soapfoot
Well-known member
Greetings. I was given an Ampex 1" 8-track. It's extremely clean, and I was told it was in working condition except for a bad bias oscillator. Heads look to be in surprisingly good shape.
These machines, of course, have two power supplies-- one with a master bias oscillator (powering channels 1-4) and one without (powering channels 5-8).
There are lots of multipin connectors on both PSU enclosures. Some were disconnected when I acquired the machine. I identified the one with the master bias oscillator, labeled where each multipin cable went, and pulled it. Identified an exploded electrolytic cap, replaced it (and a few others in the enclosure, for good measure), thinking I had probably fixed the machine. I did not think to attempt power-up before pulling the supply and performing the repair.
I attempted power-up, and it tripped the breaker in the studio control room. There are 3 fuses on the front of the machine, under the transport controls-- all three fuses were intact and not blown. There is a 1.5A slo-blo fuse on each PSU enclosure. I checked these 2 fuses and they were... missing?
So my question is, what could cause a fault that would make the breaker in the studio trip, even without a fuse in either power supply? If anyone knows these machines, I'd appreciate any leads. I feel there must be something connected incorrectly with the two PSU (I admit to not having researched how it all connects, I just labeled the connectors and tried to put it back how it was). I do have a 440-B service manual, but not for the 8-track.
I feel like it has to be something simple. Any leads? I know Brian Roth knows these machines-- does he still post here?
Thanks!
These machines, of course, have two power supplies-- one with a master bias oscillator (powering channels 1-4) and one without (powering channels 5-8).
There are lots of multipin connectors on both PSU enclosures. Some were disconnected when I acquired the machine. I identified the one with the master bias oscillator, labeled where each multipin cable went, and pulled it. Identified an exploded electrolytic cap, replaced it (and a few others in the enclosure, for good measure), thinking I had probably fixed the machine. I did not think to attempt power-up before pulling the supply and performing the repair.
I attempted power-up, and it tripped the breaker in the studio control room. There are 3 fuses on the front of the machine, under the transport controls-- all three fuses were intact and not blown. There is a 1.5A slo-blo fuse on each PSU enclosure. I checked these 2 fuses and they were... missing?
So my question is, what could cause a fault that would make the breaker in the studio trip, even without a fuse in either power supply? If anyone knows these machines, I'd appreciate any leads. I feel there must be something connected incorrectly with the two PSU (I admit to not having researched how it all connects, I just labeled the connectors and tried to put it back how it was). I do have a 440-B service manual, but not for the 8-track.
I feel like it has to be something simple. Any leads? I know Brian Roth knows these machines-- does he still post here?
Thanks!