Re: {Collins} KWM2-A Low Power Output and Erratic Grid Current



This has been my experience with my grandfather's old KWM-2, which I'm trying to get on the air. This unit was in storage for a very long time. I spritzed the contacts I could reach with some DeOxIt, and that seemed to make receiving very clear. I probably need to do some more disassembly in order to reach some of the other pots and switches.

I am somewhat worried about damaging the unit, but I will try to reseat some of the tube sockets.

I found that using a small dry paintbrush was great for brushing out dust and particles from the metal on the bottom, and that let me get around the tubes. The mechanics seem to be in superb shape. I expect oxidation and crud to be the only problem with the unit.

So far, I do not have a microphone. My friend and I tried to CW QSO, but we weren't heard during our trial run.

	Is this thing supposed to get space-heater hot?


On 8/12/13 1:28 PM, Steve Berman wrote:
Torrey, I agree with what Buck mentioned re the ceramic trimmer caps.
If the rig has been in long storage, I would also go through the
switches, pots and relay contacts.  Over time, the switch and relay
contacts will oxidize, resulting in high resistance connections.
That's a large cause if erratic meter readings on all of the S/Line
rigs. Let us know what you find. 73, Steve,  N6HK

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

From: Torrey Mitchell Sent: 12 Aug 2013 16:15:26 GMT To:
n6hk@xxxxxxxxxxx Cc: Collins@xxxxxxxxxxxxx Subject: {Collins} KWM2-A
Low Power Output and Erratic Grid Current

After several years I have resurrected my RE KWM2-A (SN 18xxx).  It's
been a bumpy road.  But I am back on the air.well sort of.  Receiver
is excellent.



However, grid drive is erratic and power output uniformly low.40-50%
reduced at best.  Sometimes when I turn it on, there is lots of grid
current requiring me to back off on the mic control to 9 o'clock to
get a peak. Other times when I turn it on, the grid current is low
from 0 to 120 ma.like this morning.



Yesterday I had a couple of QSO's with good signal quality reports.
PEP output then at 50-60 watts PEP represents the best I can get.
That was on 20m, but 80-15m behave the same way.



I've made tube substitutions for the driver and final tubes without
change. I've even done the old trick of losing then tightening all
the tube socket screws to overcome corrosion of the ground path.



I'm looking for suggestions to troubleshoot this problem.  I really
want to get it up and fully running.after 6 years.



Thanks and best 73,



Torrey N9PY

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Drew from Zhrodague
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Drew from Zhrodague
kitchen biochemical warfare
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