Howard 437A

[JohnJack M Iverson]

Dave, the lesson here is   do  not  "hose the chassis off" if you did get
water in the tx, the best way is to put it (the tx) in the oven at 235
degrees for about 1 to 2 hours. after removing it, drizzle a good grade
of transformer varnish on the exposed windings   you will have to take
the covers off to do this.
a much simpler approach would be --  do not get any wound, insulated
devices wet--   ok?
   I shall now wait for the comments from the group.    don't hit me too
hard..   old jack

On Sun, 11 Jul 1999 11:57:58 -0400 David Franklin
<dfranklyn at MINDSPRING.COM> writes:
>
> I thought that I would share my experience with the above receiver.
>
> When I got the receiver it appeared to be complete.  All of the
> bypass
> capacitors had been changed, judging from the capacitors used, I
> would
> estimate 25 years ago. After initial checks for shorts and bad
> tubes,
> I brought it up on my Variac.  The radio worked but had low
> sensitivity
> on all bands and slight hum in the audio.  The radio was very dirty
> inside and out and had nicotine stains and blue tape gum on the
> front
> of the cabinet.
>
> I washed the cabinet and the chassis with Simple Green and hosed it
> off.
> I used a tooth brush on the hard to clean spots on the cabinet,
> avoiding
> the painted on lettering. I then blew the water off and dried the
> radio
> in the sun for 1 hour.  Then I put the chassis in the oven and
> manually
> controlled the temperature keeping it between 150 and 180 degrees
> for
> 2 hours.
>
> The radio cleaned up beautifully.  All of the stains came off the
> cabinet
> and the copper chassis shined.  Next step was to re-string the dial
> cords
> and replace the line cord with a 3 conductor for safety. I also
> tested the
> filter capacitor with my capacitor checker and it checked good.
>
> When I powered it up 2 weeks later for alignment, the filaments lit
> but at
> first there as no sound in the audio.  After about 5 minutes the
> sound
> came on as was as before.  Then while getting ready to connect the
> generator,
> I noticed a wisp of smoke from under the chassis and pulled the
> plug.  The
> smoke was comming from the power transformer.  I pulled all of the
> tubes
> and checked again for shorts.  I powered it up without the tubes,
> the power
> transformer again became very hot and sizzled.
>
> My guess is that while cleaning the chassis that the cleaner and
> water
> found its way into the transformer and broke down the shellac
> insulation
> causing the transformer to short internally. I did not do anything
> to
> protect it where the leads come out.  Will next time!
>
> Thanks for listening.  I would appreciate any comments or
> experiences
> from the learned group.
>
> Dave Franklin
>
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Jack Iverson    K0EWU    jackiv at juno.com
ARRL,  IEEE LM,  RCA, AMI, ARCI, QCWA,CCA

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