DIY PSU for Altec 150A (M11) Coke Bottle.

[RuudNL]

Maybe I missed it in earlier posts, but keep in mind that the Altec 150A expects an 'elevated filament voltage', in other words: the filament voltage should be ~150 V. above ground.

 

[thecr4ne]

Maybe I missed it in earlier posts, but keep in mind that the Altec 150A expects an 'elevated filament voltage', in other words: the filament voltage should be ~150 V. above ground.

Yes, this was addressed by severing the ground trace to isolate the filament voltage from the B+, and insulating the screw ground connection, then tapping off the center of the series zeners for the +150V reference.

I haven't had a chance to get back to this project. I got things to a place where I think it should all work, but when I tested with the mics, I got no sound.
It's possible there's an issue with the internal connections in the mics themselves, or possibly the cables I made (I used Sommer Octave tube mic cable). I did also purchase an actual P518A psu, but I got similar results on initial testing. I haven't yet followed up with that either. It obviously should be recapped and tested more thoroughly. It will also be a basis for comparison once it's properly back to spec.

I still believe in this PSU hack project and look forward to getting it to the finish line, but life has been getting in the way as it tends to do for me.