before continuing See Lesson 2 Perform Verification Calibration of the Inter oral Dental X ray f Adjust the line compensation switch if necessary and verify the green led is on g Record the readings with no load h Setthe exposure time to 3 2 seconds and make an exposure i Record the readings of the unit s with a load Asillustrated in the example shown below determine the voltage drop under load by subtracting the voltage under load from the no load voltage NO LOAD VOLTAGE 125v minus VOLTAGE UNDER LOAD 120v VOLTAGE DROP 5v NOTE The maximum permissible voltage drop between the no load voltage and the voltage under load must not exceed 6 volts during the entire operation If the voltage drop exceeds 6 volts you must replace the power source 8 Verify the tube head current a Turn off the unit b Remove the 9 10 jumper circuit board D1 See figure 1 9 c Connect the multimeter to D1 9 10 See figure 1 9 MD0361 1 12 Figure 1 9 Tube head current verification MD0361 1 13 d Turn the unit on and allow 5 minute warm up period e Setthe multimeter to direct current milliampere dcma and range control to 10ma f Set the time selector to 2 0 seconds and make an exposure by holding the exposure button down g Ensure the buzzer sounds and the red radiation light comes on h Record the m
31. igits c Dc current 0 3 of reading plus 1 digit MD0361 1 4 2 Electromechanical pulse counter MODEL KESSLER ELLIS 203 1 pulse or equivalent 3 Regulating transformer stepless 90 150vac 50 volt amperes va 4 Medical equipment organizational maintenance tool kit 1 4 PERFORM PMCS ON A FIELD DENTAL X RAY UNIT There are four PMCS performed on the field dental X ray unit annual quarterly weekly and daily Different procedural steps apply to each one WARNINGS You must perform visual checks before connecting the unit to an adequate power supply During the exposure nobody should be inside the useful X ray beam The operator must be at least 6 feet away from the X ray head and not in the direction of the radiation Make full use of the length of the hand switch exposure cable a Annual PMCS Upon initial setup and annually thereafter you must service the X ray control to keep it in compliance with the DHHS Performance Standard 1 Check the exterior of the X ray using the following procedures a Verify that all labels are affixed and legible See figure 1 2 b Look for mechanical damage that may possibly affect radiation safety c Inspect the collimator for cracks d Test the tube head in all working positions for possible drift MD0361 1 5 This product complies with DHHS This product complics with DHHS regulations 21 CFR Subchapter J CONE TUBUS regulations
32. l pins and chains are not broken c The leveling devices are functional d The power supply is adequate MD0361 1 17 8 Based upon the illustration below what is the letter of the screw used to adjust the scissors arm if the angle is less than 45 degrees a A b B d D MD0361 1 18 9 Whatis the maximum permissible voltage drop between the no load voltage the voltage under load volts b 5 volts c 6 volts d 10 volts 10 Which of the following procedures must you do at least weekly a Wipe the equipment surfaces with a damp lint free cloth b Inspect the control and tube for burned light bulb c Verify the tube head current d Inspect the seat assembly 11 Before the machine is used which of these procedures must you perform as part of the daily PMCS a Wipe the equipment surfaces with a damp lint free cloth b Inspect components for rust cracks and wear c Adjust the scissors assembly spring to 45 degrees as necessary d Determine the voltage drop under load Check Your Answers on Next Page MD0361 1 19 SOLUTIONS EXERCISES LESSON 1 1 2 MD0361 a b figure 1 1 figure 1 1 figure 1 1 para 1 4a para 1 4a WARNING para 1 4 6 para 1 4b 1 e para 1 4b 3 d para 1 4b 7 j NOTE para 1 4c para 1 4d 3 End of Lesson 1 1 20 LESSON ASSIGNMENT LESSON 2 Perform Verification Calibration of the Inter o
