[R-390] Power Transformers

[Steve Hobensack]

The power transformers can go bad in a certain way. I have a '62 
Imperial-Tel. Before pitching the trans in the *hit can, I used a 
screwdriver and chizzled off the back plate and removed the potting near the 
plate voltage leads. The potting had carbon tracked across the little 
porcelan feed-through bushings. There was a dead short. The repair was easy. 
Break out the tubes and replace with good insulated hook-up wire, then melt 
the potting back in. Be sure to do both hv bushings.
73..Steve..kj8l


>From: Llgpt at aol.com
>To: ham at cq.nu, r-390 at mailman.qth.net
>Subject: Re: [R-390] Power Transformers
>Date: Sun, 25 Jul 2004 23:04:36 EDT
>
>I have had 33 pass through my hands, none were bad. Picked up 7 R-390A's
>today, haven't checked any of them out yet, but expect all of them to be 
>fine.
>Also, 1 R-390 and expect that to be ok too.
>
>Les
>
>
>In a message dated 7/25/2004 9:45:29 PM Central Daylight Time, ham at cq.nu
>writes:
>Hi
>
>One of the things that there "are no more of" is the power transformer
>in our favorite radio. Given the way they made these we are unlikely to
>get together and make up a batch of them. Obviously this is not the
>only part in the radio that might be in this category ten or twenty
>years from now. Let's just focus on the power transformer right now.
>
>I have never seen a R-390 with a blown power transformer. How common is
>power transformer failure in these radios? Certainly it is not in the
>top ten or even the top 20 observed failures. That alone is an
>encouraging thing. It is especially encouraging when I compare it to
>the number of computer power supplies I seem to see.
>
>There are things we can do to lengthen the life of the transformers we
>have *if* it's an issue. All of these things have an impact so you
>really don't want to fix one thing only to break another.
>
>So, has anybody ever seen a blown power transformer in one of these
>radios? If so do you have any idea what caused it to fail?
>
>     Thanks!
>
>         Bob Camp
>         KB8TQ
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