I got this huge Ampex in trade last week, and it won't record at all.
The bias amp is in the power supply, and I have to admit, i don't know what's gone wrong with it.
It's early enough; that the bias signal was amplified by a 2n3053 (silicon) and the pnp, a Germanium, so I'm thinking it's late 60s at least.
All the other relays and lights seem to be doing their jobs... the rec/play modules needed recapped, so i did one completely and took the other one out, just in case it was shunting the bias signal somehow, but the problem persists.
I've used my scope, but the manual really doesn’t go into much detail of where to check for the signal, when not checking at the modules, and I've tested every leg of every transistor, and i have a newer scope. I have two multi-testers that have frequency counters, but nada.
The germanium transistor in the a/b amp for the bias was dead, but i figured there should be some complimentary pair out there in silicon transistors to replace these old things with, right? I've used some modern transistors that seemed like they should work, but I'm starting to think this thing is too decrepid! I found another transistor out last night, the two smaller ones that are just before the adjustable coil.
The adjustable coil doesn't want to turn, as well. I'd like to test it outside the circuit, but would have to fool it into thinking it was in record mode, and that's rather complex as well. It's getting the right voltage, but i am having a hard time getting a signal of any type from the board.
I really wish the manual detailed more about testing, or rebuilding the power supply/bias amp, or that there was more out there on these famous work horses. If the adjustable coil is toast, what will work in it's place? But given there's no 150k anywhere, I don't know what to do next. Do they make a modern standalone bias amp i could inject into this?
Sorry for the barrage of questions, but really am trying to get one good mastering deck on line.
Pics of the unit and the two transistors i used to try and get it running. It seems they should do something? Pinouts carefully matched.
The bias amp is in the power supply, and I have to admit, i don't know what's gone wrong with it.
It's early enough; that the bias signal was amplified by a 2n3053 (silicon) and the pnp, a Germanium, so I'm thinking it's late 60s at least.
All the other relays and lights seem to be doing their jobs... the rec/play modules needed recapped, so i did one completely and took the other one out, just in case it was shunting the bias signal somehow, but the problem persists.
I've used my scope, but the manual really doesn’t go into much detail of where to check for the signal, when not checking at the modules, and I've tested every leg of every transistor, and i have a newer scope. I have two multi-testers that have frequency counters, but nada.
The germanium transistor in the a/b amp for the bias was dead, but i figured there should be some complimentary pair out there in silicon transistors to replace these old things with, right? I've used some modern transistors that seemed like they should work, but I'm starting to think this thing is too decrepid! I found another transistor out last night, the two smaller ones that are just before the adjustable coil.
The adjustable coil doesn't want to turn, as well. I'd like to test it outside the circuit, but would have to fool it into thinking it was in record mode, and that's rather complex as well. It's getting the right voltage, but i am having a hard time getting a signal of any type from the board.
I really wish the manual detailed more about testing, or rebuilding the power supply/bias amp, or that there was more out there on these famous work horses. If the adjustable coil is toast, what will work in it's place? But given there's no 150k anywhere, I don't know what to do next. Do they make a modern standalone bias amp i could inject into this?
Sorry for the barrage of questions, but really am trying to get one good mastering deck on line.
Pics of the unit and the two transistors i used to try and get it running. It seems they should do something? Pinouts carefully matched.
