[R-390] R-390A Power Supply

[Bob Camp]

Hi

I'd clean up the rust, patch it up with some body putty, re-spray it and move on. There is probably a half inch of tar between the casing  and any part of the transformer. Of course you *may* have the magic one with an air bubble in the wrong place. Normally the air gap is on the terminal side of the casing. 

If it ohms out ok, I'd apply power and see what happens with it running into no load. If it pulls significant current no load, that's not a good sign. Smoke, fire, explosions, blown main breakers, and zombie attack are also not a good sign. 

Bob


On Mar 15, 2013, at 4:26 PM, rbethman <rbethman at comcast.net> wrote:

> Bob,
> 
> It really is only a bit of rust on the top. So it may well be good.
> 
> I've got another one on its way from another list member.
> 
> The terminals are allk clean and look good under the chassis/terminal strip area.
> 
> I may just check it for bad readings with a VTVM. Who knows? It may really be in good shape!
> 
> Bob - N0DGN
> 
> On 3/15/2013 4:19 PM, Bob Camp wrote:
>> Hi
>> 
>> I assume we're talking about the power transformer on the power supply module in the R-390A here…
>> 
>> There's not a lot of use opening up the transformer. Once you get the thing open, you find that it's potted with a wonderful black tar. I suppose you could dig the tar out, but then you have the transformer siting there loose with no way to mount it.
>> 
>> If the transformer is shot, it's relatively unlikely to be an easy fix. Most common failure is either an open winding or a short. They tend to happen where the heat is high, so deep in the transformer.  Repair involves knocking the laminates apart, pulling the windings, unwinding to the point of failure, rewinding and re-wrapping. Then you are off to re-doing the laminates, re-potting, and re-sealing the enclosure. Been there, done all that, no fun at all.
>> 
>> If it's still ok (but ugly) I'd leave it. Eventually power transformers will become a scarce item.
>> 
>> Bob
>> 
>> On Mar 15, 2013, at 3:37 PM, rbethman <rbethman at comcast.net> wrote:
>> 
>>> I've been looking at a power supply that I have here, and really do not intend to use.  (It is a corroded Blue Striper Module.)
>>> 
>>> Looking at the method used to "seal" these, you can most likely anticipate destruction attempting to open it.
>>> 
>>> It is WELL sealed by soldering the lid on it.  There is a spot on the side where you can see that solder was applied to flow by capillary action around the entire top.
>>> 
>>> I was curious to consider opening it up.  However, after seeing this sealing method, destructive dis-assembly really doesn't make me enthusiastic about this.
>>> 
>>> Bob - N0DGN
>>> 
> 
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