Heathkit AA-22, AA-29, AD-17, AD-19, AD-27 Troubleshooting Tips

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 Systems 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®). Don't use 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 slightly fast rotation (normal). CCW movement is too

• slow. (Contributed by John D'Amore, former Heath Field Service Manager.)

•

• Tone-arm won't clear raising pad, cuing lever operation jerky (see Figure AD-1): At first appearance,

it's the rising pad (location 1), however, check the pivot screw (2) to make sure it isn't 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 antiskating 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

bulletin #AD-110-1 doesn't help: Check C2. Place the banded end to ground. This is the outer foil and

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).

• Normal 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.

• Voltage 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 switches 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 stereo 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-Series 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.

AR-15

• 1 MHz oscillation at speaker 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, there's less of a tendency to jam when rotating dial.

AR-29

• No mute function: Check for leaky ZD-211.

AR-1500

• 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 output 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 collector 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 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 (X load on Q201s collector and a smaller RF signal (0.1 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.

=0.2975 ohms) to 10 pF (XC=1.487 kilohms). This reduces the

C-Series Automotive

CI-1079

• TI brand IC 443-7 may not always 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-linearity but won't open eye of

capacitor checker).

CO-2500

• Tachometer jitters: This is normal.

• 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 calibration, 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 ground 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.

GC-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 didn't use conductive 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 was 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 User's Group.)

General

• Interference may occur when the receiver is installed in the airplane, 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

connections 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 standard

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 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 if necessary.

GD-348

• Metal locator won't 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 cable doesn't correct). Placing a 0.02 uF ceramic disc (21-82) from "D" to "Y" on the audio board on series #01306 corrected.

• Won't 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-1162

• Receives but won't 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 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 won't blank when "E/R" pressed (step 11, pg. 82): Check IC-1111. Measure IC-1111 with an

IM-4100 and x10 probe (PKW-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 - 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 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 output 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 in the headphones. Reduce the volume setting and return the system to normal.

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