Heathkit-Troubleshooting-Tips 电路图 维修手册.pdf

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1、Heathkit Troubleshooting Tips AA-Series Amplifiers AA-22 SPST pushbutton power switch breaks down quite often. AA-29 Hum and noise audible w/volume turned up and covers taken off: This is normal (approx. 3mV 8 ohms measured with IM-48). AD-Series Audio Equipment AD-17, AD-19, AD-27, and Other System

2、s w/BSR-500 Changers Slow Speed and Slow Changer Action: Changer may even stop during change cycle. Check idler wheel height adjustment. Replace idler wheel if it has a hardened appearance. Clean idler wheel, pulley, platter, and changer mechanism with a non-lubricating solvent (Print-Kote). Dont us

3、e tuner contact cleaner as it usually contains silicon lubricant. Soak the bearing assembly in solvent (the assembly at the base of the spindle). Lightly oil this bearing assembly and the cam next to it after cleaning. Check speed with a strobe disk. Clockwise movement of the markers indicates a sli

4、ghtly fast rotation (normal). CCW movement is too slow. (Contributed by John DAmore, former Heath Field Service Manager.) Tone-arm wont clear raising pad, cuing lever operation jerky (see Figure AD-1): At first appearance, its the rising pad (location 1), however, check the pivot screw (2) to make s

5、ure it isnt too tight (this also has some effect on tone arm setdown). Tone-arm behaves normally halfway across LP, then sticks-playing the same groove over and over. Manually moving the tone arm inward about 1/2 fixes: This is due to grossly misadjusted anti-skate adjustment, causing the antiskatin

6、g spring to latch on to one or more protuberances. AD-17, AD-27 Stylus #236-202 NLA. Replace entire cartridge, #236-201. AD-27 Parts for the turntable can also be found in the AD-17 manual. AD-110 Excessive meter deflection, left channel, in record mode, w/recorder level turned up and service bullet

7、in #AD-110-1 doesnt help: Check C2. Place the banded end to ground. This is the outer foil and RadioFans.CN 收音机爱 好者资料库 provides shielding to prevent coupling from R66s bias cable to C2. Also, reposition the wires from R34 as far from the slide switch as possible (consider using shielded cable). Norm

8、al bias adjustment levels are about 25-28 Vrms at yellow wires of head. Dropping to about 16 Vrms improves high frequency response but causes distortion. The VU meters are used in record only-not playback. AJ-Series Tuners AJ-15 Motorboats with headphones plugged in: Check Q503-may be shorted. Volta

9、ge Measurements I.F. Voltages: Q305 - C = 10.5 V B = 2.5 V E = 1.7 V IC-301 - - 1 = 2.3 V - 2 = 2.3 V -10 = 9.8 V - 3 = 2.3 V - 4 = 2.3 V - 5 = 9.2 V IC-302 - - 1 = 2.3 V - 2 = 2.3 V -10 = 9.0 V - 4 = 2.3 V - 3 = 2.3 V - 5 = 6.0 V AJ-29 No muting action: Check for leaky ZD-211. AJ-33 DPDT slide swit

10、ches tend to open up or make intermittent contact: 50-50 chance of being cured w/contact cleaner. Also, the clamps holding the phenolic backs can be tightened. AJ-43D The effect of the SCA filter switch is very obvious: With this switch off, a high-pitched whistle can be heard in the background on s

11、tereo programs. AM Through AP-Series Audio Equipment AN-2016 Separation approximately 25 dB on Aux, Tape, and Tape monitor inputs: This is normal. The coupling capacitance between any disconnected unshielded input (or tape output) line to the rest of the wiring harness measures about 30 pF. AR-Serie

12、s Receivers AR-13 Motorboats at turn-off: Check for bad C17-C18 (both capacitors are in the same can). Dim stereo lamp: Check for open C16. AM oscillations: High end too sensitive-back off the RF and antenna trimmers to fix-will stay in specs. RadioFans.CN 收音机爱 好者资料库 AR-15 1 MHz oscillation at speak

13、er output: Check 201 or 202 for leakage. Or miswired transistor sockets. AM or FM dial cord jams: Try repositioning the respective tuning shaft bracket. As the tuning shaft is moved backwards, theres less of a tendency to jam when rotating dial. AR-29 No mute function: Check for leaky ZD-211. AR-150

14、0 Poor FM sensitivity: Check screw at coax ground lug on tuner assembly. Should be 6-32 x 1/4. If 6-32 x 3/8, the screw will short C802 (antenna trimmer) to ground. FM-IF DC voltage and relative RF levels: Set the FM signal to about 100 mV, modulated w/1 kHz, deviation ? kHz at 88 MHz. Adjust the ou

15、tput to give an approximate level (RF) of 0.4 V p-p at IC-201, pin 6. Use a 10 MHz scope or better and a low-capacitance X10 probe. This should show the following levels (dc-volts w/vtvm): Component DC Volts P-P RF (10.7 MHz) - - - IC201-3 1.5 V 0.1 IC201-6 10.7 0.4 R202 0.2 Q201 base 1.0 0.2 Q201 c