33. l voltmeter Which of the following is the most probable malfunction a Pcb D1 b Pcb D3 c Pcb D5 d Pcb D7 7 When you troubleshoot the malfunction of no X rays emitting from the tube head after an exposure you use which of the following procedures a Connect crt screen b Turn up the lights to brighten surrounding area c Set exposure time to 3 0 sec d Make second test for electrical measurement Check Your Answers on Next Page MD0361 3 24 SOLUTIONS EXERCISES LESSON 3 1 2 MD0361 C para 3 2c CAUTION figure 3 6 para 3 3a 2 para 3 3g 1 para 3 4a para 3 5b para 3 6a para 3 7d 1 e End of Lesson 3 3 25 LESSON ASSIGNMENT LESSON 4 Remove and Replace Defective Modules in the Inter oral Dental X ray TEXT ASSIGNMENT Paragraphs 4 1 through 4 5 LESSON OBJECTIVES After completing this lesson you should be able to 4 1 Identify the steps required to remove and replace defective modules in the Inter oral Dental X ray 4 2 Identify the steps required to remove and replace defective printed circuit boards pcb s SUGGESTION After completing the assignment complete the exercises at the end of this lesson These exercises will help you to achieve the lesson objectives MD0361 4 1 LESSON 4 REMOVE AND REPLACE DEFECTIVE MODULES THE INTER ORAL DENTAL X RAY 4 1 GENERAL This lesson covers the general procedures for removing and replacing defecti
34. ling under Self Development School Code 555 A listing of correspondence courses and subcourses available through the Nonresident Instruction Section is found in Chapter 4 of DA Pamphlet 350 59 Army Correspondence Course Program Catalog The DA PAM is available at the following website http www usapa army mil pdffiles p350 59 pdf MD0361 ii LESSON ASSIGNMENT LESSON 1 Perform Preventive Maintenance Checks and Services on the Inter oral Dental X ray TEXT ASSIGNMENT Paragraphs 1 1 through 1 4 LESSON OBJECTIVES After completing this lesson you should be able to 1 1 Identify the components of the Inter oral Dental X ray 1 2 Identify the daily weekly monthly quarterly and annual Preventive Maintenance Checks and Services PMCS procedures for the Inter oral Dental X ray 1 3 Identify the equipment required to perform periodic PMCS on the Inter oral Dental X ray SUGGESTION After completing the assignment complete the exercises at the end of this lesson These exercises will help you to achieve the lesson objectives MD0361 1 1 LESSON 1 PERFORM PREVENTIVE MAINTENANCE CHECKS AND SERVICES ON THE INTER ORAL DENTAL X RAY 1 1 GENERAL To stay in compliance with the Department of Health and Human Services DHHS requirements you must maintain the Portaray Heliodent portable field dental X ray apparatus annually It is your responsibility to maintain the equipment with the manufacturer s recommended maintenance
35. ng Figure 4 3 Scissors cabling arm fitting part two MD0361 4 5 c Sever defective cabling 127 1 with wire cutters at the place indicated d Loosen the bolt connection B and pull the cabling out of the axle e Open the multi pin plug 19 f onto part C and unscrew the bolt connection D g Remove the greenfield tubing 18 completely h Unscrew the sleeve E backwards and remove the strain relief F i Screw out the locking screws push back part and unsolder the cabling 4 Prepare to remove cabling from scissors arm number two Refer to figure 4 4 for the following steps a Remove the two caps 85 and cover caps 84 on intermediate piece 86 as well as the cover caps 93 on the head pieces 94 and 113 b Relax the tension of the tension springs by means of the two hexagonal head screws 104 and 119 about 200 rotations required to relax tension springs WARNING It is imperative that you make sure that the tension of the springs is completely relaxed c Remove the safety strap 37 1 d Place the scissors arm on its base in such a way that both marking drill holes are shown upwards on the head pieces 94 and 113 e Adjust the head pieces by about 3 inches f Knock the cylindrical pins 91 which hold longeron cover 98 and cover 112 out downwards on both head pieces g On each of the two bearings 87 unscrew the cou
