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HP 10811A, Operating & Service Manual

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HP 10811A Operating & Service Manual Download Page 47

Model 10811A/B 

 

39

SECTION VIII  

SERVICE 

8-1.   INTRODUCTION 

8-2.  

This section contains theory of operation, a detailed troubleshooting procedure, and a schematic 
diagram. 

8-3.  SCHEMATIC DIAGRAM SYMBOLS AND REFERENCE 
DESIGNATORS 

8-4.  

Figure 8-1

 shows the symbols used in the schematic diagram. At the bottom of 

Figure 8-1

, the 

system for reference designators, assemblies, and subassemblies is shown. 

8-5.   REFERENCE DESIGNATORS 

8-6.   Theory of Operation 

8-7.  

The overall theory of operation for the 10811A/B starts with 

paragraph 8-9

. The detailed theory of 

operation starts with 

paragraph 8-13

. 

8-8.   OVERALL BLOCK DIAGRAM THEORY 

8-9.  

The 10811A/B Quartz Crystal Oscillator is an extremely stable, compact, low-power source of 10 
MHz. The crystal, along with the oscillator, circuit buffer amplifier, and oven control circuits are all 
mounted inside a thermally insulated housing. 

8-10.   A detailed block diagram of the 10811A/B oscillator is shown in 

Figure 8-2.

 

8-11.   The 10811A/B oscillator is divided into three sections with each section connected by a .010-inch 

thick flexible circuit. Three small circuit boards are bonded to the flexible circuit to provide support 
in the areas where components are located. The arrangement allows the unit to be easily 
disassembled and operated in the disassembled state on the service bench. 

8-12.   The three sections can be divided into the following subsections (

Figure 8-2

): 

1. Main 

Oscillator 

2.  Automatic Gain Control 

Voltage Reference (+5.7V and +6.4V)  
Output Impedance Matching Buffer 

3.  Output Buffer Amplifier 

Oven Controller 

Summary of Contents for 10811A

Page 1: ...xist and as such the user of this document should take care and use common sense when referencing this documentation Copyright Notice This documentation is Copyright 1980 Hewlett Packard and Copyright 2006 Jack Hudler hpdocs hudler org Permission to use and redistribute this documentation for non commercial and internal corporate purposes is hereby granted free of charge Any redistribution of this...

Page 2: ...Model 10811A B Page Intentionally Left Blank ...

Page 3: ...Model 10811A B ...

Page 4: ...umber 2028 Also covers oscillators with HP Part Numbers 10811 60101 and 10811 60105 OTHER SERIAL PREFIXES For serial prefixes above 2028 a Manual Change sheet is included with this manual First Edition August 1980 Copyright 1980 by HEWLETT PACKARD COMPANY 5301 Stevens Creek Blvd Santa Clara CA 95050 All Rights Reserved MANUAL PART NUMBER 10811 90002 Microfiche Part Number 10811 90003 ...

Page 5: ...TIONS HP INSTRUMENT 10 2 28 OPERATING ENVIRONMENT 10 2 34 STORAGE AND SHIPMENT 11 2 35 Environment 11 2 37 PACKAGING 11 2 38 Original Packaging 11 2 40 Other Packaging 11 III OPERATION 12 3 1 INTRODUCTION 12 3 3 BASIC POWER UP DESCRIPTION 12 3 7 FREQUENCY ADJUSTMENT 12 3 9 FREQUENCY ADJUSTMENT PROCEDURE 12 3 10 ACCURACY VS ADJUSTMENT INTERVAL 13 IV OPERATIONAL VERIFICATION 16 4 1 INTRODUCTION 16 4...

Page 6: ...T IMPEDANCE MATCHING AND OUTPUT BUFFER 45 8 25 VOLT AGE REFERENCES 5 7V AND 6 4V 45 8 27 OVEN HEATER AND CONTROLLER THEORY 46 8 35 PRECISION VOLTAGE REFERENCE 47 8 37 OVEN CONTROLLER TURN ON CURRENT LIMITING 47 8 39 HEATER TRANSISTOR BALANCE 48 8 41 REPAIR AND TROUBLESHOOTING 49 8 42 Inspection 49 8 44 REPAIR 49 8 45 Printed Circuit Component Replacement 49 8 47 Replacing Integrated Circuits 49 8 ...

