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Look what i found.

what are the small tubes? There is an official Dyna schematic for the A430 in an "modernized Williamson" circuit with 6SN7, but it wouldn't be hard to recreate that with 9 pin twin triodes.

1697337171267.png
 
That's a really intriguing system. I'm sure you'll get around to it sooner rather than later. ;-) The preamps look very fine, and I'm curious to know if the amps are a Williamson variation, or maybe a UTC-style "ultralinear" circuit, or what. Either way, I bet if you get them restored and running, they'll sound terrific!
 
And how about that vintage doorbell transformer being used for bias. That's resourceful!

Whoever built these amps may have actually designed them too, after pouring through manuals, magazines, books, etc. Might be a good idea to see where they're at stability wise, etc.
 
I put in a quote at hayseed for the cans to rebuild both amps. There's really not a lot to em in terms of components. The can caps in this one are wired to octal plugs. So I asked hayseed about getting those custom made.
I think I counted 3 bathtubs for coupling caps and one electrolytic on the bias supply, 2 cans above chassis and a handful of resistors. When their time comes, I should have them going in no time flat, and yes I'm very excited to put them through the wringer on the test bench.
 
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New cans should be about $150 maybe $200.
I might have another $200 into various caps, Jack's, and whatnots in order to button them up for Long term service. I'd like to put bottom panels on them and also give them walnut skirts.
They may also get a set of 6550 Power tubes if I think the transformers will handle em. The tubes in it are marked 6ca7, but they look a whole lot like EL34 to me.
 
trainbuftony said:
New cans should be about $150 maybe $200.
I might have another $200 into various caps, Jack's, and whatnots in order to button them up for Long term service. I'd like to put bottom panels on them and also give them walnut skirts.
They may also get a set of 6550 Power tubes if I think the transformers will handle em. The tubes in it are marked 6ca7, but they look a whole lot like EL34 to me.
Click to expand...
EL34 "continental slimmies" pentodes. Actual 6CA7 beam tetrodes look like a junior 6550.
 
trainbuftony said:
New cans should be about $150 maybe $200.
I might have another $200 into various caps, Jack's, and whatnots in order to button them up for Long term service. I'd like to put bottom panels on them and also give them walnut skirts.
They may also get a set of 6550 Power tubes if I think the transformers will handle em. The tubes in it are marked 6ca7, but they look a whole lot like EL34 to me.
Click to expand...
6CA7 was originally just the RMA designation for the EL34, it was put on Dutch Philips made EL34s long before there was a beam power version made domestically.
 
Pio1980 said:
Interesting.
I've always differentiated them by configuration.
Click to expand...

In the 50s the EL34 was sold in the USA as the Mullard EL34 (from England), and the Amperex 6CA7 (from Holland). The USA beam power interpretations of this tube seem to have come later in the 1960s. But all the Japanese versions which are nearly identical to the Mullard EL34 also get called 6CA7. Some companies like Ei and Sovtek made or make both pentode and beam power versions, calling the Pentode version EL34 and beam power 6CA7, and I think this is where the hard distinction came from. Then there's the GEC KT77, which is another beam power tube intended to replace the EL34.

In any case, if it were my amp I'd leave those original tubes in place, since I don't think I've met many bad sounding EL34 amps!
 
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maxhifi said:
In the 50s the EL34 was sold in the USA as the Mullard EL34 (from England), and the Amperex 6CA7 (from Holland). The USA beam power interpretations of this tube seem to have come later in the 1960s. But all the Japanese versions which are nearly identical to the Mullard EL34 also get called 6CA7. Some companies like Ei and Sovtek made or make both pentode and beam power versions, calling the Pentode version EL34 and beam power 6CA7, and I think this is where the hard distinction came from. Then there's the GEC KT77, which is another beam power tube intended to replace the EL34.

In any case, if it were my amp I'd leave those original tubes in place, since I don't think I've met many bad sounding EL34 amps!
Click to expand...
I've preferred the beam tet's in mine, but haven't tried all iterations of the pentodes.
 
I have an RCA 6CA7 that I got in a box of stuff, its a Blackburn Mullard EL34. Handy since I needed one of those to fill out a set.

I like the beam tubes in my Pilot because they give a little extra top end, and the Pilot needs the help. I like the EL34 tubes in my Rauland-Borg amps because they tend toward being bright, and a less-bright tube is a good match.
 
There's one more critical detail I left out of the discussion of this set, because it's pure speculation. As many of you know I dabble in automotive witchcraft as well. The owner of these amplifiers gave them to Jerry because Jerry rebuilt 4 or 5 radios into one functional radio for the gentleman's 1933 pierce arrow. (A gentlemens car if there ever was one)

Hit rewind.

At my last job, my previous boss asked me if I wanted some speakers which he
Wasn't using. He loaded them with the front loader of his John deere back hoe, due to their tremendous weight. I got them home and found Altec 808 horns and 18" field coil western electric drivers in them. Their owner, according to John, also was the owner of a 1930s pierce arrow.

I think there's a strong possibility that these speakers and these amplifiers at one point previously belonged to the same gentlemen.

What do you think?
 
trainbuftony said:
There's one more critical detail I left out of the discussion of this set, because it's pure speculation. As many of you know I dabble in automotive witchcraft as well. The owner of these amplifiers gave them to Jerry because Jerry rebuilt 4 or 5 radios into one functional radio for the gentleman's 1933 pierce arrow. (A gentlemens car if there ever was one)

Hit rewind.

At my last job, my previous boss asked me if I wanted some speakers which he
Wasn't using. He loaded them with the front loader of his John deere back hoe, due to their tremendous weight. I got them home and found Altec 808 horns and 18" field coil western electric drivers in them. Their owner, according to John, also was the owner of a 1930s pierce arrow.

I think there's a strong possibility that these speakers and these amplifiers at one point previously belonged to the same gentlemen.

What do you think?
Click to expand...
I once fixed a radio for a Deusenberg J for someone.

Pierce Arrow had and has a magical allure as vintage cars to me.
Wondering if those PAs were straight-8 or V-12. I encountered one of each in my youth that weren't within reach of my means. The PA V-12 engines lived on in Seagraves fire engines after PA closed up in the mid-latter 1930s.
 
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