36. ng the pcbs a b C d You may exchange pcb D1 only with a soldering tool You may exchange pcb D3 only with a soldering tool You must use a soldering tool to exchange pcb D5 All pcb are factory calibrated and cannot be adjusted 9 Which of the following is a procedure you use to exchange the carrying case gasket a Remove the old gasket clean and reinstall b Clean the gasket retainer groove with a scraper C Use new adhesive to repair cuts in the gasket d Do not repair gaskets replace them MD0361 Check Your Answers on Next Page 4 21 SOLUTIONS EXERCISES LESSON 4 1 2 MD0361 a C para 4 2b 2 b para 4 20 3 9 para 4 2b 4 b para 4 20 5 0 para 4 2b 6 a para 4 2b 6 d para 4 3 1 2 para 4 4b para 4 5b End of Lesson 4 4 22
37. ntersunk screws and remove the bearings MD0361 4 6 113 93 94 98 84 Drill holes 93 Cover Cap 37 1 Safety Strap 94 Head Piece 84 Cover Cap 98 Longeron Cover 85 Cap 104 Hexagonal Head Screw 86 Intermediate Piece 112 Cover 87 Bearings 113 Head Piece 91 Cylindrical Pins 119 Hexagonal Head Screw Figure 4 4 Scissors cabling arm fitting part three MD0361 4 7 5 Remove the cabling from the scissors arms Refer to figure 4 5 for the following steps a Completely unscrew the two hexagonal head screws 104 and 119 b Turn away head piece 94 and remove longeron cover 98 86 94 98 99 102 104 112 113 119 New Cabling Intermediate Piece Head Piece Longeron Cover Profile Tension Rear Hexagonal Head Screw Cover Head Piece Hexagonal Head Screw Figure 4 5 Scissors cabling arm fitting part four MD0361 4 8 c Take out tension rear 102 d Pull defective cabling out of longeron 98 e Turn away head piece 113 on second arm f gt Remove cover 112 Pull defective cabling completely out of the scissors arm through intermediate piece 86 cover 112 and head piece 113 1 Remove the two profiles 99 and all remaining adhesive from longeron cover 98 and cover 112 Hold the severed cabling segments from the multi pin plug up against the defective cabling and shorten the new cablin
38. of the following responses correctly identifies an action you will take to install new cabling into the scissors arms a Push the insulating hose back 2 1 4 inches and push the cabling through the greenfield tubing b Push the insulating hose back 3 1 2 inches and push the cabling through the greenfield tubing c Push the insulating hose back 4 3 4 inches and push the cabling through the greenfield tubing d Push the insulating hose back 5 1 2 inches and push the cabling through the greenfield tubing MD0361 4 20 6 Which of the following responses correctly identifies an action you will take to install new cabling into the scissors arms a b C d Connect the cabling single lines to multi pin numbers 1 2 3 4 5 Connect the cabling single lines to multi pin numbers 2 3 4 5 Connect the cabling single lines to multi pin numbers 1 2 3 4 Connect the cabling single lines to multi pin numbers 3 4 5 6 7 inspect the rotational parts you remove the X ray head from the scissors arm Which of the following is a step you use a b Disconnect wires in the U channel but do not disconnect the ground wire Before you actually remove the X ray head check the rotational stop assembly When reassembling grease the bracket and secure the shaft with the bracket to the arm When reassembled verify you have rotation beyond 1 1 2 turns 8 Which of the following statements is true about exchangi
39. omponents e Lead shielded collimator Figure 3 4 X ray head MD0361 3 4 Scissors Arm Refer to figure 3 5 for the features and layout of the scissors arm The scissors arm is spring loaded to support the X ray head in a drift free condition over an operating range as shown A five conductor wiring harness connects the X ray head to the X ray control via the scissors arm ege aft n 1 743 wwe A iS r S ou MM ACA A ER M MAS Li EMT MEAS SIS TASH Figure 3 5 Scissors arm MD0361 3 5 CAUTION Removal of the X ray head requires securing the scissors arm in a semi opened position to prevent accidental opening spring loaded Refer to figure 3 6 CAUTION Figure 3 6 Scissors arm strap 3 3 HELIODENT 70 FUNCTIONING a Description of Function Refer to figure 3 7 the logic block diagram describing the functioning of the Heliodent 70 1 The Heliodent 70 X ray tube is indirectly heated i e the heater and the high voltage are switched on at the same time Thus tube current flows only once the emission temperature of the filament is reached after 150 to 250 msec millisecond As soon as the peak tube current exceeds a given value the Schmitt trigger V6 switches over the AR relay energizes and the timer circuit consisting of C3 R10 V12 V14 is triggered The AR relay shorts the resistor R18 and separates the resistor R20
