{Collins} Re: KWM-2/516F-2 voltage question - update

   thanks for the specific info. Exactly what I was looking for.

Last night I did some more checking. I retested all the tubes for
emission, shorts and leakage and all is OK. I then tested the power
supply separately by jumping the AC switch pins and I got the required
voltages at the other pins, albeit, somewhat high on the B+. I got
7.0 volts AC for the filaments. I also checked the cable for the solid
wire ground issues mentioned before. So, at this point, it's pointing
back to the M-2. This older M-2 has not had the eletrolytic's changed
yet except for C-102 which I did previously, so I'll change them out
next, needs to be done!

Tom Laird WC9M
Moline, IL.

-----Original Message-----


First I suggest that you go to the Collins Collectors website and down =
the schematic and manual for the 516F-2. It lists the voltages used with =

the KWM-2 Here's the voltages that should be available. Keep in mind =
these values apply to light load conditions such as receive and to full =
conditions such as transmit.

Heater...........6.3VAC =3D/- 0.3V - measure between pin 8 and pin 3 of =
Low B+...........275VDC  nominal - measure between pin 1 and pin 3 of P1
Transmit ........250VDC

High B+..........800VDC  nominal - measure between pin 2 and pin 3 of P1

Bias voltage...-55 to -80VDC adjustable - measure between pin 4 and pin =
of P1

P1 connections:
#1 =3D Low B+ (red/white wire)
#2 =3D High B+ (black/white wire)
#3 =3D Ground
#4 =3D Bias (brown/white wire)
#5 =3D AC Switched (gray/white wire)
#6 =3D NC
#7 =3D AC Common (orange/white wire)
#8 =3D 6.3 Filament (violate/white wire)
#9 =3D 6.3 Filament (blue/white wire)
#10 =3D Ground (green/white wire)
#11 =3D Ground (yellow/white wire)

*NOTE: pins #8 and #9 are connected together, therefore 6.3VAC is =
between either of these and ground

Also make sure that the braid or shield of the cable from the power =
is connected to ground inside of the power supply. There have been cases =

where this ground was broken and thus pin #3 was not effectively =
to ground.


> How and where do you measure the power supply voltages on a KWM-2. =
What =3D
> I'm getting at is;
> what's your preferred method and why? I'm assuming that most would =
take =3D
> measurements somewhere
> in the M-2 and not necessarily start in the 516F-2. Another specific, =
I =3D
> want to know is how and
> where do you measure plate voltage during transmit? Screen, bias,
> filament etc.....
> What happened last week was, I purchased another M-2 and was checking
> the neutralization when
> the radio basically "flat lined"; it was receiving and transmitting =
> that point, although
> not transmitting well. I turns on and the lights come on, looks like =
> filaments are on, the
> s-meter rises, but stays near the top, but not pegged. I have no rx =
> the relays do nothing.
> The mode switch makes no difference where it's at, the S-meter just
> stays near the top of the
> scale. I rechecked the tubes and the relays (all three) seemed to be
> de-energized and not stuck
> on. I removed the finals and driver and re-checked and still no dice.
> I am now suspecting a power supply issue. Any other ideas are =
> Tom Laird WC9M

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