[Hallicrafters] HT-37 low voltage rectifier

[Fred Olsen]

Riley Hollingsworth wrote:
> I noticed a medium level buzz in the power transformer that
> disappears when I take the low voltage solid state replacement
> out and put the 5V4 back in.

Riley, I don't have an HT-37, and am not even a Ham, but noticed that 
several people went off on the usual track of raised B+ or even missed 
that you had the buzz WITH the SS rectifiers.  Since you apparently can 
swap at will between the tubes and SS, I infer that you have left the 
filament leads connected to the sockets.  What occurs to me is that you 
might be hearing corona inside the transformer from the now-unloaded 
filament windings.

As I understand it part of the weakness of these transformers is due to 
heat deterioration, which removing the filament load will help, but also 
there seems to be a history of failure due to the voltage gradient on 
the filament windings.  I'd suggest trying complete disconnection of the 
windings from the sockets.  If it still buzzes you might try swamping 
the open windings with a minimal resistive load, say 5 or 10% of normal 
current.

Anyone with further thoughts on this please chime in.

Good luck,
Fred
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