Page 7: ...ly and Output Connections 8 Figure 2 4 10811B Supply and Output Connections 9 Figure 2 5 Mechanical Mounting Dimensions 10 Figure 3 1 Oscillator Adjustment Set Up 13 Figure 4 1 BASIC Program 21 Figure 4 2 HPL Program 21 Figure 5 1 Oscillator Adjustment Setup 26 Figure 5 2 10811A Amplitude Adjustment Set up 27 Figure 5 3 108118 Amplitude Adj Set up 28 Figure 8 1 Schematic Diagram Notes 40 Figure 8 ...

Page 8: ...ett Packard Fundamentals of Quartz Oscillators 4 U S National Bureau of Standards Monograph 140 Time and Frequency Theory and Fundamentals available from Superintendent of Documents U S Government Printing Office Washington D C 20402 5 In 1990 the NIST replaced the Monograph 140 document with this interim collection of documents NIST TN1 339 or visit time NIST Time and Frequency Publication Databa...

Page 9: ...Model 10811A B 1 Figure 1 1 10811A and 108118 Oscillators ...

Page 10: ...o the instrument is a serial number plate The serial number is in the form 0000A00000 It is in two parts the first four digits and the letter are the serial prefix and the last five are the suffix The prefix is the same for all identical instruments it changes only when a change is made to the instrument The suffix however is assigned sequentially and is different for each instrument The contents ...

Page 11: ...Steady state power drops to a typical value of 2 0W at 25 C in still air with 20 Vdc applied Connectors 10811A Mates with CINCH 250 15 30 210 HP 1251 0160 or equivalent not supplied 10811B Solder terminals and 5MB Snap on connectors Mates with Cablewave Systems Inc 700156 or equivalent not supplied Accessories Available Service Manual HP 10811 90002 not supplied This Manual Size 72 mm X 52 mm X 62...

Page 12: ...nto service 1 17 The 10811A B requires two external power supplies The power supply requirements are listed in Section II 1 18 The 10811A and 10811B are identical except for the connections The 10811A uses a standard 15 pin printed circuit connector The 10811B uses filtered feedthrough terminals for power and oven monitor and 5MB subminiature rf snap on connections for the 10 MHz output and EFC 1 ...

Page 13: ...t 10 MHz 3406A 6 General Purpose Bandwidth 10 MHz 1740A Oscilloscope 7 Frequency Doubler Operates at 10 MHz 10515A 8 Mixer Amplifier 10 MHz Mixer 50 dB gain K79 59992A 9 Spectrum Analyzer 10 MHz 70 dB range 8552B 8553B 10 Power Supply 480 mA 20V 2 required 6215A 11 DC Voltmeter Any HP type digital or analog 12 Torque Screwdriver 2 30 inch lb 0 2 to 3 4 newton meters 8730 0012 13 Feedthru Terminati...

Page 14: ...llator circuitry and the other supplies power to the oven heaters Table 2 1 lists the required supply voltages and the effect of a change in these voltages on the output frequency Table 2 1 Input Voltages Voltage Coefficients Voltage Coefficients Input Circuit Required Voltage Required Current Power Voltage Change Frequency Change 1 2 X 10 10 Oscillator Amplifier 11 0 13 5V dc Noise 100 µV 30 mA t...

Page 15: ...quency will go lower Conversely as the EFC voltage goes negative the output frequency will go higher 2 14 Since noise on the EFC line affects the oscillator s stability noise appears as FM on the output care must be taken to ensure that a relatively noise free EFC voltage source is used The noise level must be kept below 100 µV to maintain good stability performance 2 15 The EFC input should be co...

Page 16: ...rcuit is 10 000 ohms Figure 2 2 shows an oven monitor LED indicator circuit Figure 2 2 Oven Monitor LED Circuit 2 20 MATING CONNECTORS AND MOUNTING 2 21 The 10811A Oscillator requires a 15 pin printed circuit connector The recommended connector is the CINCH 250 15 30 210 HP 1251 0160 The 10811A can be secured with two 6 32 screws 1 4 inch long Figure 2 3 shows the power supply connection for the 1...

