[Premium-Rx] Racal RA-17L Overheating Problem

[richardreich at aol.com]

Hello,

It sounds like it could be the filter capacitors (the filters in the narrow channels underneath the set). These are well known for causing sudden changes in performance. The situation gets worse when hot.

Regards - R


Sent from my BlackBerry® wireless device

-----Original Message-----
From: William Watson <wwatson5 at sbcglobal.net>
Sender: premium-rx-bounces at mailman.qth.net
Date: Wed, 26 Oct 2011 21:02:34 
To: premium-rx at mailman.qth.net<premium-rx at mailman.qth.net>
Reply-To: William Watson <wwatson5 at sbcglobal.net>
Subject: [Premium-Rx] Racal RA-17L Overheating Problem

Realizing that the RA-17L is not a "premium" receiver by today's standards (but still a pretty good radio!), I wanted to poll the group re a current problem with my RA-17L.
 
It has the top and bottom covers and is housed in the original Racal cabinet.  Works great until it cooks for a couple of hours and then performance suddenly drops way down.  I notice that by the time this occurs, the innards are very hot to the touch---including chassis and power transformer.
 
I am still in the process of isolating the problem.  So far, I have replaced the tubes plus an electrolyic capacitor.  
 
I was just wondering if any of you have any experience with those sets overheating?   
 
Of course, I could rig up a muffin fan, a la the Collins HF-2050 treatment and perhaps avaid the problem, but I would like to find out what is doing it.
 
I expect to eventually isolate the problem, likely to a heat-sensitive capacitor.  I did the customary refrigerant spraying on accessible parts on the bottom, but there are quite a few goodies packed away in the RF and other modules on top of the chassis that I have not yet subjected to that treatment.
 
I am currently in the process of taking a few key voltage measurements before and after failure occurs in hopes of finding a correlation.
 
Any thoughts would be welcome.
 
Joe
W5WBR
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