40. or R20 from the power source The AR relay drops only as the trigger switch is released You measure the tube current between points X and Y since an alternating current flows there 3 22 tube current allows a voltage drop on resistor which is greater than U V4 2 4v U V5 0 7v U V6 0 7 which of the following occurs a Transistor V6 is controlled through R3 b Transistor V7 is controlled through R8 The V7 collector current stops the AR relay from drawing d The V6 collector current causes the AR relay to draw 4 You are troubleshooting an alert malfunction The radiation visible and audible indicators do not stop when you are testing the deadman feature Which of the following is the probable malfunction a The timer is functioning improperly or is maladjusted b The X ray head is defective and must be replaced scissors arm is defective and must be replaced d The pcb D1 is maladjusted or malfunctioning 5 You troubleshooting a mechanical malfunction You have released the scissors arm and the X ray head did not return to a 45 angle by itself Which of the following is the probable malfunction a The rotational parts are malfunctioning b The friction pad requires adjustment c The brake requires adjustment d The tube head needs replacement MD0361 3 23 6 You are troubleshooting circuit board malfunctions There is no display on the digita
41. quency compensated bleeder resistors and a spectrum analyzer b Tube current was measured by a dcma meter accuracy 1 5 percent accuracy at full scale The exposure time was measured with an oscilloscope and determined using the time of high voltage without the pre heat time d The cooling curve for the tube housing is steeper than is the curve for the anode because it is measured in 10 not 10 heat units HU Since the curve is steeper even though the anode cools in a shorter period of time the absolute rate of cooling for the tube housing is greater e When making x rays do not exceed the maximum cumulative HU For example if you make a series of exposures totaling 5000 HU and are required to repeat the series you must wait a minimum of 2 minutes before repeating the series In 2 minutes the unit will retain slightly less than 2000 HUs repeating a series generating 5000 HUs will raise the cumulative HUs to slightly less than 7000 2000 remaining HU from the original exposures 5000 new HUs from the repeat exposures MD0361 2 2 Rate maximum peak tube potential leakage technique factors 0 12ma is the equivalent maximum rated continuous tube current for 7ma with a duty cycle 1 60 70kv 70 0 12dcma Minimum filtration in useful beam 2 7mm Al at 70kv Cooling curve for the tube housing Figure 2 3 Anode cooling characteristic Figure 2 4 The tube is designed for self rectifying mode of opera
42. ral Dental X ray TEXT ASSIGNMENT Paragraphs 2 1 through 2 5 LESSON OBJECTIVES After completing this lesson you should be able to 2 1 Identify the procedures used to calibrate verify the Inter oral Dental X ray to include verifying the adequacy of the power supply calibrating the digital voltmeter and verifying calibrating the exposure time 2 2 Identify the calibration parameters for the Inter oral Dental X ray SUGGESTION After completing the assignment complete the exercises at the end of this lesson These exercises will help you to achieve the lesson objectives MD0361 2 1 LESSON 2 PERFORM VERIFICATION CALIBRATION OF THE INTER ORAL DENTAL X RAY 2 1 GENERAL To ensure that the Heliodent 70 portable dental x ray unit remains safe to operate and functions properly the x ray requires verification calibration You must perform this task at least annually Refer to paragraph 1 2 for a list of equipment you need to calibrate the x ray unit This lesson covers the following three verification calibration tasks verifying adequacy of the power supply calibrating the dvm and verifying calibrating exposure time 2 2 VERIFICATION CALIBRATION PARAMETERS When performing verification calibration refer to figures 2 1 2 2 2 3 2 4 and 2 5 for device acceptable performance parameters Measurement base of technique factors are as follows below a Kilovolt kv measurements were obtained using an oscilloscope with fre
