If you have bolts thru the lams have you torqued them to the point of
twisting them off? If you haven't you might want to loosen then and add
some more varnish to the lams while they're loose and then torque them.
Another possibility: Many of the transformers in microwave ovens have a
bead of weld across all the laminations and I've seen this on rectifiers
used in Telco applications. Keeps them quiet and I and has some
negatives like letting line spikes thru but on a filament that is
meaningless. Lam eddy currents area dead issue as I've heard that the
old Bell Labs had accepted this practice.
I had a 30S-1 with minor buzz but when I added 100 volts to the screen
the hum was about to drive me nuts but torquing to lams solved the
problem, I twisted off a couple of bolts.

--
73
Hank WD5JFR
"raypsi" wrote in message
...
Hey all:

I tore down a transformer I got from ebay it was a Zenith TV power
transformer from days gone by. Re wound it with 17AWG wire on the
secondary and primary. It powers up my 4-1000A filament nicely with
7.25VAC from 120VAC mains. I used a penta-filar winding on the
secondary. Shimmed the bobbin in the core window with some 1/8 thick
virgin teflon. Epoxied the windings to the bobbin. This was a 240VA
transformer and now is a 83watt buzzer / 157watt filament transformer.

So what is the cheapest I can gits away with sealing these laminations
from buzzing, I used up all my epoxy sealing the windings.

73

n8zu