Page 17: ... mate to Cablewave Systems Inc 700156 or equivalent HP Part No 1250 0885 not supplied Figure 2 4 shows the connections for the 10811 B Oscillator Figure 2 4 10811B Supply and Output Connections 2 23 INSTALLATION INSTRUCTIONS 2 24 Figure 2 5 shows the mechanical mounting dimensions of the 10811A B Oscillators for use in custom installation Since all quartz oscillators are sensitive to shock vibrati...

Page 18: ...hat instrument should be consulted to see if an oscillator support board power supplies is required Once the support board is installed the 10811A can be installed in place of the 10544A Consult your nearest sales and service office for more details 2 28 OPERATING ENVIRONMENT 2 29 TEMPERATURE The 10811A B may be operated in temperatures from 55 C to 71 C 2 30 MAGNETIC FIELDS Sidebands due to 0 1 m...

Page 19: ...del number and full serial number 2 40 Other Packaging 2 41 The following general instructions should be used for repacking with commercially available materials 1 Wrap instrument in heavy paper or plastic If shipping to Hewlett Packard office or service center attach tag indicating type of service required return address model number and full serial number 2 Use strong shipping container A double...

Page 20: ...ximum This lasts less than second and is a typical circuit action 3 6 After the first 10 minutes have passed the oscillator may be initially adjusted using the following procedure The oscillator should be readjusted after 24 hours for maximum accuracy Periodic adjustment schedule can be determined by the procedure described in paragraph 3 10 3 7 FREQUENCY ADJUSTMENT 3 8 The frequency adjustment is...

Page 21: ...cilloscope pattern 1 div X 01 μs div 01 μs t time required for Δt to occur Figure 3 1 Oscillator Adjustment Set Up 3 10 ACCURACY VS ADJUSTMENT INTERVAL 3 11 Table 3 1 shows the required adjustment interval to maintain a required accuracy If the aging rate is known to be 3 x 10 10 day then a more precise adjustment interval can be determined The specification for aging is 5 X10 10 day but aging is ...

Page 22: ...zontally to the left and read the minimum calibration interval in days maximum allowable error known aging rate per day calibration interval in days Example 5 x 10 9 maximum allowable error 3 x 10 10 day known aging rate 16 67 days 17 days 3 X 10 10 day known aging rate 3 13 From Table 3 1 the oscillator should be adjusted approximately every 17 days 3 14 The minimum calibration interval may also ...

Page 23: ...Model 10811A B 15 Page Intentionally Left Blank ...

Page 24: ... given in the table may be substituted for the recommended model s 4 7 TEST RECORD 4 8 Results of the Operational Verification Table 4 2 may be tabulated on the Operational Verification Record Table 4 4 4 9 If the 10811A B Oscillator is to be tested outside its normal installation a special test connector may be used for applying power to the oscillator The connector also has a BNC connector for t...

Page 25: ...10 12 for 1 second averaging 1 X 10 11 for 10811 60105 a Equipment required 5065A Rubidium Vapor Frequency Standard 5061A Option 004 or 105A B See Table 1 2 HP Model 5390A may be used in place of the following 10830A Mixer 5345A Electronic Frequency Counter with Option 011 9825A Calculator with 98210A and 98213A or 98214A or 98216A 98034A HP IB Interface 10515A Doubler 6 Plug AC Power Strip 3 BNC ...

Page 26: ...EL 10 LOG LINEAR Switch 10 dB LOG b Connect the output of the 10811A B to the spectrum analyzer input c Apply power to the oscillator and spectrum analyzer Allow 10 minutes for oscillator to stabilize d Adjust Spectrum Analyzer FREQUENCY control so that 10 MHz signal is at left edge of display center frequency approximately 35 MHz e Adjust LOG REF LEVEL vernier control right hand knob so that 10 M...

