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(We solved this mystery, but not before it got the better of us for a half day)
We got an ol' Premier 50 combo amp in the shop. I went over after one of the guys pulled the back panel off to take a look at what we were dealing with. The first thing I noted was that the tubes had numerical designations I wasn't familiar with.
So, I go back to my bench and continued working and a few minutes later I hear "you know anything about a 774 tube?? See what you can find out. Nothing comes up on Duncan's TDSL?"
Tracking down any manufacturing data published by Multivox/Premier is considered archeology at this point. But I've never, and I mean ever stumped Duncan and Frank's tube data archives before. Seems no one has heard of a 774 tube before.
It didn't take long for us to know we both were getting nowhere. So, we set it aside and sent out word to a collector/dealer we know of in Western Mass, to see if he came up with anything. Sometime later on, out of the blue, I hear my boss chuckle and says. "Ha! we've been looking for a tube that doesn't exist... I bet it's a friggin 'Z' with the bottom of the letter gone, not a 7!" I think, oh right – 7V heater... 4 electrodes?? Yeah, 7Z4 sound much more like a rectifier tube now. Wouldn't ya' know, there are datasheets for days regarding a 7Z4.
Okay, so it may not have taken a half day to crack the case, but it was sure long enough to feel like an arse. In my 3 weeks of doing this so far, something new always seems to pop up and trick me into chasing gremlins that aren't there.
So, this is similar to what we saw.
I keep having to remind myself not to be convinced of anything until it has been tested, confirmed, and repaired. Of course, the problem with this philosophy is it's untested, unconfirmed, and subject to change.
We got an ol' Premier 50 combo amp in the shop. I went over after one of the guys pulled the back panel off to take a look at what we were dealing with. The first thing I noted was that the tubes had numerical designations I wasn't familiar with.
So, I go back to my bench and continued working and a few minutes later I hear "you know anything about a 774 tube?? See what you can find out. Nothing comes up on Duncan's TDSL?"
Tracking down any manufacturing data published by Multivox/Premier is considered archeology at this point. But I've never, and I mean ever stumped Duncan and Frank's tube data archives before. Seems no one has heard of a 774 tube before.
It didn't take long for us to know we both were getting nowhere. So, we set it aside and sent out word to a collector/dealer we know of in Western Mass, to see if he came up with anything. Sometime later on, out of the blue, I hear my boss chuckle and says. "Ha! we've been looking for a tube that doesn't exist... I bet it's a friggin 'Z' with the bottom of the letter gone, not a 7!" I think, oh right – 7V heater... 4 electrodes?? Yeah, 7Z4 sound much more like a rectifier tube now. Wouldn't ya' know, there are datasheets for days regarding a 7Z4.
Okay, so it may not have taken a half day to crack the case, but it was sure long enough to feel like an arse. In my 3 weeks of doing this so far, something new always seems to pop up and trick me into chasing gremlins that aren't there.
So, this is similar to what we saw.
I keep having to remind myself not to be convinced of anything until it has been tested, confirmed, and repaired. Of course, the problem with this philosophy is it's untested, unconfirmed, and subject to change.
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