Yeah, I lost the original schematic, and the resolution on the online one is subpar, to say the least. Sorry for any eyestrain you incurred on my behalf.

The "floating" chunk of circuitry in the upper-right is a CD4049 and some electrolytic capacitors, acting as a voltage-tripler. It triples the +/- 15V coming out of the wall-wart and feeds it to the phantom power circuit and the 12AX7 plate. I replaced that IC, thinking it burned out, but no results.

My housemate, who's in Ireland, knows where the multimeter is; I'll wait for him to get back before I go further. If I'm getting +48V out of that part of the circuit, I'll just keep going forward until I figure out what's what.

I suspect a short or faulty electrolytics in the voltage-tripler circuit.

The two other ICs on the schematic are the op-amps that form the solid-state half of the mic pre-amp circuit; that part works just dandy. There's a potentiometer that blends the tube signal with the SS signal; there's no tube signal, because because there's no 48V on the plate. No 48V phantom power, either, and the LED that lights up with that part of the circuit doesn't function, either.

I'll report back after I make measurements in the next day or so. I'm doing this so the next person after me might learn from my numbskullery.

I've got the same preamp. I should have the schematic laying around
here somewhere. Let me know if you need to borrow it or take a look
at mine.

Mark

Mark,
If you could scan that puppy and e-mail it to me, that would be a HUGE help.
Is that possible?

Have nothing to scan with. I can mail it to you and just mail it back
when your done. I have no use for it right now. Email your address
if you like.