[Hallicrafters] HT-37 low voltage rectifier

[Riley Hollingsworth]

I have re-capped the HT-37, gone over it and fired it up.  I haven't loaded
it yet. 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.  I'll just leave the tube in to do the performance test,
but why would it cause the transformer to buzz ? The transformer is
perfectly quiet without the solid state LV.  I think at least one e mail
said to not replace the LV rectifier with a solid state---looks as if I'm
about to find out why!