Page 27: ...e model 5390A frequency stability analyzer is available it should be used in place of the text described below Follow instructions in the 5390A operating manual to make measurement a Connect the equipment as follows NOTE Arrange the instruments as shown Keep all signal leads away from power cords and HP IB cable DO NOT FORGET THE 10515A DOUBLER ON THE 5065A OUTPUT Connect all ac power to the same ...

Page 28: ...oscillator are the oven and oscillator power supplies These must be stable in order for the circuits to function properly See Table 1 1 Specifications and paragraph 2 6 for power supply noise requirements 5 Long Term Stability NOTE The 10811A B will typically take 24 to 48 hours to reach its specified aging rate after storage or shipment In some cases if extreme environmental conditions were encou...

Page 29: ...Model 10811A B 21 Figure 4 1 BASIC Program 4 13 OPTIONAL CONTROLLERS AND COUNTERS 4 14 Optional Controllers 4 15 Figure 4 2 lists the program for the 9825A Calculator Figure 4 2 HPL Program ...

Page 30: ...he program codes set required when using the 5316A counter Replace line 4 HPL or line 40 BASIC with the appropriate codes Be sure the optional counter address is set to 18 5316A gate time must be set manually to 1 s on the front panel Table 4 3 5316A Program Codes ...

Page 31: ...Model 10811A B 23 Page Intentionally Left Blank ...

Page 32: ...Model 10811A B 24 Table 4 4 Operational Verification Record ...

Page 33: ...Schematic Diagrams 5 9 SAFETY CONSIDERATIONS 5 10 This section contains warnings and cautions that must be followed for your protection and to avoid damage to the equipment WARNING MAINTENANCE DESCRIBED HEREIN IS PERFORMED WITH POWER SUPPLIED TO THE INSTRUMENT AND PROTECTIVE COVERS REMOVED SUCH MAINTENANCE SHOULD BE PERFORMED ONLY BY SERVICE TRAINED PERSONNEL WHO ARE AWARE OF THE HAZARDS INVOLVED ...

Page 34: ...3 Offset Calculation a By timing the sideways movement divisions per second on the oscilloscope the approximate offset can be determined based on the oscilloscope sweep speed as shown below b For example if the trace moves 5 divisions in 10 seconds and the sweep speed is 0 01 μs div the oscillators signal is within 5 X 10 9 of the reference frequency The calculation can also be made as follows Whe...

Page 35: ... allow oscillator to cool if previously operated To remove cover a For the 10811A remove the three screws securing the bottom cover Remove the two screws securing the P c edge connector to the outer can Remove the top foam insulator to expose the oscillator circuits CAUTION DO NOT pull the oscillator out of the outer housing by pulling on the P C edge connector or flex circuit b For the 10811B rem...

Page 36: ... apply power to the oven circuits c For the 10811B reconnect the flex circuit attached to the bottom cover and connect the 6215A as shown in Figure 5 3 DO NOT APPLY POWER TO THE OVEN CIRCUITS A Micon to BNC adaptor is available for the 10 MHz output HP Part Number 05060 6116 d For both 10811A and B turn on the 6215A power supply and adjust R6 AGC control for 55V rms 50 mV as read on the 3406A Samp...

Page 37: ...rt in a five digit code see list of manufacturers in Table 6 2 c Manufacturer s part number d Total quantity used in the instrument Qty column 6 3 ORDERING INFORMATION 6 4 To obtain replacement parts address order of inquiry to your local Hewlett Packard Sales and Service Office see lists at rear of this manual for addresses Identify parts by their Hewlett Packard part numbers a Instrument model n...

Page 38: ...d 0370 Knobs Control 0380 Crystals 0470 Adhesives 0490 Relays 0510 Fasteners 0674 through 0778 Resistors Fixed non wire wound 0811 through 0831 Resistors wire wound 1200 Sockets for components 1205 Heat Sinks 1250 Connectors RF and related parts 1251 Connectors non RF and related parts 1410 Bearings and Bushings 1420 Batteries 1820 Monolithic Digital Integrated Circuits 1826 Monolithic Linear Inte...

Page 39: ...d Parts 6 15 Some of the values in the parts list are selected during manufacture to meet circuit requirements These parts are marked with an asterisk in the parts list and schematic diagrams with average values shown 6 16 The 10811A B Oscillator contains only one factory selected part which is R20 OVEN TEMPERATURE SET resistor This resistor is supplied with the crystal should the crystal require ...

