"EADGBE" wrote in message
ups.com...

The GOOD news: This 3.5v tap is NOT dead. It DOES produce voltage.

The PUZZLING news: Instead of the 3.5v AC specified in the service
manual, I am measuring a steady 7.97v AC.

Are you measuring with the display not connected? The transformer's output
without a load will be higher than with a load.

HERE IS THE FAULT I DISCOVERED: As I mentioned before, the two wires
of the 3.5v supply (which is actually measuring at 7.97v) are each
connected to their own 1-ohm 1/4-watt "R-FUSE" before proceeding to
the jumper wire that goes to the flourescent display.

I don't really know what an "R-FUSE" is, actually. They just seem to
be regular dull blue 1-ohm metal film resistors. But the schematic
symbol shows a small rectangle with symbols for a fuse and a resistor
inside the rectangle, connected in series.

Is it possible that these are indeed metal film resistors BEING USED
AS FUSES as well as being a voltage drop for the "3.5v" supply which
is actually 7.97v?

Quite possible. These are called "fusible resistors", and they're designed
to protect the circuit by blowing up if too much current flows through them.
If you combine loading on the transformer and two 1-ohm resistors in series
with the filament, that might give you the 3.5V you want.

Next step: put the ohmmeter across each of the 1-ohm resistors and see if
they're blown.

Peace,
Paul