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TRANSFORMER DISASSEMBLY

 * Original msg to: Esondrmn-at-aol-dot-com

 > From: Esondrmn-at-aol-dot-com
 > To: richard.quick-at-slug.st-louis.mo.us
 > Subject: Transformer disassembly

 ES> Richard,

 ES> I disassembled my first transformer today, using your freezing 
 ES> method. What a mess, frozen chipped tar all over the place. 

It sure beats the other ways I have tried it, trust me. At least
the chips can be swept up without having to deal with hot, or 
solvent rich goo. The goo is a REAL MESS.

 ES> It is now soaking in kerosene. Once I get it cleaned up and dry 
 ES> again should I test fire it just as it sits?  

Make sure it is dry enough that it won't catch fire first, then test
away.

 ES> Should I take the paper wrappings off of the secondary to try 
 ES> and find the short?

No, these multi-layer secondary coils are machine wound, and unwrapping 
them is just like opening the proverbial "Pandora's Box". If unpotting 
them from the tar is not sufficient to bring them back to life, then the
open or shorted coil should be pitched in the trash. You can unwind them
for the education, just don't expect to be able to put them back together.

If one winding is bad, you can still salvage 1/2 of a power supply, or
shop around for a second identical transformer that is bad and put two 
good windings together one core.

 ES> This transformer is a 12kv, 120ma Gardner - very heavy.  The primary
 ES> windings look like 14 guage wire.  I did not see any shunt plates.  
 ES> Do I have to take the windings off the core to see those?

The shunts are located between the primary and secondary coils. There
is one shunt on either side of the primary. The shunts are frequently
a removable block of stacked plates, but they may be an integral part
of the stamped core plates. These shunts act as a magnetic bypass to
prevent the full magnetic field flux from developing in the secondaries. 
The best way to directly access the shunts is to open the core and 
remove all of the windings.

 ES> I did get four or five coats of polyurethane on my 6.0 x 29.5 inch 
 ES> PVC coil form.  I will wind it this weekend  and add four or five 
 ES> more coats over the wire. Thanks,  Ed

Sounds like progress to me. Let me ask a couple of questions.

1) Did you find any power factor correction capacitors in the tar block?
2) Did this transformer work before you unpotted it?
3) Why didn't you start with a dime a dozen 30 mA neon to unpott the
   first time around? My first unpotting attempt resulted with a screw-
   driver driven right into the heart of the one good secondary winding.

Just curious

Richard Quick




... If all else fails... Throw another megavolt across it!
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