Page 40: ...0 0353 3 1 INDUCTORRF CH MLD 430hN 1 10SDX 26LG 28480 9140 0353 L4 9100 2276 9 1 INDUCTORRF CH MLD 100uH 10 10SDX 26LG 28480 910002276 LS 9100 2280 5 INDUCTORRF CH MLD 220uH 10 10SDX 26LG 28460 9100 2250 L6 9100 2280 5 INDUCTORRF CH MLD 220uH 10 10SDX 26LG 28480 910002280 L7 9100 2280 5 INDUCTORRF CH MLD 220uH 10 10SDX 26LG 28480 9100 2280 L8 9100 2280 5 INDUCTORRF CH MLD 220uH 10 10SDX 26LG 28480...

Page 41: ... 825 1 05W F TC 0 100 24546 C3 1 8 T0 825R G R20 0698 7235 6 2 RESISTOR 909 1 05W F TC 0 100 24546 C3 1 8 T0 909R G R20 0698 7236 7 1 RESISTOR 1K 1 05W F TC 0 100 24546 C3 1 8 T0 1001 G R20 0698 7237 8 1 RESISTOR 1 1k 1 05W F TC 0 100 24546 C3 1 8 T0 1101 G R20 0696 7238 9 1 RESISTOR 1 21K 1 05W F TC 0 100 24546 C3 1 8 T0 1211 G R20 0698 7239 0 1 RESISTOR 1 33K 1 05W F TC 0 100 24546 C3 1 8 T0 133...

Page 42: ...R W XISTOR CUT OUTS 28480 10811 20202 MP3 10811 20203 1 MASS COVER W TUNING CAP HOLE 28480 10811 20203 0520 0166 8 SCREW 28480 0520 0166 10811A MECHANICAL PARTS MP4 10811 20206 1 OUTER HOUSING FOAMED 28480 10811 20212 MP5 10811 20211 1 BOTTOM COVER 28480 10811 20211 MP6 10811 40001 1 FOAM COOKIE UNDER BOT COV 28480 10811 40001 10811A MISCELLANEOUS PARTS 3030 0827 2 SCREWS FOR P C CONNECTOR 28480 3...

Page 43: ... AZ 85062 07263 FAIRCHILD SEMICONDUCTOR DIV MOUNTAIN VIEW CA 94042 24546 CORNING GLASS WORKS BRADFORD BRADFORD PA 16701 25088 SIEMENS CORP ISELIN NJ 08830 27014 NATIONAL SEMICONDUCTOR CORP SANTA CLARA CA 95051 28480 HEWLETT PACKARD CO CORPORATE HQ PALO ALTO CA 94304 30983 MEPCO ELECTRA CORP SAN DIEGO CA 92121 51642 CENTRE ENGINEERING INC STATE COLLEGE PA 16801 72982 ERIE TECHNOLOGICAL PRODUCTS INC...

Page 44: ...Model 10811A B 36 Page Intentionally Left Blank ...

Page 45: ...manuals for these instruments will be supplied with Manual Changes pages containing the required information to update the manual Replace affected pages or modify existing manual information as described in the Manual Changes pages See Section VI of this manual for a description of board identification If the series number etched or stamped on any circuit board or circuit board assembly is higher ...

Page 46: ...Model 10811A B 38 Page Intentionally Left Blank ...

Page 47: ...ely stable compact low power source of 10 MHz The crystal along with the oscillator circuit buffer amplifier and oven control circuits are all mounted inside a thermally insulated housing 8 10 A detailed block diagram of the 10811A B oscillator is shown in Figure 8 2 8 11 The 10811A B oscillator is divided into three sections with each section connected by a 010 inch thick flexible circuit Three s...

Page 48: ...Model 10811A B 40 Figure 8 1 Schematic Diagram Notes ...

