[Collins] KWM 1 power supply question - Mystery Jumper

[Dr. Gerald N. Johnson]

On 4/27/2010 1:20 PM, Greg Mijal wrote:
> Howdy:
>
> My recently acquired KWM 1 has been a tough one to mate to my home brew power supply and wondering if anyone knows the answer to this situation.
>
> Previously:
> All filaments light up ok and 260 vdc applied to the B plus line.  Current draw is correct per spec's but no receive, no nuthin'.
>
You need -65 also else its trying to transmit.

> Today: I spotted something in manual that does not appear anywhere else in the manual.
That is, the AC power supply schematic shows a jumper from pin 20 to 21 
on the connector.
>
In the schematic in the KWM-1 manual that I have in .pdf format, pins 19 
and 21 go to the two T/R relays for controling the external PA. Where 
they go has been inserted by hand, not originally part of the drawing. 
Pin 21 is grounded on receive by K2, and pin 19 is grounded on transmit 
by K1. I see no connections to either in any of the power supplies, in 
this manual 2nd ed 1 Nov 1957.

> I put the jumper in and the receive began to give the standard hissing sound.
> Looks like the jumper enabled something in the radio but the Collins manual doesn't seem to have an explanation.
> Can someone tell me what this jumper's electrical function is?  If I missed it and it's in the manual, what page do I go to?
> Thanks
> Greg
> WA7LYO
> Kinston NC
> ______________________________________________________________
>
This manual has page 17, which is mostly the second half of the voltage 
and resistance chart. I see nothing on receiver alignment. That's 
probably because the tuned circuits for the low level RF stage in the 
transmitter are the tune circuits for the receiver RF stage, V4. Only 
the receive IF stages are independent. L16 and T3 would probably be 
peaked on the S-meter while tuned to the crystal calibrator on any 
convenient band.

Receiver alignment is the worst thing to do until you have proper 
voltages and connections and are sure the receiver needs alignment. If 
there's a bad part or wrong voltage (like no bias voltage) trying to do 
an alignment will introduce more problems. Sure an alignment is simple, 
but it simply messes up good stuff.

Make sure the VOX gain isn't turned all the way CCW because that switch 
grounds PTT at full CCW and puts the rig in transmit mode. You don't 
want that without bias and PA plate voltage else the PA tube screens 
will draw excess current and probably will be damaged.

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