[Collins] RE: Collins digest, Vol 4 #184 - 5 msgs
Leslie Groberman
[email protected]
Sat, 12 Jul 2003 16:30:55 -0700
More on good alignment of R388.
The IF is 500kc, so the easiest way of getting good alignment is to put a
counter on the IF out. Then tweak the IF adjustments with as low a signal as
possible with an input that results in the IF signal being 500kc +/- 100 hz.
Use a scope as a signal strength meter.
When you have gotten all you can out of the IF (you may have to go over the
IF 3 or 4 times) then you can move onto the rest of the radio. The crystal
filter should come in right on the button, and the BFO can easily be set for
the middle of the range.(that is, the capacitor that tunes the BFO is pretty
close to mid-range)
The rest of the radio should go along without any surprises. Just peak the
individual trimmers for the top end of the appropriate band.
When all is said and done, it helps to plot amplitude versus frequency of
the radio (this is easy with a counter on the IF out) and you can see the
IF, what the crystal filter does and otherwise have some perverse fun with a
50 year old hulk that should come in at less than 1uv for 10db Sinad.
It goes without saying that the ONLY problem with the radio is the
alignment.
Les Groberman / VE7BLP
-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of
[email protected]
Sent: July 12, 2003 1:02 AM
To: [email protected]
Subject: Collins digest, Vol 4 #184 - 5 msgs
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Today's Topics:
1. RE: Need Advice - KWM 2A Transmitter Problems (AI2Q)
2. Re: Need Advice - KWM 2A Transmitter Problems (Dr. Gerald N. Johnson,
electrical engineer)
3. Re: Need Advice - KWM 2A Transmitter Problems (Jim Brannigan)
4. Re: Need Advice - KWM 2A Transmitter Problems (Glen Zook)
5. More 310B-1 coils (W0YG Charlie Summers)
--__--__--
Message: 1
Reply-To: <[email protected]>
From: "AI2Q" <[email protected]>
To: "'John Page'" <[email protected]>, <[email protected]>,
<[email protected]>
Subject: RE: [Collins] Need Advice - KWM 2A Transmitter Problems
Date: Fri, 11 Jul 2003 08:39:07 -0400
Paul, start by checking all of the set's tubes. Next, check the power supply
DC voltages, and be sure that the filament voltages are correct as well.
Then clean all the switches and controls. Then do an alignment. That will
help you zero-in on the errant stage/s. I used to repair them in the US Army
(they were designated RT-718s).
Vy 73, AI2Q, Alex in Kennebunk, Maine
http://users.adelphia.net/~alexmm/ai2q.htm
.-.-.
---Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of John Page
Sent: Thursday, July 10, 2003 11:07 PM
To: [email protected]; [email protected]
Subject: Re: [Collins] Need Advice - KWM 2A Transmitter Problems
There are many things that could cause this. But the easiest and cheapest to
do first is to CLEAN the bandswitch. Might as well clean the rest of them
while you are in there. Now try it and tell us how it did. John
John Page K4KWM
Hollow State since 1953
(ex W8PKU,N8BLB,NA8O)
>From: [email protected]
>To: [email protected]
>Subject: [Collins] Need Advice - KWM 2A Transmitter Problems
>Date: Thu, 10 Jul 2003 21:16:30 -0500
>
>I recently purchased a WE KWM 2A (circa 1968) that appears to have
>transmitter
>problems on some bands. It appears to be working somewhat on 75 and 40
>meters but the other bands won't load up at all. It makes no difference
>if I tune
>it up into a Laboratory 50 Ohm dummy load or into an antenna, the
>behavior is
>the same.
>
>Here are my observations:
>
>75 & 40 Meters
>
>Tunes up and loads OK with slightly lower plate current and RF output
>than the
>book values in the manual. RX seems to be OK.
>
>20 Meters
>
>No grid current indication in tune position. RX noise peaks but no plate
>current
>thus unable to dip plate or measure any RF output.
>
>15 Meters
>
>Grid current & exciter peak very touchy. Was finally able to get tuned
>similar to
>75 & 40 Meter behavior.
>
>10 Meters
>
>Same characteristics as 20 Meters unable to get it to load up
>
>Prehaps those of you with specific Collins experience, especially
>"hollow state"
>knowledge of this rig can give me some ideas of where and what to look at
>to
>get this repaired. I'd also appreciate any insight into who might
>specialize in
>KWM 2A repair & alignment. I'll be anxiously awaiting your replies .....
>
>Paul - K8PD
>Noblesville, IN
>
>
>
--__--__--
Message: 2
Date: Fri, 11 Jul 2003 08:23:13 -0500
From: "Dr. Gerald N. Johnson, electrical engineer" <[email protected]>
Reply-To: [email protected]
Organization: Gerald N. Johnson
To: [email protected]
Cc: [email protected]
Subject: Re: [Collins] Need Advice - KWM 2A Transmitter Problems
After cleaning all the bandswitch contacts with a quarter drop each of
DeoxIT, you need to attack the Erie 8-50 trimmers for each band switch
position. They have a tendency for their internal connection from shaft
to terminal (accessible on the bottom side) to go open. DeoxIT should
work there too, but the necessary twisting to break down the oxide will
destroy the alignment. It is also possible that the ceramic may be stuck
making rotation difficult of impossible. Then replacement may be
necessary.
I'm NOT a fan of test by alignment. Some of the slug tuned coils
especially are fragile and the fiberglass has roughened the threads over
the decades and one too many turns locks the slug and then breaks the
coil form loose (if the epoxy hasn't already failed from old age) cause
far more problems than if the coil was just a little off perfect
alignment.
