[BillB]

Well, after a few glorious days the 24v aikido died on me. 

The power supply is cycling between 0-8v but when removed from the circuit is steady at 24.1v

I removed all the power leads and reconnected only the heater leads, the psu put out 24v and the heaters lit up rather quick...I had been waiting nearly a minute before they were visibly lit but not having any prior 6gm8 or series heater circuit experience I figured this was normal...and I do have some rather mondo caps on the heaters too.

So hoping that it was just a poor connection I reconnected the B+ and the PSU started cycling again...something is amiss but what? Nothing looks physically burnt or anything catastrophic like that...could a valve still be bad? I checked the getter flash on all and there is no white so none of them appear to have lost vacuum.

Maybe a regulator? There are 4 LM317s on the headphone side of the circuit...these are the only things I can think of that could have failed without noticing.

Any advice as to how to go about finding my dastardly music robbing culprit would be greatly appreciated!

All this on a day when I got a Monarchy SM-70 Pro too  . At least my VTL is still operational and singing sweetly right now.

[BradJudy]

Assuming you already did a visual inspection for shorts (I've had mounting screws short things and found the problem with my SI was a whisp of solder that would short when things were wiggled right), I'd try an ammeter inline and double-check how much current is drawn with just the heaters and then with everything. 

[BillB]

Good thinking...I didn't even check current draw.

[lord_glum]

FYI,
Better check how much current you expect to see or you may pop a fuse or your meter if its higher than 2A.  Most commercial meters don't go over 2amps.

Jvo

[ghpicard]

You can also try removing the 6GM8s and then plugging them one by one see if any of them is shorted. Not usual but it can happen. Also this will help you discard shorts produced by little metallic debris between tube pins.