Transformers Triad, Thordarson ??

[rokker]

So I was given a couple old tube PA power amps... not sure exactly what they are yet. No writing on the exterior of the chassis. The tube setup is 2 x 12au7, 2 x 6l6s and a 5u4. The only writing was on the inside of the chassis where someone wrote by hand some model #s about the transformers:

PT
Triad
HS-207
GR-1 CLA Family 03
700v @ 120ma

OT
Thordarson
T-52408-A

I read a few places that old fender transformers were made by Triad? Is this true? I dont know anything about them or Thordarson. Does anyone have any info on these?

Thanks

[jazbo8]

TRIAD-HS-207

Thordarson-T-52408

[rokker]

Thanks, yeah I saw the listings on ebay. Just wondering if anyone has any experience with them etc.

[DummyLoad]

I read a few places that old fender transformers were made by Triad?

early stuff from what i've seen in pics only - mostly tweed and some brown face. all the blackface and silvers i have seen seem tho have woodward-schumacher (EIA 606) iron.

--pete

[eleventeen]

Classic American iron....like a '55 Chevy. Both are good quality brands, not much more to say. I have found that those nice grey Triads, unless they are sort of oversize, seem to have lowish HV current ratings. Meaning, a tranny that you'd think (judging by size) would be rated for 100-120 ma (per the print on the end bell) is only rated for 75-80 ma. Perhaps that is a conservative rating approach by the mfr...perhaps it is the true truth. I know they fetch good prices on ebay because....wait for it.....they are painted GREY!

[HotBluePlates]

PT
Triad
HS-207
GR-1 CLA Family 03
700v @ 120ma

Very likely the Triad HSM-207, especially if it's in a sealed can.

Can be found on page 7 of the 63-64 Triad Catalog. 700v CT (350-0-350v) @ 120mA, 6.3v @ 5A, 5v @ 3A.

OT
Thordarson
T-52408-A

I'm having trouble finding any Thordarson catalog newer than 1947. It seems many like the nostalgia of the older catalogs. However, based on pictures you probably already know this is a 6.5kΩ primary, 8Ω secondary (with an extra 500Ω line secondary). Power rating uncertain, but given everyone seems to mention a pair of 6L6's, you're probably safe assuming 30w.

If I had a pair of these PA amps, I'd probably use them to power speaker for a home stereo. Alternatively, you could build a small preamp unit to go between your guitar and the PA; add a speaker and you've got an amp.

[rokker]

Thanks for all the info.

Ill get a pic of the chassis and transformers tonight but yes they are both in the sealed cans but are black.

I was thinking of using them for a 6l6 build... Oh and both the chassis had RCA 6l6s in them but I have not tried them yet. Hopefully they are still good.

[DummyLoad]

...any Thordarson catalog newer than 1947

http://www.tubebooks.org/transformer_data.htm

65MB

--pete

[HotBluePlates]

I was thinking of using them for a 6l6 build... Oh and both the chassis had RCA 6l6s in them but I have not tried them yet. Hopefully they are still good.

The RCA's are likely still good.

I strongly suggest you do not remove the transformers for use in something else. As is, they are already being used in a "6L6 build".

What you have is essentially a guitar amp minus the preamp in each of your PA amps. Actually, depending on how they were built, they may have a preamp; would need a photo of the outside/inside to guess that.

So you do not need to yank the transformers out and rebuild; in fact, you'd just have to recreate/re-engineer exactly what they have now in the way of a power supply and inverter. So the best and least-painful way to proceed (least expensive, too) is to determine what you need in the way of a preamp and build just that to interface with the existing power amps.

This recommendation is based on the high volume of posts we've seen with questions about how to use a transformer set salvaged from some piece of tube gear. Ultimately, the person asking the wuestion finds they have to re-use them exactly how they were used in the piece of gear they were taken from.

Same as if I salvaged a Porsche 986 engine and wanted to use it in a Honda Civic chassis. Doesn't exactly work, and ultimately I need to build a DIY-Porsche around the salvage engine.

[rokker]

I was thinking of using them for a 6l6 build... Oh and both the chassis had RCA 6l6s in them but I have not tried them yet. Hopefully they are still good.

The RCA's are likely still good.

I strongly suggest you do not remove the transformers for use in something else. As is, they are already being used in a "6L6 build".

What you have is essentially a guitar amp minus the preamp in each of your PA amps. Actually, depending on how they were built, they may have a preamp; would need a photo of the outside/inside to guess that.