Page 49: ...TPUT AMPLIFIER AND VOLTAGE REFERENCE B GROUND POINT FOR TESTING OVEN CONTROLLER B GROUND POINT FOR TESTING OVEN CONTROLLER A AND B GROUNDS MAY BE TIED TOGETHER OR FLOATED AT DIFFERENT POTENTIALS EXTERNAL TO THE OSCILLATOR Figure 8 2 10811A B Overall Block Diagram ...

Page 50: ...of C5 L2 C6 and L3 C5 is a dc blocking capacitor Its reactance is very low so the combination of these components can be redrawn as in Figure 8 4 The crystal Y1 is a third overtone crystal and is operated at 10 MHz To keep the circuit from oscillating at the crystal s fundamental or at a different overtone the mode suppression network of C5 L2 C6 L3 appears capacitive only at frequencies between 9...

Page 51: ...or a fine tuning control a varactor CR1 is added in parallel with C1 tuning capacitor See Figure 8 6 The varactor s capacitance depends on the dc voltage applied to it reverse bias The HC voltage range is 5 volts to 5 volts giving a fine tuning range of 1 Hz 1 X10 7 Since one side of the varactor is tied to a reference 6 4V a full 5 volts applied to the HC input will still keep CR1 reverse biased ...

Page 52: ...uit changes This change in the AGC voltage changes the voltage applied to the base of Q1 and stops the impending output voltage change A peak detector circuit formed by C12 CU CR4 and CR5 is used to develop a dc voltage to control the crystal current This negative control voltage forms the lower half of a voltage divider for the base of Q1 R6 and R7 Controlling the bias current and the gain of Q1 ...

Page 53: ...gnal is then applied to the output buffer stage of Q9 Resistor R40 provides the 50Ω source impedance when transformed by T1 Typical gain from Q9 base to collector is approximately 2 See Figure 8 8 Figure 8 8 Output Amplifiers 8 25 VOLTAGE REFERENCES 5 7V AND 6 4V 8 26 Constant current diode CR2 feeds 1 mA to zener diode CR3 providing 6AV dc for the EFC varactor reference R12 and C15 form a filter ...

Page 54: ...his voltage change and then uses it to control the current through Q7 and Q8 The current flowing through transistors Q7 and Q8 causes power dissipation in the form of heat and it is this heat that warms the oven mass Therefore when the mass temperature starts to change the heaters are told to adjust their power to cancel the impending temperature change 8 31 WARM UP GENERAL OPERATION If the oscill...

Page 55: ...ference It provides a stable voltage source for the bridge and U1 A change in the bridge reference voltage changes the voltage across the thermistor and hence the power it dissipates See Figure 8 10 8 37 OVEN CONTROLLER TURN ON CURRENT LIMITING 8 38 Figure 8 11 shows the turn on current limiting circuit From an initial turn on condition the thermistor senses the oven temperature to be low To corre...

Page 56: ...tween the two transistors Figure 8 12 shows a simplified schematic of this circuit Amplifier U1A references a voltage divider across Vcc R25 R26 and a divider referenced to the mid point between the heater transistors From this U1A controls the base current of Q7 to insure the Voltage at the mid point between the heater transistors is a constant percentage of Vcc V4 0 57 Vcc 2 Figure 8 12 Heater T...

Page 57: ...8 47 Replacing Integrated Circuits 8 48 Following are two recommended methods of replacing integrated circuits a SOLDER GOBBLER This is the best method Solder is removed from board by a soldering iron with a hollow tip connected to a vacuum source b CLIP OUT Clip the leads as close to the component as possible With a soldering iron and long nose pliers carefully remove the leads from each hole The...

Page 58: ...Output is off frequency high or low 5 Output has excessive noise or frequency stability does not meet specifications 8 53 Poor frequency stability can be difficult to troubleshoot and many times the oscillator is not at fault Environmental conditions can affect stability and should be ruled out first 8 54 Failures in the oven circuitry can be divided into the following problems 1 No oven current h...

Page 59: ...g the oven controller stop here and go to paragraph 8 69 Continue only if the trouble is in the oscillator circuit The following steps will be performed for both oscillators Step 6 Using a long small diameter tool remove the complete oscillator assembly by inserting the tool into the tuning capacitor access hole labeled FREQ ADJUST and pushing on the capacitor until the circuit can be grasped and ...

