I've been watching this with increasing interest; I've done valve jobs
with less hoo,haa

As always i am going to suggest the obvious, the first question is if any one in your house has a multi meter
as in a volt/ohm meter? Second do you have a wiring diagram, for this
beast ? Can someone in your house read volt meter and follow a wiring diagram
if you can answer yes to at least two of the above questions ;I believe you can get out of this vortex of evil.
Remembering that this is D.C. voltage and is ground sensitive, )or you get minus readings )
Make sure you have power EVERY WHERE YOU ARE SUPPOSED TO, AND AS THE MESIAH SAID ''CHECK YOUR GROUNDS
When you can follow the power in and power out you are nearly home free.
Make sure the socket the bulb is sitting in has power and ground,make sure the bulb isn't burned out or broken
Remember the obvious is not always the culprit, but when you have
eliminated everything else what remains no matter how absurd is the answer ( r. Heinlein)

I just replaced a $2000 board in a machine at work that apparently failed because it felt like it.

ALWAYS DO THE EASY STUFF FIRST.ALWAYS ALWAYS you're going to do it eventually and little stuff can grow up to make you nuts.

If you live in So.Cal I know of two (one in particular )
called THE HOT WIRE, and for electrical nightmares they are my first choice, they are honest and very, good

if symptoms persist, take two beers and call me in the
morning paul in santa ana