So you do not need to yank the transformers out and rebuild; in fact, you'd just have to recreate/re-engineer exactly what they have now in the way of a power supply and inverter. So the best and least-painful way to proceed (least expensive, too) is to determine what you need in the way of a preamp and build just that to interface with the existing power amps.

This recommendation is based on the high volume of posts we've seen with questions about how to use a transformer set salvaged from some piece of tube gear. Ultimately, the person asking the wuestion finds they have to re-use them exactly how they were used in the piece of gear they were taken from.

Same as if I salvaged a Porsche 986 engine and wanted to use it in a Honda Civic chassis. Doesn't exactly work, and ultimately I need to build a DIY-Porsche around the salvage engine.

Yeah I thought about it for a minute and thought the same thing, why remove them? I can just use the existing setup and modify it.

[HotBluePlates]

Good call. I only warn you because I've already made that same mistake.  

[PRR]

> 2 x 12au7, 2 x 6l6s

And just one line-level input?

Then it is a simplified Williamson. Gain stage, cathodyne, push-pull gain stage, push-pull power bottles.

While this *has* been done as the final stages of a guitar amp, simpler power-blocks are more commonly loved. Find a 2*12AX7+2*6L6 guitar-amp plan. The wiring around the power supply, OT, and 6L6 plates can be UN-changed (and UN-touched). Just re-wire the little sockets, add jack and knobs.
________________________

Both Triad and Thordarson were MAJOR players in the iron racket, including the retail market, usually excellent quality. While Fender may have used either or both in some model runs, he had enough volume to get custom winds from competing factories to push cost down. There's several iron houses who don't push to retail market.

The transformers are fine until you find out otherwise. (They are old enough for age-related failure, or may have been brutally abused in a past life.)

[DummyLoad]

Good cal. I only warn you because I've already made that same mistake. 

ditto!   

/fortunately i keep a spare set of feathers for just such an occasion/

--pete

[rokker]

Here are a couple pics. I stuck an ac30 PT next to the chassis for comparisons sake. The exterior is dirty but the guts are still pretty clean.

[PRR]

Wow. It's clearly a Heathkit but never came from Heath, someone put-together with stray parts.

[rokker]

So what do you guys think I should do with them? I could add 1 or 2 more 9pin sockets, and some pots ( this doesnt have any ) to the existing chassis. Or I could make a seperate pre-amp chassis and this could be the power amp????

[DummyLoad]

for reference: heathkit A-9c i butchered near 2 years past... sold it for 60 bux just to get it out the house. guitar player for a band called whiskey logic bought it. he loved the tone and said he used it on a couple of songs on the bands only album he played on; never did get a straight answer on which ones.

link to A-9c thread:
http://www.el34world.com/Forum/index.php?topic=11814.msg109538;topicseen#msg109538

if i had it to do all over again, i'd lose the DC PS for the pre tube filaments; it does all fit. you have two chokes. you don't need two chokes?

as already numerously stated; suggest you reverse engineer at least the power supply and the output stage. at least so you have some reference to go back to, just in case. also, may i suggest taking an obscene number of hi-res. closeup pics as well.

scrap the rest?

--pete

[HotBluePlates]

So what do you guys think I should do with them? I could add 1 or 2 more 9pin sockets, and some pots ( this doesnt have any ) to the existing chassis. Or I could make a seperate pre-amp chassis and this could be the power amp????

Take some pictures of the sides, especially where there's an octal socket on the side.

I believe this thing is like a lot of hi-fi (not PA) power amps of the time, and includes an octal socket which is a power outlet for the preamp. That means there will very likely be 6.3v a.c. between 2 of the pins, a ground connection, a high voltage connection (perhaps 300-350v) and a signal connection.

Then all you need is a preamp chassis with a corresponding octal socket to use as an umbilical connecting the two. If you're really concerned about safety, you'll simply arrange the umbilical like any other power cord, and not have it detachable at the preamp chassis. That would ensure you can't plug into the power amp and have exposed pins with high voltage at the other end of the cord.

You may also have signal inputs on the barrier strip, or the RCA jacks I think I see.

[PRR]

> what do you guys think I should do

Find a 2*12AX7+2*6L6 guitar-amp plan. The wiring around the power supply, OT, and 6L6 plates can be UN-changed (and UN-touched). Just re-wire the little sockets, add jack and knobs.

[rokker]

Couple better quality pics.

[DummyLoad]

document it, salvage the iron, scrap the chassis. poor layout - not conducive to guitar amp.

--pete