16、ollector 3.3 0.5 IC202-1 2.2 0.5 IC202-5 7.2 0.9 R210 0.3 IC203-1 2.2 0.3 IC203-5 7.0 2.5 T201-3 0.3 (audio) AGC and meter circuit levels. (Same setup as before.) Component DC Volts P-P RF (10.7 MHz) - - - Q204 base 0.7 0.5 Q204 collector 3.2 5.0 Q205 collector 12.3 7.0 R230, C228 -4.8 0 D201, D203

17、0 6 VAC (P-P) D201, D202 0.8 0 R225 to meter 0.14 0 Note: The previous two sets of measurements do not hold true for the AR-1500-A model. In the A model, C220 was changed from 0.05 uF (XC=0.2975 ohms) to 10 pF (XC=1.487 kilohms). This reduces the load on Q201s collector and a smaller RF signal (0.1

18、V P-P) is developed at Q204s base. A smaller AGC voltage is developed, so that the signal at Q201 collector is greater (about 1.5 V P-P). Thus, for the same level of incoming signal, the S-meter on the AR-1500A may indicate a lower level. C-Series Automotive CI-1079 TI brand IC 443-7 may not always

19、work here: Replace with Fairchild brand 443-7. CO-1015 Cal position shows 2 cycles for a brief period: Normal-can be speeded up somewhat by selecting D401 with a higher reverse resistance. Non-linear sweep: Check for leaky Q402. Non-linear sweep: Check C401 by substitution (bad one gives slight non-

20、linearity but wont open eye of capacitor checker). CO-2500 Tachometer jitters: This is normal. RadioFans.CN 收音机爱 好者资料库 Intermittent tachometer operation or no operation on motors other than 8 cylinders: Check for spread sockets on pins 1 and 8 of IC-203. If too heavy of wire is used during calibrati

21、on, the above may occur. TI brand IC 443-7 may not always work here: Replace with Fairchild brand 443-7. Different balance voltages with modified board-R136 from 47 ohms to 33 ohms. R123 from 22 kilohms to 47 kilohms. E-Series Educational Products ET-3400 Intermittent or no display: Check for good g

22、round at IC6, pin 6. G-Series Digital Clocks GB-1201 Count jumps a second or more when loading a number from function 5 to function 6: Replace the rotary switch, SW3. Be sure the insulation beneath it is installed. Note that the reset button must be set in function 5 prior to counting up a number. G

23、C-1092 One number brighter than others: Check D217 through D223 for leakage. No DC-upverter operation after modification: Replace Q201 with a 417-233 (2N3643). GC-1093 Improved dynamic range for automatic dimming circuit: Change R8 to 15 kilohms. Erratic operation: Make sure the customer didnt use c

24、onductive foam tape (supplied with some clock chips) for the padding between the crystal and the chip. Blue flare on AM or PM display: Check for leaky Q2-pulse must be about 11 V P-P. GD-Series Radio Control (Note: If I remember right, I got most of the following information from Bob Ellerton, who w

25、as a Heath Technical Consultant at the time and an RC enthusiast. Later, he was promoted to Factory Service Supervisor for the computer product line. Sometime after that, he took over as Manager of the Heath Users Group.) General Interference may occur when the receiver is installed in the airplane,

26、 but not in the shop: This may be due to metal-to-metal contact in the plane (push rods, etc.), rubbing due to vibration and generating electrical noise (see pg. 27 of GDA-1205-7 manual). Jittery Servos: This can be caused by the motor wiring. If 180-degree rotation occurs, try reversing the connect

27、ions to the motor before replacing. GDA-19-4 Servos are sluggish or have poor torque: The rack gears may be slightly out of tolerance. Also, observe left-right pairing of rack gears (for proper centering). Sluggish in one direction, will rotate nearly 180 degrees with servo simulator, centering stan

28、dard causes rotation in one extreme direction: All this is due to a dead monostable multivibrator. Check that the red wire to C8 is wired to the center tap and not the tap opposite the green wire. GD-Series Small Items GD-39 Q10 should be 0.25 V saturated. GD-48 Marginal operation: Clean the search

29、coil circuit board. Check C6 for leakage. IT-28 eye should open in 5 to 10 seconds. Oscillator is temperature sensitive and may not work in extreme cold or heat. GD-113 Intermittent oscillations in transmit: Tighten the hardware to the switching board-the bracket-strap and solder with braided shield

30、 if necessary. GD-348 Metal locator wont null properly, appears sensitive to the shaft: This may be due to improper capacitance on the spiral cable in the shaft. Try a capacitor-substitution box across various combinations of points A, D, Y, F, and G on the audio circuit board (if replacing the cabl

31、e doesnt correct). Placing a 0.02 uF ceramic disc (21-82) from D to Y on the audio board on series #01306 corrected. Wont null: Check signal voltage drops across R106 and R104. If no replacement search coil available, shunt R106 with cap in the 12-25 pF range (such as 20-77 mica) (24 pf). GD-1112/GD

32、-1162 Receives but wont transmit: Check Q1 (417-283). Can be either of two types-bases and collectors reversed-see pg 22 of assembly manual. GD-1150 Normal Operation: No load draws about 0.3 to 0.4 amperes. One inch of water with an object will draw 0.5 to 0.7 amps. GDA-1158-3/-4 60 Hz modulation of

