| Symptom: |
"Rushing
water" or "aurora" sound in FM receive audio. SSB
sounds raspy and distorted. |
| Probable
Causes: |
1) Bad plastic trimmer
capacitors on HPL unit. 2) Old, dried out electrolytic capacitor C2
on HPL unit is allowing regulator to oscillate. |
| Cure: |
Replace faulty trimmer
capacitors C16 and C78 on HPL unit with ceramic versions of
identical values. Replace C2 electrolytic capacitor. |
| Remarks: |
To allow proper
alignment of ceramic trimmers, reverse values of C16 and C78: Make
C16=12 pf, and C78=6 pf. |
|
|
| Symptom: |
Frequency instability. |
| Probable
Causes: |
1) Bad plastic trimmer
capacitors in HPL unit. 2) Cracked solder at IC2 regulator on HPL
unit. |
| Cure: |
Replace trimmer
capacitors as stated in the previous paragraph. Resolder cracked
solder joints at regulator. |
|
|
| Symptom: |
No RX/TX, or no RX/TX
when unit warms up. Unit may have dead spots in tuning range.
Inspection reveals that the HPL loop is unlocked. Trimmer capacitors
on HPL unit have already been replaced. |
| Probable
Causes: |
Bad C9 capacitor on HPL
unit. |
| Cure: |
Replace C9 (1 µF,
50-volt) BP capacitor on HPL unit. |
|
|
| Symptom: |
No frequency display,
only decimal points. Problem may be intermittent or temperature
related. |
| Probable
Cause: |
Display DC-DC converter
has noisy output. |
| Cure: |
Replace all of the
following dried-out electrolytic capacitors on the display unit: C3,
C6, C7, C8, C9, C10, C11, and C14. (These capacitors are blue when
they are new. Capacitors that have turned gray or brown are old and
dried-out.) |
| Remarks: |
While servicing the
DC-DC converter section, look for cracked solder joints as this
section of the radio tends to run hot. Also, we recommend
reprogramming the RAM card after servicing the DC-DC section. |
|
|
| Symptom: |
Erratic display i.e.,
frequency listed will be out of the normal operating range of the
radio. Rotating the VFO knob may cause strange characters to appear
in the display. Cycling the power switch a few times may restore
operation temporarily. |
| Probable
Causes: |
1) Cracked solder on
RAM unit is causing logic errors. 2) Program in RAM unit is
corrupted. 3) IC21 regulator chip on logic unit is producing noise
or oscillating. |
| Cure: |
Replace filter
capacitors C11, C26, and C26 on logic unit if they appear overheated
or dried out. Resolder cracked solder joints at J1 and J2 connectors
on RAM unit, then reprogram. If this does not help, substitute RAM
unit with a known good one. If the RAM unit does not cure the
problem, there may be noise from the DC-DC converter causing the
logic unit to glitch. Follow instructions for the previous problem. |
| Remarks: |
While servicing the
DC-DC converter section, look for cracked solder joints as this
section of the radio tends to run hot. Also, we recommend
reprogramming the RAM card after servicing the DC-DC section. |
|
|
| Symptom: |
Intermittent RX/TX. May
have dead spots in tuning range. |
| Probable
Causes: |
Bad data to HPL unit. |
| Cure: |
Resolder solder joints
at J11 connector on logic unit. Resolder other suspected poor joints
on logic unit. If this does not help, there may be a problem with
RAM unit or associated circuitry. (See previous listed repair.) |
|
|
| Symptom: |
CPU noise in audio. |
| Probable
Causes: |
Poor ground on display
unit. |
| Cure: |
Tighten the screws that
hold down the display unit PCB. If this does not help, install a
plastic-coated metal shield over the display unit. This type of
shield is available through our parts department. |
|
|
| Symptom: |
Loud, high
pitched-squeal emanates from inside radio. |
| Probable
Causes: |
DC-DC converter
transformer has a loose core. |
| Cure: |
Replace T1 (T0-9)
transformer on the display unit. |
|
|
| Symptom: |
Very Low RX
sensitivity. |
| Probable
Causes: |
Bad Q7 FET on YGR unit. |
| Cure: |
Replace bad Q7 FET
(2SK125). |
|
|
| Symptom: |
No RX. Investigation
reveals that T/R relay (RL1) on filter unit does not release in
receive mode. |
| Probable
Causes: |
Leaky Q39 transistor on
main unit. |
| Cure: |
Replace leaky Q39
transistor (2SC2785). |
|
|
| Symptom: |
Drastic change in audio
frequency response between USB and LSB., i.e. USB audio has too much
bass while LSB audio has too much treble. TX frequency response is
also poor. |
| Probable
Causes: |
Misadjustment of the
BFO or a faulty crystal filter. |
| Cure: |
Realign the BFO. If
this doesn't help, then the problem is most likely a bad FI-1 filter
on the main unit (10M24D4). |
|
|
| Symptom: |
VFO tuning is erratic.
Sometimes frequency doesn't increment steadily when VFO knob is
turned. |
| Probable
Causes: |
Dirty rotary encoder. |
| Cure: |
Remove white plastic
cover from back of rotary encoder and spray-clean the carbon track
with Blue Shower solvent. Spin VFO knob vigorously while spraying. |
| Remarks: |
Do not let solvent
saturate the display unit or allow it to come into contact with the
plastic display lens. Stuff a paper towel between the rotary encoder
and display unit to catch spray run-off. |
|
|
| Symptom: |
In 271H, low TX power
output with high current draw from the power supply. |
| Probable
Causes: |
Bad C28 SMD capacitor
on PA unit. |
| Cure: |
Replace C28 capacitor. |
