Hi,

It isn't too unusual for a power transformer to be run uncomfortably
hot. The temperature rise is due mostly to i2r losses in the primary
and secondary windings, and partly due to losses in the core. The
transformer manufacturers very often run the transformer with a magnetic
flux that is approaching the saturation point of the core. This results
in the cheapest/lightest transformer possible... But it comes at the
cost of cool operation.

If you remove the 15W filament load due to the 5U4, it will cool the
transformer down a bit, but probably not as much as you would like.

Here is a way to tell: Pull the 5U4, and leave the radio on for
1/2 hour, or so (without HV). Check how hot the transformer becomes.
This t rise is better than the best you can do by replacing the 5U4
with a SS full wave rect. If it is substantially cooler, then you will
get an improvement with the SS rect. Otherwise, you should probably
just live with things the way they are.

-Chuck Harris

k3hvg wrote:
I've got a particularly nice NC-183 in the collection. Although nothing
untoward has happened after a number of continuous hours of operation, I
do notice that the power xformer get noticeably hot.. as in it can't be
touched but for a few seconds. Voltage drop considerations aside (they
can be addressed, after the fact), would using a solid-state rectifier,
in place of the 5U4, provide a noteworthy temp decrease? 15 watts is 15
watts, of course, but I'm curious if anyone's actually made note?
Thanks de K3HVG