73, Jerry, K0CQ, Technical Advisor to the CRA.
--
Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.
--__--__--
Message: 3
Date: Fri, 11 Jul 2003 10:49:58 -0400
From: Jim Brannigan <[email protected]>
Subject: Re: [Collins] Need Advice - KWM 2A Transmitter Problems
To: [email protected], [email protected]
Cc: [email protected]
If the trimmer won't tune the circuit or has a limited range (there should
be two peaks 180 degrees apart) then they are a candidate for repair or
replacement.
I've had success repairing stuck trimmers. Remove the small retaining ring
on the bottom of the trimmer. VERY carefully take it apart and clean. That
will usually do it. On a few, I used a very small amount of rubber cement
to hold the stator in place.
Jim
> After cleaning all the bandswitch contacts with a quarter drop each of
> DeoxIT, you need to attack the Erie 8-50 trimmers for each band switch
> position. They have a tendency for their internal connection from shaft
> to terminal (accessible on the bottom side) to go open. DeoxIT should
> work there too, but the necessary twisting to break down the oxide will
> destroy the alignment. It is also possible that the ceramic may be stuck
> making rotation difficult of impossible. Then replacement may be
> necessary.
>
> I'm NOT a fan of test by alignment. Some of the slug tuned coils
> especially are fragile and the fiberglass has roughened the threads over
> the decades and one too many turns locks the slug and then breaks the
> coil form loose (if the epoxy hasn't already failed from old age) cause
> far more problems than if the coil was just a little off perfect
> alignment.
>
> 73, Jerry, K0CQ, Technical Advisor to the CRA.
--__--__--
Message: 4
Date: Fri, 11 Jul 2003 08:43:09 -0700 (PDT)
From: Glen Zook <[email protected]>
Subject: Re: [Collins] Need Advice - KWM 2A Transmitter Problems
To: [email protected], [email protected]
Cc: [email protected]
Actually, the small ceramic trimmers are very easy to
clean. You remove the spring clip that holds the
capacitor together. All you have to do is to use a
small screwdriver or small needle-nosed pliers to
compress the clip and slide it off of the post that
comes from the top section of the trimmer. You do not
have to unsolder the wiring which makes reassembly
very easy.
Remove the top and the rubber gasket. Usually the
gasket is "stuck" to the top. Carefully peel the
gasket from the top. Carefully remove the flat plate
from the top. You will probably have to use an
"X-acto" knife slipped between the top and the plate
(or a single-edged razor blade works quite well).
Normally just "touching" the seam between the plate
and the top will cause the plate to be released. Do
this very carefully so that you don't break the
ceramic. "Freezing" of the plate to the top is the
most common problem of these capacitors. What happens
is that when the two parts are "frozen" together the
plate turns as well as the top and you cannot ajust
the trimmer. If the assembly turns very far in this
"frozen" condition then you loose contact with the
lower portion of the capacitor and no connection is
made (the capacitor is effectively eliminated from the
circuit).
Use alcohol to clean the flat plate as well as
cleaning the top and the gasket (you might also use
one of the contact cleaners but make sure that no
residue is left behind). Allow to dry completely
(about a minute, or so, when using alcohol). Replace
the gasket on the portion that is still attached to
the unit making sure that the opening in the gasket
allows the spring contacts to come through.
Next put the flat plate on the top with the plating on
the plate showing outwards. Then reinstall top making
sure that the center of the plating on the plate makes
contact with the spring contacts. Finally, hold the
top of the capacitor in place and turn the unit on its
side. Slide the spring clip back onto the stud from
the top making sure that the little positioning
"dimple" mates again to the phenolic base of the
capacitor and that the clip "locks" into place.
Of course you will have to do a complete realignment
of the unt, but 99.9% of the time you will have
restored the capacitor and it will function completely
normally.
Clean all of the capacitors before turning the unit
back on. What I do is to record the value of the
capacitor at each position (there are 2 or 3 values of
capacitors used, not just the 8-50) and take all of
them apart to clean. Then reassemble putting the
correct value capacitor in the proper position. You
will have to segregate the plates in terms of values
as well since they are different between the various
absolute values before cleaning.
It takes longer to read these instructions than it
takes to disassemble, clean, and reassemble the
capacitor.
I have done this to many hundreds of these ceramic
capacitors in all sorts of rigs including the S-Line,
KWM-2 series, etc. So far, I have been "lucky" and
haven't broken a single flat plate (but, my time is
coming!).
Glen, K9STH
--- "Dr. Gerald N. Johnson, electrical engineer"
<[email protected]> wrote:
you need to attack the Erie 8-50 trimmers for each
band switch position. They have a tendency for their
internal connection from shaft to terminal (accessible
on the bottom side) to go open.
It is also possible that the ceramic may be stuck
making rotation difficult of impossible. Then
replacement may be necessary.
=====
Glen, K9STH
Web sites
http://home.comcast.net/~k9sth
http://home.comcast.net/~zcomco
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--__--__--
Message: 5
From: "W0YG Charlie Summers" <[email protected]>
To: "Collins QTH.net Reflector" <[email protected]>
Date: Sat, 12 Jul 2003 02:23:25 -0000
Subject: [Collins] More 310B-1 coils
I have found more of the 310B-1 coils with five pin ceramic base. I have a
10M JEL, a 15M JEL, a 20M JCL and a blank base. All coils are in excellent
condition with no broken insulators. I want $35.00 plus $4.00 shipping for
all.
Thanks and 73,
Charlie, W0YG..>>
--__--__--
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End of Collins Digest