33、 the 40 kHz/56 kHz carrier (amplitude): Replace Q102, Q103, and Q105 with 417- 118s (2N3393). The B-1097s that are supplied have a beta of 250 which appears to be the cause. GD-1185 Display wont blank when E/R pressed (step 11, pg. 82): Check IC-1111. Measure IC-1111 with an IM-4100 and x10 probe (P

34、KW-101) in the totalize mode. X10 atten will normally read 8 (E/R pressed), IC-1101 bad may read 16. Normal operating characteristics: IC-1106-3: freq=1,733 kHz to 1750 kHz; pulse count=8 pulses IC-1111-4: freq=108 kHz to 110 kHz; pulse count=8 pulses IC-1111-6: same as IC-1111-4 except for a + or -

35、 2 digit error on the count. GD-1187 Do not use an isolation transformer-touch switch may not work properly. General Audio Differential Power Amps Most Heath differential power amps (AA-1640, AR-1500, AA-29, etc.) can be initially (and safely) tested by removing the load and output transistors. The

36、drivers should reproduce a waveform as it normally would. If not, several expensive components have been saved from destruction. Tape Dubbing Test Tape Dubbing Test for New Audio Equipment: Plug a set of stereo headphones into the dubbing input. Activate the dubbing switch. Previous signal at the ou

37、tput should disappear. Turn the volume to near maximum. Tap the left and right headphone. A faint tap should be heard in the left and right speaker. Plug the headphones into the dubbing output. Feed a signal into a function switch-selected input (such as AM or FM). The signal should be faintly heard

38、 in the headphones. Reduce the volume setting and return the system to normal. GR-Series SWL and Ham Receivers GR-78 E-band dead on low end: (A) Replace Q301 with 417-167 (see above). (B) Change R304 to 1500 ohms. (C) Change R303 to 2200 ohms. (D) Swap L303 w/2200 ohms (prevents FMing when switching

39、 to C band). When aligning the unit, be sure the top cover is in place or the C, D, E, and F bands my break into parasitic oscillation. E-band extremely touchy in alignment of the oscillator-both high and low end: This can be caused by missing jumper wire from SW-301B, pin 8 to the circuit board sol

40、der run (L305, R303, etc). Align the E and F bands first: If Q301 does not function properly, it can be replaced without having to re- align the entire unit. Do not attempt alignment without the top cover or the bottom switch-board shield, or without the switch shaft installed. All of these will aff

41、ect the local oscillator frequency. E and F bands dead on the low end: This may be due to a low gain-bandwidth product of Q301, so that with the lower Q of C305-L305-R303 (on E) and C306, L306, R304 (on F) when tuned to their respective low ends prevents enough positive feedback to maintain oscillat

42、ion. To cure, try removing R303 and replacing the 2200 ohm at R304 with a 5600 ohm resistor. If this doesnt work, try the unauthorized modification shown with the illustration, above. GR-110 TI brand 443-7 will not always work here. Use Fairchild. Q101 and Q102 will measure 4 volts on gate two w/33

43、kilohm resistors at R102 and R105 (used to be 15 kilohms). Priority oscillator wont catch channel 0 signal: Replace IC-105. GR-Series Television GR-104 Faint vertical bars: Check C232. High voltage drops with the brightness turned up-similar to low horizontal drive: Check for open L201. GR-300, 400,

44、 and 500 No AFT: The AFT assembly may be installed backwards. AFC erratic; picture loses sync, picture polarity reverses: Problem occurs when changing channels. Corrects itself when turning the TV off or on: Check L327-should be to tuned to 2nd peak from the top. GR-900 Luminance board #85-365-6 sam

45、e as #85-365-9 except for Q254 in the dot generator and can be interchanged for most purposes. No 3.58 MHz from the oscillator circuit board but the transformers and active components are okay: Check for an open D406. Loss of interlace after 1/2 to 2 minutes of operation-sides pull in: Waveform at p

46、in 2 of horizontal oscillator board about 2 V P-P sawtooth. Check for open L552. Boards check okay for any kind of problem, wiring appears correct: Check the wiring harness at the breakouts. Now and then, two or more wires will pinch together (possibly at time of harness construction). No dots: Chec

47、k for leaky C701. Intermittent horizontal jitter: Check C563. No AFT-adjusts okay: Check for reversed black and red wires on red chassis plug. GR-2000 Preset tuning controls unable to adjust from low end of Lo-VHF to high end of Lo-VHF (ditto for Hi- VHF): Check collector voltages of Q201 through Q2

48、16. Only one should be high. If not, the cathode voltages of D249 through D264 cannot be properly controlled by any single tuning potentiometer. Outside of bad solder connections or open transistors, check for open/defective transistor sockets. GR-2001 Clock oscillation: (1) Put ferrite bead on Q53 collector. (2) Change C114 to 0.001 on memory board of programmer. H-Series Computers H8 Check for shorts between runs on the mother board. Most common problem. +/-18 V supply failure next most