Page 60: ...e input leads for the oscillator circuits power and the oven heaters and controller circuits b 10 MHz output through a female BNC c Oven monitor output for connection to a voltmeter d HC input connection to ground Figure 8 13 10811A B Special Test Connector 8 63 The following parts are required to construct the special test connector a 15 pin pc board connector HP part number 1251 0494 b 6 banana ...

Page 61: ... are the oven controller power supply inputs j Twist together the remaining wire connected to 15 S and the wire connected to pin 11 M This is the oven monitor output k Twist together the two wires connected to pins 2 B and 3 C These are the oscillator supply input l Connect one banana plug to the free end of each wire m Label each banana plug as follows Wire connected to Label as pin 2 B oscillato...

Page 62: ...replaced HP Part Number 10811 60107 Once the insulating foam is attached to the bottom cover feedthroughs and terminals cannot be replaced without impairing the heat insulating abilities of the bottom cover Do not attempt to repair the cover or replace the flex circuit Table 8 1 Temperature Set Resistor List OVEN TEMP C RESISTOR VALUE PART NUMBER 80 0 1 33K 0698 7239 80 1 1 29K 0698 6981 80 2 1 25...

Page 63: ...sistors when the oven mass has reached operating temperature After power cut back this circuit monitors the oven mass temperature and controls the power in the heaters to maintain the constant temperature The thermistor RT1 has a negative temperature coefficient At room temperature the thermistor resistance is approximately 100K ohms while at operating temperature 82 C the resistance is approximat...

Page 64: ...e this indicates a trouble in the warm up current limit circuit or the current control and heater circuit If shorting the thermistor reduces the current being drawn from the power supply this indicates the current control circuit is operating and the problem is most likely in the warm up current limit circuit 8 78 As with most troubleshooting trees this is intended to be a guide to the trouble are...

Page 65: ...Model 10811A B 57 Table 8 2 Oven Controller Troubleshooting Tree ...

Page 66: ...matic diagram 8 88 OSCILLATOR TROUBLESHOOTING TECHNIQUES 8 89 When troubleshooting the oscillator section remove the oven mass from the housing and the covers from the oven mass as described in paragraph 8 59 Connect 12V to the oscillator section use special connector described in paragraph 8 61 for 10811A connect power to T1 1 and oscillator circuit common in 10811B Set the power supply current l...

Page 67: ...aragraph 8 68 b Special Parts Consider ations If the circuit will still not oscillate the problem is most likely one of the oscillator circuit elements 8 96 OUTPUT AMPLITUDE HIGH OR LOW Many times this can be cured by the adjustment of R6 as described in paragraph 5 14 If the correct amplitude cannot be obtained with this adjustment monitor the signal at Q6 C with an oscilloscope and set R6 to obt...

Page 68: ...n carefully monitor the output waveform Check for distortion or intermittent distortion small amplitude variations there should be none or spurious oscillations on the output signal Use a spectrum analyzer for this test see Table 4 2 step 3 These symptoms can be more readily traced than small frequency fluctuations 8 102 Almost any of the circuits can cause poor short term stability However the mo...

Page 69: ... 4 Q2 C 2 7 5 6 Note 8 Q2 E 06 2 Notes 4 and 5 Q3 B 2 7 5 6 Note 8 Q3 C 0 11 8 Note 4 Q3 E 2 4 4 9 Notes 4 and 6 Q4 B 0 6 3 Note 4 Q4 C 0 10 3 Note 4 Q4 E 0 5 6 Note 4 Q5 B 2 7 3 1 Note 8 Q5 C 0 11 8 Notes 8 and 9 Q5 E 2 8 2 6 Note 8 Q9 B 2 8 2 8 Note 8 9 Q9 C 5 1 11 8 Note 8 9 Q9 E 2 5 1 9 Note 8 NOTES 1 All voltages taken with 12V oscillator supply 2 Voltages are approximate and will vary slight...

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Page 71: ...Model 10811A B 63 ...

Page 72: ...Model 10811A B 64 Figure 8 15 Oven Controller Schematic Diagram ...

Page 73: ...Model 10811A B 65 ...

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