[Collins] KWM-2 + 312B-5

[Dr. Gerald N. Johnson]

Sounds as if he plugged it in with the power on. Not a good idea because 
there's supposed to be a jumper plug when the external VFO is not 
connected that changes the B+ and the heater wiring. Those are necessary 
to allow the VFO selector switch in the 312B-5 to pick which oscillator 
has power and which VFO dial is illuminated. From the early KWM-2 
schematic in the yellow book I can't see how it should blow one final 
since the final heaters are in parallel. There probably is an 
electrolytic being charged abruptly when the VFO is plugged in and 
something to check is whether the guide key on the plug is present and 
in the correct position. And when running on a 516F-2 all the tubes are 
in parallel running on a 6.3 volt AC supply.

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

On 9/3/2011 12:13 PM, Gary H. Harmon, Jr. wrote:
> A friend HAD a working KWM-2.  He plugged in an untested but clean original
> 312B-5.  There was a bang, an essence of fried something, loss of receiver
> audio and one final not lit.  Also, the cable from the 312B-5 was warm on
> the plug end.
>
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> Anyone been down this road?
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>
>
> 73,
>
>
>
> Gary H. Harmon, Jr. - K5JWK
>
> 6003 Archwood
>
> San Antonio, TX 78239-1504
>
> 210.657.1549h / 210.884.6926c
>
>
>
> "Retirement means every day is a Saturday, except Sunday".
>
>
>