43. re the scissors arm with the safety strap Attach the Heliodent generator m Add tension the tension springs n Counterbalance the weight as described in Lesson 1 Perform Preventive Maintenance Checks and Services on the Inter oral Dental X ray paragraph 1 4b 3 0 Replace all cover caps MD0361 4 12 4 3 REMOVING AND REPLACING ROTATIONAL PARTS When the tube head rotation is less than 540 and you have isolated the malfunction to the rotational parts you must inspect them You do this by removing the X ray head from the scissors arm as follows Refer to figures 4 8 through 4 13 a Secure the Safety Strap To facilitate the removal of the X ray head the scissors arm must be secured with the safety strap as shown in figure 4 8 Secure with tape Secure with tape Figure 4 8 X ray head removal part one MD0361 4 13 b Disassemble the Rotational Parts Refer to figure 4 9 Remove the cap and cover Disconnect wires in the U channel and ground wire A Refer to 4 9 Remove the cover 23 shown in figure 4 8 CAUTION The wires must be marked as follows below X ray tube assembly wires 3 4 5 6 Scissors arm wires 3 4 5 6 4 Remove the countersunk screw from the bracket 22 shown in figure 4 8 5 Hold X ray head at the yoke and remove the bracket 22 Remove the X ray head 6 Remove the clip ring 78 as shown in figure 4 10 7 Check the rotational stop assembly 3 p
44. tion with the Heliodent only Nominal tube current fixed 7dcma Nominal peak tube potential fixed 70kv Duty cycle 1 60 in seconds Figure 2 1 Calibration parameters 60 Hz 50 Hz Rated nominal line voltage 125 125y 230v 230v Permissible maximum line voltage regulation at terminal 6v 6v strip K3 Line voltage range 109 133v 108 132v 207 242v 207 240v Maximum line current at nominal values of 70kv and 125v 9 5 17 0a 7dcma 230v 5 0a 9 0a Generator duty cycle at the nominal values of 1 60 in sec 1 50 in sec 70kv 7dcma Maximum deviation from indicated valves a tube current nominal 7dcma 1 2dcma 1 b exposure time See Figure 2 5 20 2 54 Figure 2 2 Calibration voltage parameters MD0361 2 3 u xL 8 a TILIPELLITITTIL EE pet eae oll 25 eds ESSET 0 120 150 180 1 min Figure 2 3 Cooling curve for the tube housing HU x10 11111111 AN 2113 1 2 3 4 t min Figure 2 4 Anode cooling characteristic MD0361 2 4 NOMINAL Exposure time DENTOTIME MAXIMUM DEV
45. tional 6 Correct any minor deficiencies noted in PMCS 7 Record any deficiencies that are not corrected on a DA Form 2404 e Mechanical Damage Should mechanical damage affecting radiation be evident the apparatus may not be used until you correct the defect Continue with Exercises MD0361 1 15 EXERCISES LESSON 1 INSTRUCTIONS Answer the following items by completing the statement or by writing the answer in the space provided at the end of the item After you have completed all of these items turn to Solutions to Exercises at the end of the lesson and check your answers with the solutions SITUATION Use Exercise Figure 1 for items 1 3 Select from answers 1 8 Exercise Figure 1 1 Which number is the scissors arm 2 Which number is the X ray head 3 Which number is the transformer MD0361 1 16 4 Ataminimum how often must you service the X ray control to keep it in compliance with the DHHS Performance Standard a Annually b Quarterly c Weekly d Daily 5 Atleast how far away from the X ray head must you be when making an exposure a 3 feet b 5 feet c 6 feet d 10 feet 6 Onan annual basis you must change the desiccant bag Which of the following colors means not good a Red b Blue c Pink d White 7 During a quarterly PMCS you inspect the carrying case to ensure which of the following conditions a The adjustable brackets are operational b The dowe
