John Williamson wrote:

EADGBE wrote:

BUT THE NAGGING QUESTION REMAINS: WHY AM I NOT GETTING *ANY* VOLTAGE
READINGS ON EITHER OF THE TWO BLUE WIRES WHEN THE DECK IS SWITCHED
ON???

Have you checked for voltage *across* the blue wires?
If it's an isolated heater supply, either wire on its own will show zero
with respect to chassis ground, but will show 3.5 volts with respect to
the other blue wire.

And when the equipment is working correctly, both blue wires will show a
negative DC voltage too (from the VFD supply).

The filament btw acts as a directly heated cathode in a VFD. The segments that
illuminate are the anodes and the remaining connections are control grids.

It's a big multipin triode.

Graham