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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.
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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
C=0.2975 ohms) to 10 pF (X C=1.487 kilohms). This reduces the
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.
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.
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- Microphonics on receive calibrate: This is normal if they occur when the unit is jarred.
- 7 MHz and 14 MHz (40 & 20 meters) bands dips instead of peaks (rcv & xmit): This is the combined
effects of L702 through L705 and/or L802 through L805. Selecting coils for the offending board may help.
In one case, the culprits were the 21 MHz (15 meter) coils.
- Low power output, all bands, worse on 10 meters: Try replacing the finals (V8, V9) with GE-brand
tubes. RCA-brand tubes appear to be the cause. Also, sub V7.
- Low power output at 40 meters: Check C703, C704, C802, and C803. May be out of tolerance.
- Oscillates on 15 and 10 meters: Be sure that the neutralization wire from the preselector isn't shorted to
ground. Check for good grounds on the shields of the drivers.
- Relay chatter in VOX mode: Replace the two wht/rd/rd wires to R213/R214 with shielded cable. Ground
the shields near R213/R214.
- High plate current, no RF power out on some bands--receive okay: Check for broken taps on L904.
HW-2021
An anecdote: In 1979 I was promoted from Senior Technician to Service Technical Writer and was transferred from
Omaha to St. Joseph, Michigan. There was kind of a fire going on and I was required to write service manuals on the
newly released H19 terminal and H89 computer.
After I finished them, my boss, Frank K., assigned me to write a manual on a new Heath 2-meter handy-talky. (I no
longer remember what the model number was.) Frank advised me to use the HW-2021 service manual as a guide. I,
with my vast experience of writing two service manuals, pointed out to him that while the HW-2021 manual was
good, I found it lacking. I went on at great length describing in detail how I could write a better manual.
When I finally stopped to catch my breath, Frank quietly said "I wrote that manual."
Meanwhile, our typist/proofreader/illustrator, Fran, was doing her damnedest not to bust a gut.
At the time, I didn't realize that I was still new and that Frank had many more years of servicing, writing, and editing
experience than I did.
Frank was okay, though. You begin to realize you have a good boss when you work for him for 13 years and even
turn down job offers from other departments.
- TVI: May be due to 45 MHz radiation. Disconnect the brown wire from hole "U" on the main circuit board
and reconnect at the hole near the emitter of Q15.
- The collector V RF of Q24 is normally lower than that of the collector of Q23. Other stages show gain.
- Low power output: Make sure that the P.A. transistor is mounted close to the board.
- Offset switch damage occurs easily, check while servicing.
- Quieting is normally best about 1 kHz below minimum THD.
- Oscillator won't net: Change C57 to 56 pf. Also try changing the netting capacitors or the bias resistors to
the varactor diode (in extreme conditions).
- Receive oscillations: Check for a well-grounded clip at the antenna terminal. Build up a layer of solder on
the foil-side screw-hole rings on the circuit board to insure a good ground connection to the metalized
plastic case. To give a better ground contact for the antenna, place the flat washer on the antenna jack on
the inside of the case.
- Batteries won't charge: Check the spring assemblies in the battery pack. These can protrude and short to
the case.
- Transmitter alignment: Be sure the power supply voltage to the transmitter circuits are the correct levels.
Either use the battery pack or increase the external DC supply to the point that equals normal battery pack
operation. Otherwise, you'll get erratic results.
- 1 mH chokes (#45-80) are heat sensitive and can easily be destroyed.
- Erratic oscillator: Look for the 1 mH in the ??? circuit rather than the circuit of Q???.
HW-2026
If I remember right, the HW-2026 caused some serious cross-talk problems in cities with repeaters that were close
together. At the time, the Heath engineers could not solve the problem (short of totally redesigning the unit). So the
Heath company contacted all their customers to recall the kit. The deal was this: If the kit wasn't built yet, Heath
would refund the customer's money plus pay an extra $25. If the kit was already assembled, Heath would refund the
money plus pay the customer $50 (big bucks in those days). If the customer chose not to return the kit, Heath would
not provide service or any other support.
Amazingly, many customers chose to keep the radio.
- Its spurs were -40db @ +/- 2 MHz of the carrier. The HW-2036 is -70db at +/- 20 MHz of the carrier.