46. to remove cover SIEMENS 109 133 Housing cover Figure 2 6 Digital voltage meter calibration MD0361 2 6 e Turn the unit and allow 5 minute warm up period f Compare the indicated value of the unit s dvm and the external multimeter 0 Adjust R7 on pcb D3 until the unit s dvm reading is the same as the multimeter connected across N and L See figures 2 5 and 2 6 1 To increase the voltage reading on the unit s turn R7 counterclockwise until it matches the reading with the multimeter connected across K3 N and L 2 To decrease the voltage reading on the unit s dvm turn R7 clockwise until it matches the reading with the multimeter connected across K3 N and L NOTE incoming line voltage must be between 109 and 133vac at 60 Hz or 109 and 132vac at 50 Hz for the unit to function properly 2 5 VERIFY CALIBRATE EXPOSURE TIME To perform the exposure time verification with a mechanical counter use the following procedures a Turn the unit off b Connect the counter to test points D1 4 and D1 21 on circuit board D1 See figures 2 7 and 2 8 MD0361 2 7 Digital voltmeter indus uo aq 530104 Bulinseay ONiNdVM 9 Indui surew 01 4099 0 1 9 4 534109 BA T 9 0 0 SMEE O 83 82 2 3 26
47. trol voltage increases further over voltage condition the output signal of J1 1 controlled via R10 switches from H to L 8 The output of J3 12 changes from L to H and 3 15 changes from H to L The light diode V7 green is de energized and light diode V5 red lights up 9 Ata control voltage corresponding to a line voltage of approximately 130 v the output signal of J5 1 controlled via R12 switches from H to L thus changing the output signal of J5 7 from L to H 10 Transistor V9 conducts AR 1 energizes thereby interrupts the exposure No exposure can be made MD0361 3 13 d 0 112 eet 83 18084117 gt 85014417 516 ZH 09 09 60 84 CU Figure 3 12 Pcb 05 schematic 3 14 MD0361 1 SI Z Diode EGB 2 Carbon resistor 3 Si npn transistor 4 Double OP Amplifier EGB Capacitor Metal film resistor SI Diode EGB 51 2 Diode Oo Ga As P Diode EGB 10 Carbon resistor 11 Ga P Diode EGB 12 Capacitor 13 Ga As P Diode EGB 14 Metal film resistor MD0361 v8 R6 R7 R13 v9 11 15 C3 R5 R14 R15 R18 R19 v2 V3 V4 V5 R8 7 c2 V6 R1 R2 R3 Figure 3 13 Pcb D5 3 15 15 16 17 18 19 20 21 22 23 24 25 26 27 Voltage regulator EGB Resistor spindel Adj Metal film resistor Capacitor Power inverter EGB Capacitor 51 Rectifier set EGB Flat transformer AND Gate 4x2 EGB Relay Ceramic Capacitor Metal film resistor
48. ure 4 14 Figure 4 14 Printed circuit board replacement a You may exchange pcbs D1 and D3 with the aid of a screwdriver b You must use a soldering tool to exchange pcb D5 C All pcbs are factory calibrated To adjust pcb D1 refer to Lesson 3 Perform Verification Calibration of the Inter oral Dental X ray 4 5 EXCHANGING THE CARRYING CASE GASKET If when you inspect the carrying case you find a mechanical defect to the gasket cuts frayed and so forth is visible you must exchange it Refer to figure 4 15 a Remove the old gasket b Clean the gasket retainer groove with a scraper to remove old adhesive Apply new adhesive per manufacturer s instruction 2 Install a new gasket MD0361 4 17 Figure 4 15 Carrying case gasket Continue with Exercises 4 18 MD0361 EXERCISES LESSON 4 INSTRUCTIONS Answer the following items by completing the statement or by writing the answer in the space provided at the end of the item After you have completed all of these items turn to Solutions to Exercises at the end of the lesson and check your answers with the solutions 1 Which of the following responses concerning removal of the generator to install new cabling is correct a You should secure the safety strap to the scissors arms with adhesive tape b You should completely remove the safety strap from the scissors arms C You should loosen the safety strap until the scissors arm is open abo
