{Collins} Fwd: RE: KWM-2A problems and tubelore question



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From: "Ian" <ianwebb5@xxxxxxxxxxx>
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Subject: RE: {Collins} KWM-2A problems and tubelore question
Date: Sun, 24 Oct 2004 14:02:32 -0700
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I guess at least I should try to point a fellow electronics teacher in the
right direction.  <grin>

Before you do anything else I suggest loosening the cans that cover the band
switch and the coils and do whatever cleaning is required and then make sure
the can is well grounded to the chassis when tightened back down.  I've
found over the years that to be a problem with all of the S-Line gear.

If you wish to go a step further you can remove the shaft that goes through
the cans and pull it out through the hole at the back chassis apron.  Look
carefully and keep in mind how to properly orient it and the switch wafers
when you put it back in.  While it's out do some cleaning on the wafers with
a very small amount of something like Caig's contact cleaner.  

Then you could remove the cans entirely and clean and shine the mating
surfaces and reform the push stock that goes between the can and the chassis
to improve the contact.

You may also have to pop the trimmers and clean and make sure that the
trimmer hasn't been destroyed by trying to force it to turn before making
sure that it isn't frozen.  I've cleaned just about every trimmer on several
KWM-2s and often they have frozen over time and if forced to turn will have
problems and possibly destroy the trimmers.

Good luck!

Ian, K6SDE
Silicon Valley 

-----Original Message-----
From: collins-bounce@xxxxxxxxxxxxxxxxxxxxx
[mailto:collins-bounce@xxxxxxxxxxxxxxxxxxxxx] On Behalf Of Robert Stewart
Sent: Sunday, October 24, 2004 11:06 AM
To: collins@xxxxxxxxxxxxx
Subject: {Collins} KWM-2A problems and tubelore question

Hello to the group.  I have returned to Ham Radio after an almost 16 year
absence and decided to get the radios I wanted the first time: Collins.  Of
course, I bought them from ebay with the predictable result: one works
pretty good and the other has problems.  

My background, I used to have an Advanced class license, and I taught
electronics in the Air Force, so I have a fair amount of technical skills.
Plus, I built several Heathkit rigs and did some homebrewing back in the
day.  I've returned to Ham Radio with an Extra this time.

My questions;

My KWM-2A has a self oscillation somewhere.  When I tune Z5, its frequency
changes.  Any ideas where to start?

Next: in section 4.5.1.2 of the instruction book, it says to disable the
screen circuit before proceeding with the 455-KC IF alignment.  Is this
really necessary, or is it sufficient to simply bias the finals past cutoff?
I'm guessing that the real purpose behind removing the screen voltage is to
just prevent overheating the finals while messing with T1 and C54.  What's
SOP here?

Finally, I've forgotten most of my "tubelore".  I also have a KWM-2 which
works pretty good.  But, both rigs have one tube (different on each) that
glows blue.  In one, it's V13.  In the other, it's V3.  Swapping both out
doesn't fix the problem.  Is this a sign of some voltage or drive problem
that I need to address.

Thanks in advance,

Bob, AE6RV
Sponsored by the Collins Collectors Association http://www.collinsradio.org
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Sponsored by the Collins Collectors Association http://www.collinsradio.org
Nets: Tues: 3.805 Mc-2000 Central / Thur: 3.875 Mc-2000 Central
Fri: 3.895 Mc-2000 Pacific / Sun: 14.263 Mc-2000 UTC
1st Wed (of the month) AM Net 3.880 Mc-2000 local (ET, CT, MT, PT)
Sun AM Net: 29.050 Mc-1200 Central






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