Altec 1567a with Triad transformers...what to do

[thecr4ne]

I just acquired a modded Altec 1567a which, to my surprise, has Triad HS-1s on Channels 1-3 and a Triad HS-50 on the output (Channel 4 still had the original 4722)

This was to be my second 1567a and I was originally planning to restore it to stock, but now I'm considering selling it, or at least the transformers and buying another stock 1567a with the proceeds.

Thoughts?

 

[emrr]

You got an upgrade!

 

[thecr4ne]

Yeah, would be nice to add a 4th HS-1 and really make the most of it. Maybe I'll try a WTB on black market and see if there's one out there that's cheaper than ebay.

 

[thecr4ne]

So I just cracked this thing open to have a decent look at what's going on. I now have more questions than I started with. Obviously this thing was modded to take the non-octal Triads, but it looks like they got a little too creative and made some stupid decisions along the way.

The octal sockets on for channels 1-3 were removed and the HS-1s attached to the chassis and soldered directly. Fine, all looks good, whatever. Octal socket for channel 4 appears in tact and original. Great. V1 and V2 sockets look as they should.

There's 4 RCA connectors, no longer soldered to anything, potentially an attempt at direct outs (I already know your feelings on that Doug)

Output transformer, Triad HS-50, is more or less where V4 should be. Actually covering the hole where the 9 pin socket for the 6CG7 should be. So where's V4?

...On the original output transformer's Octal socket...This is a bad idea right?

I didn't get any Octal tubes with this, so I'm at a loss as to what they were using for this, and I'm too much of a novice to make an educated guess based on what's here.

Heater wires are going to Pins 7 and 8, .22uF cap from V3 pin 1 is on V4 pin 4. Pin 1 is wired to pin 4,pin 2 to pin 5, and pin 3 to pin 6. Pin 2 is wired to the output transformer, Pin 6 goes to one of the big multi-caps, and pin 1 goes to ground through a 1M resistor. There's also a 1uF orange drop that's lifted on one end, the other end is on the output transformer with the wire from V4 pin 2.

If anyone can help me determine whether this is for a different tube, or if they were using acommon octal to 9-pin adapter and the 6CG7, please let me know.

Here's a pic.

 

[gridcurrent]

If anyone can help me determine whether this is for a different tube

wired for a 6SN7gt, triodes in parallel.
I've seen 1567a more kludged than your unit.
One from a famous "engineer, had Ouncers installed feeding custom transistor preamps, fed from an external supply.
Your HS-50 and HS-1 transformers are worth a small fortune.
I would keep those vintage pieces for some future project.
Meanwhile, as octal sockets and 15095's are readily available,  as are decent input transformers.
restore that mess as best you can and get it behind you.

 

[emrr]

Yup.  Good luck in the decision process. 

 

[thecr4ne]

Thanks for the input everyone. At least I have some idea of the state of things now. I have 2 other 1567A's in very good shape, with the full compliment of stock transformers, so I may just salvage the triads from this and try to sell the husk. With the going ebay price, I could probably make my money back, minimal effort.

I'll sit on it for a bit and think it over.

Would love any suggestions for projects to get the most out of the Triads

 

[thecr4ne]

I think I've found some direction. I've ordered a few sockets to replace the originals for the transformers and the 6CG7 and I'm planning to wire it back to stock and just sell it, sans transformers. I may even be able to recoup my initial investment, and I'll keep the nice pile of Iron. 

That said, I recently bought a pair of Altec M20 (165) mics with the 525a psus which, devastatingly, are missing the Peerless 4665's. Since I have them, I'll use the Triad HS-1's in their place. Specs seem to be pretty close, I'll just wire the Triads into octal plugs and see how things sound.

 

[Quayhog]

If you need some 4722 transformers to make your restoration complete I have collected several and I have enough to populate a 1567a.    I Collected these when I’d pickup Altec 348 PA amps and convert them into something more useful.