TENER
Well-Known Member
I used a dental mirror to look at the marks on the other transformer and I still see no numbers. Just (TP 102 A).
3 Grommes Precision G 101 A, 100 watt mono block tube amps
- Thread starter TENER
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soundmotor
super modified
Fair point. It is a Novar base though, same as the 7868 that was in common use in the early 60s. Radiomuseum says 1959 for that tube, but I don't know how accurate that is, or if anyone would have been making an amp with it that soon after introduction. 1970 would have been late for a tube amp but not impossible either.
maxhifi
Addicted Member
My bad, they really do look like compactrons one would find in a TV from the mid to late sixties.
I think that radiomuseum meant the novar base dates to 1959, not the tube itself. The RCA data on the 6GT5 it is dated 1963, I still think they're form 1970, but you could be right.
As for 1970 being late for a tube amp, I agree it's late, but it was still definitely the tube era if the end of it.
maxhifi
Addicted Member
Agreed. Bet these amps are going to sound good with the OP's Magneplanars, I'm going to watch this thread. Bass should be good based on the large output transformers, and the fact they use tubes which are affordable as old stock is icing on the cake.
I think the first step is to test those transformers, make sure whatever made the chassis rusty didn't ruin them.
TENER
Well-Known Member
It might be awhile before I get these done. To do them like I want I need to swap a lot of parts from one to the other. I really don't need to but the best looking one has some real problems. You can visibly see the damage. It got hot! Hot enough to melt solder. Her is a pic of one of the resisters pointing straight down after the solder melted away and gravity took over. also look at the one next to it. It got so hot you can't read the values any more. Good thing I have a spare!
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If it torched the cathode resistors, the output tubes are probably done too. Possibly has a leaky coupling cap or the bias supply went kaput. Either will be easy to diagnose and repair, just expect to have to test or replace tubes in these. The tagboard will actually make repairs on this pretty simple.
maxhifi
Addicted Member
1 .Those amplifiers were likely installed in a rack in the utility closet of a large building, connected to those round 8" speakers in the ceiling and everywhere else for PA duty and operated constantly for many years. Most likely the coupling capacitors got leaky, the tubes conducted too much, then they cooked until the tubes either became totally weak, or something else burned out. Hopefully not the transformers, so check those first.
2. The carbonized parts of the terminal strip have to be addressed, once burned, it can become conductive, so that definitely needs to be dealt with before operation.
3. Gotta love the quality.. that's some good old USA workmanship and parts. Clean the chassis, paint the transformers with some barbecue paint, it'll clean up really nice.
maxhifi
Addicted Member
TENER
Well-Known Member
Yes the first thing I am going to test on that one is the transformers. I hope they are still good.
TENER
Well-Known Member
Yes I am probably going to need tubes. I am happy that they are not to expensive.
maxhifi
Addicted Member
http://www.angelfire.com/vt/audio/f106c.html
Schematic here is dated 1971, for the amp's cousin. Looks like a nice circuit, the input stage is kind of creative.
I forgot to mention, your magnepan tympani speakers are what I always told myself I'd get when I grow up... How do they sound? Did you refurbish them?
Schematic here is dated 1971, for the amp's cousin. Looks like a nice circuit, the input stage is kind of creative.
I forgot to mention, your magnepan tympani speakers are what I always told myself I'd get when I grow up... How do they sound? Did you refurbish them?
TENER
Well-Known Member
Yes I refurbed them. They sound great but I need a better amp for them. Looks like I might have some now. I got them off craigslist a few years ago for $125.
maxhifi
Addicted Member
That's a lot of work! Those speakers and the quad ESL were what I always wanted most of all. And you stole them for that price! Magneplanars have a flat impedance, ideal for tube amps.
Don't worry about having too much power, it's great to have a lot of power, just don't abuse it.
TENER
Well-Known Member
Here are some better pics of them. Much better than in the back of my dirty van lol. 2 of these have had capacitors replaced and I could probably plug them in but I don't want to take the chance. I am going to take my time with these and do them right. Also they have consecutive serial numbers, Thought that was cool.
