Julian,

Any chance the failure is visible, and fixable?

An option here is to get your tranny rewound. There are lots of folks
that offer this service, or you might take it on as a DIY project. If you go
this route, you could simplify the winding task by only making one winding
of 250 vac, and use a full wave bridge rectifier consisting of two silicon
diodes on the negative side (-) and the vacuum tube 5U4 rectifier on the
positive side (+). If you go this route, you can beef up the HV secondary
wire size since there will be room, and it may be easier to handle a larger
wire than what was originially there. You can also modify the turns ratio to
better match today's higher line voltage. I bet the SX-42 tranny was
designed for 110 vac AC mains whereas today we often have about 122 vac at
our outlets.

As a FYI for still working open frame boat anchor transformers, you can
preserve them by vacuum impregnating them with transformer varnish. This
will fill in the voids where a failure is imminent, but hasn't happened yet.
This can be a DIY project where you can use car manifold vacuum, some
tubing, fittings, and a suitable container. Take the end caps off first to
expose the windings. If the wires have bad insulation, you can cut them 1"
from leaving the core, and strip back. Add on new wires and heat shrink the
connection. As for doing the varnish bit, it's neat to watch the bubbles
exit the transformer as the air is pumped from the container, and then when
you let the air back in, that forces the varnish into all the cracks and
pores of the inner area of the transformer. Repeat two more times to get the
job done. Then hang until dripping is over, and bake to cure (temp and time
depends on varnish used). Instead of varnish I have also used electrical
rated RTV thinned out with chlorethane until it is a white milky soup.

Jim
WD5JKO

"jjbunn" wrote in message
oups.com...
I'm looking for a replacement, or a substitute, mains transformer for a
Hallicrafters SX-42 ... the existing one sizzled and died :-(

The specifications a 115V primary, 500V C.T. @ 142mA, 5V @ 3A and
6.3V @ 5.3A, and the mounting holes are 3.75"x3.00".

If anyone knows a likely source for a replacement, please let me know.

Thanks!
Julian