Please help identify this old power amp

[Dave Johnson]

It's U.S. military surplus. Inspected and sealed in a heavy foil & paper package,in 1945. Three Sylvania 6L6GA coke bottles, a Sylvania 5U4G coke bottle, an RCA 6N7GT/G and a JAN Tungsol 6SJ7GT. Two recessed pots marked RFS & RS. The only number I have for it is 12994 Amplifier, off the inspection sheet.
Thanks, Dave

[J M Fahey]

WOW !!!!!!!!!!!!!!!!!!!!!!!!
POWERFUL MOJO !!!!!!!!!!!!!!!!!!!!!!!!!!
That's a beauty. For the odd shaped chassis it definitely was not designed to sit in a shelf but probably to make maximum use of some cramped military vehicle (or ship).
Maybe it was meant to drive a few multi-cell Altec horns and yell: "bomb/torpedo warning", "submerge", or simply "surrender you Japs/Krauts/etc."
Unless we have a 99 Y.O. WW2 veteran technician around, I guess you'll have the labor of love of tracing it.
Please don't rip it up just to build *another* 5E3, try to make it live and drive it with some external preamp.
Just my 2 cents.

[Dave Johnson]

I hear you, loud and clear! It's a time capsule and built like a tank. I would want to "call it into service" once again. I'm hoping to find more info on its original use. I have a few more off them to share with the world once I hunt down some facts. The only other clue I have is Red River Arsenal.

[overtone]

That is a really fine example of workmanship and from here I can see no signs of old age. It would be great to trace the circuit out and to very carefully bring it into service.

Recently I was struck by the ingenious and extremely high build quality of some Warsaw Pact military tube equipment that came my way. It was very chilling to hold and study a little piece of Cold War material, however insignificant it was. I was thinking "Respect".

Good luck with this one! tony

[Dave Johnson]

Thanks all, I have a couple more clues, but still no I.D... The official stock number from Red River Arsenal is F209-76-90896 amplifier assy. The other number I had 12994 was off an inspection sheet that was with the units. Just for kicks I put one on Ebay to see what would happen. If anyone wants to follow it... U.S. military surplus power amp / tube amp | eBay

[jmaf]

That is a beautiful piece. Judging by the L shape, it was likely the AF amplifer component of a military radio or some other equipment that it fit into, so perhaps there is no ID for it except its part number. Did you try powering it up?

[Dave Johnson]

I haven't tried to light one up yet. I wanted to find some more information first, but my curiosity is getting the better of me.

[jmaf]

I haven't tried to light one up yet. I wanted to find some more information first, but my curiosity is getting the better of me.

I wouldn't have waited 5 minutes! I'd start with a current limiter and variac, checking heater voltages, etc, until 6.3 VAC is found on the 6l6 heaters. Then check what the input voltage is, maybe it's not standard 120 VAC...

[Dave Johnson]

I found a number on the power transformer (8712), but it doesn't match up with the Chicago Transformer catalog from 1953 that I found on line. Untitled Normal Page. I suppose I'm just going to have to "just do it".

[Enzo]

Try contacting some people who deal with old military electronics. Send the information to perhaps Fair Radio Sales, and if they can;t help, askthem if they can suggest someone who would know.

[Dave Johnson]

Thanks Enzo, I did contact Fair Radio Sales. They couldn't help with I.D. They did inquire on the weight and where they would be shipping from. But I haven't heard back.
My curiosity finally got the better of me, I fired one up today... No smoke, no fire. Got it to pass a signal, but the hum was pretty bad. I'm thinking the filter caps have dried up from sitting untouched for 65 years. Fired a second one up, hum wasn't as bad but was still present. Kind of neat bringing something from WW II back to life after all this time.

[Gtr_tech]

Oh gawd yes. All the lytics are trashed from sitting unused. I'd replace all the coupling caps as well as they're prob'ly paper/oil types. Those don't weather time well at all.