| Symptom: |
Unit will not turn on. |
| Probable
Causes: |
1) Cracked solder
joints at battery connections. 2) Cracked solder at jumpers to VR
unit. 3) Bad flex cable. 4) Problems on logic unit. |
| Cure: |
Check the resistance
between the "E" and "-" terminals on the bottom
of the radio. Should be 0 ohms. Check the jumpers on the VR unit for
cracked solder joints and repair as needed. If OK, verify proper
logic board voltages as per the service manual. Failure here may
mean a bad flex cable or faulty CPU crystal (check pin 29 of CPU for
oscillation). |
|
|
| Symptom: |
Unit runs off internal
battery, but not external DC. |
| Probable
Causes: |
1) Faulty D9 diode on
PRT unit. 2) Faulty DC jack. |
| Cure: |
Replace faulty D9 diode
and/or faulty DC jack. |
|
|
| Symptom: |
Unit runs off external
DC, but not from internal battery. |
| Probable
Cause: |
Faulty D15 diode on the
main unit. |
| Cure: |
Replace faulty D15
diode. |
|
|
| Symptom: |
Internal or external
battery charging problems. |
| Probable
Causes: |
1) Failure on PRT unit.
2) Missing components. |
| Cure: |
Check for proper
voltages on PRT unit. Start at D2 or D8 diodes and troubleshoot from
there. Check for missing components under adhesive insulator. |
|
|
| Symptom: |
Unit has display but no
RX/TX at all. |
| Probable
Cause: |
PLL unlock. |
| Cure: |
Remove the main unit
and check the +5 V, +5S, PLL STB, DATA, CK lines. |
| Remarks: |
Look for damage from a
poorly executed out-of-band modification. |
|
|
| Symptom: |
No TX output. |
| Probable
Causes: |
1) Loose antenna
connector and/or center conductor jumper wire. 2) Faulty driver
and/or PA module. |
| Cure: |
Check antenna connector
for tightness and resolder cracked solder joints as needed. If OK,
check the APC and PDI voltages to the power module. If OK check the
gain across the PA and driver: driver is approx. 10 dB, PA is
approx. 40 dB. There should be very little loss between the power
module and antenna jack. |
|
|
| Symptom: |
No deviation. TX output
is OK. |
| Probable
Causes: |
1) Bad mic element. 2)
Faulty flex cable. 3) Broken chip resistor on main board. |
| Cure: |
If unit works OK with
external microphone, check for bad flex cable or internal mic
element. If unit does not work with external mic, check for 75 mV
p-p audio to mic amp. If present, check for a broken chip resistor
on the main board where the shield screws into the upper right
corner of the main board (top view). |
|
|
| Symptom: |
No RX, or low RX
sensitivity. |
| Probable
Causes: |
1) Misalignment. 2) Low
R+5V. 3) Faulty D7 diode on main unit. |
| Cure: |
Make sure unit has not
been misaligned. Check the R+5V for proper voltage in RX (5 Volts).
If OK, check D7 diode on main unit and replace if needed. If unit
still does not operate, check the gain of the RF stages:
* RF amp has 18 dB gain
* Mixer 30.875 MHz LO level is very low, about equal to antenna
input levels.
* First mixer has approx. 15 dB of gain.
* No loss through the filters.
* Some loss through R6 resistor.
If the above stages are OK, check the detector unit for proper
operation. |
|
|
| Symptom: |
No audio, but
unit seems to be receiving signals. |
| Probable
Causes: |
1) Bad speaker. 2) Bad
flex cable. 3) Burned foil trace. 4) Broken jumpers to VR unit. |
| Cure: |
Disconnect speaker and
check for presence of audio on speaker wires. If present, replace
defective speaker. Trace audio at flex cable. Replace flex cable if
needed. Check for a burned foil trace at ground of external speaker
and repair as needed. This is caused by user plugging in external
power to speaker jack. Check for cracked joints at jumpers to VR
unit and repair as needed. If all else is OK, check the output
through the AF unit: should be 5 Volts p-p at full volume level. If
it's not there, check for an output signal on the DET OUT line of
the DET unit. |
| Remarks: |
If the audio is very
low, check for a faulty C20 tantalum capacitor on the main unit and
replace as needed. |
|
|
| Symptom: |
Intermittent operation
of some keypad functions. |
| Probable
Cause: |
Cracked solder to the
keypad board. |
| Cure: |
Inspect keypad board
solder connection for cracks and repair as needed. |
|
|
| Symptom: |
Display shifting or
rolling. |
| Probable
Cause: |
Faulty CPU clock
oscillator. |
| Cure: |
Check CPU clock
oscillator for proper level. Replace crystal if needed. |
|
|
| Symptom: |
Channel knob shift down
or frequency change does not operate. |
| Probable
Cause: |
Open ground to VR
board. |
| Cure: |
Check VR board for
proper ground. Also check for cracked solder joints at VR jumpers. |
