On Sat, 09 Apr 2011 19:22:57 -0400, Jeff Thies
wrote:



But first do as I suggested in another thread,look carefully for
anything burnt and check the polarity of the line. Make sure the neutral
is neutral. You can measure from the ground prong. See the note in the
schematic. I'm not so sure this didn't arc to the transformer shell,
from looking at the pic. You may wish to measure voltage (AC) from the
transformer shell to a guaranteed neutral.

It's AC so there is no polarity. It's single output, non grounded, so
it doesnt matter which direction either the primary or secondary are
connected. Good to have the white on neutral and the bloack on live,
but it will have NO EFFECT on the operation. - or the life of the
transformer.

It is OK for the transformer to run a little warm, it shouldn't be hot.

There are two kinds of failures, one is a long term thermal failure
(which seemed likely when you said years had gone by), the other is a
transient short, or maybe not so transient. If that is the case then
something else will be bad. It may look burnt, or if it is a diode or
transistor it may just be shorted. You can Google how to test those.

Don't be afraid to put a quick finger on a transistor to see if it is
hot, or on the transformer.

As far as calculating what size fuse, you should know Ohms law. Current
* voltage is watts, or in this case V(olt)A(mps). 120V * 1/4A = 30 VA,
on the out side, 24V * 1.5 = 36 VA.

Note that there is a small surge when you turn on a device. So it may
peak higher at the instant of turning on. A fuse usually can absorb
that. The white ceramics are faster blowing and the slow blow ones
usually have a little coil inside the fuse to show it down and are
marked slow blow. When/if you fix this, leave in the fuses and we can
give you some guidance on more properly sizing them. But some fuse in
the ballpark is definitely better than nothing.

Jeff