Symptom:
On early versions of the TS-950 series (below serial number 106xxx) a hum might be heard when the MONI function is active and headphones are connected to the PHONE jack. No hum is experienced when the MONI circuit is OFF
Cause:
This noise can only be found in the monitor circuit itself and not on the transmitted signal. We have found that the VCO shield cover for the PLL unit might be contacting the shield plate for the filter unit. This physical contact can allow a slight amount of vibration to be felt in the sub-receiver section. This vibration, combined with too much gain in the sub-receiver section contributes to the hum.
Parts required:
Qty Description Kenwood Part No. Circuit description
4 Low profile PLL Unit cover screws N35-2640-05 NA
Procedure:
- On the IF unit (X48-3060-00) adjust VR-1 to the point the audio output just decreases when the MONI circuit is activated.
- Replace the screws on the VCO unit shield case with the new low profile screws.
Time required for this modification is 15 minutes or less.
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