49. ut 10 inches d You should tighten the safety strap until the scissors arm is completely closed 2 Which of the following responses correctly identifies an action you take in preparing to remove cabling from scissors arm number one a Leave the greenfield tubing in place b Remove only that portion of the greenfield tubing required to pull the cabling out of the axle c Remove the greenfield tubing completely d After removing the greenfield tubing sever the cabling MD0361 4 19 3 Which of the following responses correctly identifies an action you take preparing to remove cabling from scissors arm number two a Do not relax the tension of the tension springs b Relax the tension springs by means of the two hexagonal head screws about 200 rotations are required c Relax the tension springs by means of the two hexagonal head screws about 50 rotations are required d Only relax the tension springs if there is too much tension to easily remove the cylinder pins by hand 4 Which of the following responses correctly identifies an action you take to remove cabling from scissors arm number two a Leave the two profiles attached to the longeron cover and longeron b Partially unscrew the two hexagonal head screws c Pullthe cabling out of the scissors arm through the intermediate piece cover and head piece d Do not take out the tension rear unless you cannot otherwise remove the headpiece 5 Which
50. ve modules in the Heliodent 70 Portable X ray Unit The modules selected represent a portion of the total number of modules in this piece of equipment The skills required to remove and replace these modules are transferable to removing and replacing all modules The modules covered are scissors arm cabling rotational parts pcb and the carrying case gasket 4 2 EXCHANGING SCISSORS ARM CABLING If the cabling in the scissors arm of the dental X ray unit is damaged you should return the defective scissors arm to SIEMENS MEDICAL SYSTEMS INC Dental X Ray Division If you cannot return the defective scissors arm you will need to remove and replace it To remove and replace the cabling you will use the materials in paragraph a and the procedures in paragraph b below a Materials For the fitting of a new cabling you need the following articles cabling 2 profiles a set of 5 shrink length 1 2 inch insulating tubing lengths of 2 1 2 inches and 4 3 4 inches and adhesive b Procedures Refer to figure 4 1 1 Prepare the scissors arm a Unplug the unit from the power source b Put the safety strap 9 in place c Disengage the scissors arm assembly 10 from the coupling as shown in figure 4 1 d Disconnect multi pin plug 11 by unscrewing the lock ring in the direction of the arrow e Place the protective sleeve over the multi pin connector 11 f Route the greenfield tubing and tighten the strap securing the arms
51. ve rectifier EGB 2 5 11 8 f F1 4 12 9 Ceramic Capacitor C2 7 10 Volt Regulator EGB 11 11 Elko 1 8 13 12 Metal film resistor R1 13 SI Full wave rectifier EGB V1 14 Transformer Figure 3 11 Pcb D3 MD0361 3 12 l Line Voltage Indication and Over Voltage Exposure Interruption Printed Circuit Board D5 Refer to figures 3 12 and 3 13 1 The 15v stabilizer receives its input voltage from the power supply of the timing switch board D1 The transformer T1 D5 supplies via rectifier V1 the voltage for the Schmitt triggers J1 and J5 2 zener diodes V3 and V4 increase the value of the R C circuit R8 C3 and R5 C4 smoothes the signal input to the Schmitt trigger J1 2 J1 6 J5 2 3 Atalower control voltage the Schmitt trigger 41 1 and J1 7 signals are at H via the inverter J3 and the AND gate J4 inverter J3 10 signals L the light diode V6 yellow lights up 4 Asthe control voltage increases the output signal of Schmitt trigger J1 7 changes to L controlled by R11 The output signal of the inverter J3 10 signals L the light diode V6 yellow lights up 5 Asthe control voltage increases the output signal of Schmitt trigger 41 7 changes to L controlled by R11 The output signal of the inverter J3 10 changes from L to H 6 The light diode V6 is de energized J3 12 in turn switches to output from H to L and the light diode V7 green lights up nominal unit operating condition 7 Asthe con
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