[Collins] Clairvoyant KWM technician needed

[Dr. Gerald N. Johnson]

Lack of negative bias makes the KWM-2 operate weirdly. RF gain applies 
negative bias to the AVC line. See if turning down the RF gain causes 
the s-meter to rise.

Otherwise the low B+ seems to be missing, not getting to the 
transceiver. That will prevent any receiving and transmitting and relay 
operation.

Wrong polarity on the bias supply filter caps and an aged selenium 
rectifier that should be replaced by a silicon rectifier can kill the bias.

Time to trace voltages in the KWM-2 while hooked to the reworked 516F-2. 
And then check the voltages in the 516F-2 under load.

73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association.

On 12/29/2014 3:14 PM, John King via Collins wrote:
> Howdy Collins folks. I recently recapped my 516F-2 power supply and now I have a KWM2 problem. I have no audio from the receiver however when the KWM2 is first turned on the S meter rises to full right scale and the settles back down to normal minimum scale. That indicates to me that the receiver AVC is working, if nothing else is working. NO hiss, hum or any other noise from the speaker.
>
> Keying the PTT microphone produces no results and when the transmit switch is rotated to tune or lock the relay does not energize. That leads me to think that something common to the receiver audio and transmit circuitry might be involved in the problem.
>
> The 516F-2 is producing the required voltages, but he KWM 2 is not responding with anything but dial lights and lighted tubes. Anyone experienced a KWM 2 exhibiting those symptoms? Thanks for your input. 73, John, K5PGW
>