[Hallicrafters] HT-37 low voltage rectifier

[W4AWM at aol.com]

Hi Riley,

The buzz is most likely coming from loose laminations in the transformer.  
This is brought about by the increased load of the rectifier filaments which is 
why it s\disappears when you go solid state. You can try to tighten up the 
bolts holding the transformer together.  This sometimes helps, but does not 
always work.  If you have a horizontally mounted transformer, you will have to 
loosen the mounting bolts below the chassis and use an ignition wrench above the 
chassis to tighten the bolts, then retighten the below chassis hardware.

I had a friend whose buzz was driving him up the wall.  In despiration, he 
removed the transformer from the chassis, loosened all the hardware and bumped 
the laminations loose with a rubber mallet.  Then he spray painted the 
transformer, let it dry in the hot sun, tightened it up and reinstalled it.  The buzz 
disappeared.  For all that trouble, I would listen to the buzz, especially if 
it is coming from a "talking" modulation tranny.

73 and good luck with it.

John,  W4AWM


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