[TMC] GPT-750 HV transformer

[Tony Faiola]

Hello Andrew:
First of all, I was going to take a jpeg of the front of this HV  
transformer and attach it to this email, however I'm not sure if  
attachments are allowed on this site.  It is perplexing to me how  
this transformer arrived in the condition mentioned by you.  By  
reading through the lines of your email, it seems someone twisted the  
HV threaded terminal on the front of the transformer (all the  
terminals are on the front of this transformer), and broke it off.   
He cut the top off to attempt to repair or replace the stud.  The  
porcelain insulators are popular and can be obtained as well as the  
threaded screw.  This may be all that is require to get it  
operating.  Be careful when testing, you are dealing with lethal  
voltages!

We (TMC engineering department) purchased almost all of our  
transformers from Berkshire Transformer Company in CT.  I believe  
they are no longer in business.  This is a very heavy mil spec  
transformer (as you are aware).  Central Armature Works in or near  
D.C. used to repair devices such as motors, etc, but it might be  
costly for them to repair and pot.  There is potting material  
available in the marketplace.  A new transformer is available, open  
frame type, to replace yours and it will fit in the same location in  
the GPT-750 bottom power supply deck. Collector purists would gag  
over that option.  You may want to investigate that option also.

If you require more information, chime in again, and someone might  
offer more suggestions, and please as a final note, have someone  
assist you with moving that transformer!

73, and good luck, Tony, K3WX


On Sep 22, 2010, at 3:31 PM, John D. Kopke wrote:

> Hello all,  I finally have some inspiration to work on my GPT-750  
> (A2) and plan to
> use it as a CW transmitter.At the moment, it's only capable of CW .  
> I'm starting
> from the bottom -up working in the power supply section ,checking  
> wiring and
> cleaning . My high voltage power supply (now sitting in the garage)  
> has had some
> problems in the past apparently due to arching, and has been  
> modified to some
> extent .The top of the the transformers outer steel shell has been  
> cut off
> (neatly ) around the edges and two of the taps.  I recently noticed  
> the #6 tap/stud
> is broken off inside it's threaded socket . How should I go about  
> repairing this ?
> I have not attempted to remove the broken screw as to not damage it  
> any further.
> Also, I'm wondering if there's anyone in the Baltimore/Washington  
> area with
> expertise in repairing potted,(for lack of better term )  
> transformers. Before I
> noticed the broken stud I planned on cutting some sheet steel and  
> recovering the
> cut area with JB weld ,the edges are very sharp where it has been  
> cut open. I see
> four crater-like holes in the top of the XFMR's potting material,  
> apparently where
> standoffs were? I'm wondering what could be used to fill in those  
> area's.But the
> firt concern is the broken standoff/stud.  Many thanks fo any  
> insight on this
> matter.  All the best , Andrew Kopke, KB3JUH
>
>
>
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