[Collins] KWM-2 + 312B-5

[Dr. Gerald N. Johnson]

Foot in mouth. Its a 9 pin miniature plug. Same as used for the noise 
blanker next to the VFO socket which has a shorting plug in it. Sure it 
was in the right socket? Some of the pins are the same and some are 
wildly different. Also check for missing pins on the miniature plug.

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

On 9/4/2011 12:03 AM, Dr. Gerald N. Johnson wrote:
> 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.
>>
>>
>>
>> Anyone been down this road?
>>
>>
>>
>> 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".
>>
>>
>>
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