http://imageshack.us/photo/my-images/4/triomatic.png/

http://imageshack.us/photo/my-images/31/triomatic2.png/

The damage is visible in the first image.

From what I've learned, and what you guys will already know looking at the photo, it was the output transformer that got fried, after all... there's no apparent damage inside, though I need to go in with a VOM to make sure. In the meantime, I'll probably go ahead with a cap job.... Any ideas on the transformer?

Obviously, burning the flat down during a session of Brubeck's Brandenberg Gates is not a possibility I'd like to consider, so new caps are on order tonight for the motorola, which will rest until then.... thanks for the sound advice.

Nice and clear. Nothing wrong with THAT chassis!

-David

That is pretty spectacular frying of an output transformer No worries, they are pretty easy to come by. Is there a model number on this thing? What tubes does it have in it?

You see those 4 waxy tubular things on the underside and that one great big tubular thing. Those are all capacitors. One of the little ones being shorted probably cost you the transformer. The big guy, if not already failing will fail. It's just a matter of when.

Those and anything that looks like them need to be replaced and then we probably need to find you an audio output transformer. I'm pretty doubtful that one survived.

Curtis Eickerman

I'm not sure a fried output transformer would cause such spectacular fireworks including taking down a 15A branch circuit. Seems to me that there would be very heavy damage to the rectifier, series resistors, etc., that would protect the branch circuit and contain the damage.

-David

Good point, but that sure looks like where all the fireworks took place. It would take out a branch circuit if the chassis was not isolated from the outside world and was sitting on something grounded. Not sure how that would make fireworks come from the audio output transformer though.

Curtis Eickerman

What is the tube set up...looks like a 12AV6 and a 50C5 maybe? So should be a two stage amp. If so I have a couple spare OT and would just send you one free that will work for you if you are in the USA. Only thing I think you are over the pond by the "burn down the flat" comment.

T

I don't know if it's clear to David, but it sure is clear to me!

I pulled the schematic and this amp uses a 12AV6, 50C5, and a selenium rectifier. These rectifiers can go up in smoke and smell like rotten eggs. There's a good chance it was damaged when the output transformer shorted and it should be replaced with a modern 1N4007 diode. Since the silicon diode has less voltage drop than a selenium, you may wish to increse the AC input resistor from 33 ohms to something in the 68 ohm range.

Go ahead and replace all capacitors and carefully check for any wiring with faulty insulation or bare component leads that are touching something. Once the rectifier, caps, transformer, and any faulty wiring have been taken care of; you should be safe to plug the unit into either a variac or dim bulb tester. If the bulb remains dim or if the current draw remains low, you should be safe in applying full power. And, just for good measure, replace the 50C5 output tube just in case it was damaged when the transformer failed.

Well said. By the way, have you been able to establish which 1953 model number this is? I was looking and found VM turned out 10 or more at the time and I am not sure which one it might be. I had no luck locating a freely available schematic myself.

I see radiotvnut seems to have a schematic which would be very helpful.

The amplifier doesn't look too complicated so it may be possible to do the necessary repairs without documentation, but lack of information usually makes things a little harder.

Curtis Eickerman

I don't see where repairing this unit is a problem at all.
I'm sure Gary Stork of www.thevoiceofmusic.com has all the parts and info needed for the job.

After all, he bought out the whole warehouse of VM inventory to utilize for such things.

Good advice, RepairTech... as it happens, Gary emailed me back. While he had the schematic and part # for the fried transformer, he doesn't actually have the individual component on hand. Radiotvnut, Eikerman, and others have both given me more than enough info for a solid foundation in getting this unit up and running again. In the meantime, you were right... I did learn... a lot. Thanks for the help and support guys.

I posted this a while back, not sure you saw it. I have a bunch of good out put transformers for your amp and you can just have one for free. Other then the OT everything else is your amp is easily and cheaply replaceable. If you want one of these OTs you can have it and then the rest is easy to go through. This is a tiny little amp...with a correct OT you could build another identical amp from $10 worth of new parts.

Oh, it was clear to me. See my post of March 04.

-David

Please do not connect any phonograph to a dim-bulb tester or to a Variac unless the motor can be turned off or disconnected. Induction motors can be burned out by trying to operate them at less than their rated voltage. It causes them to draw far too much current. For an induction motor, high voltage is better than low.

-David

I just cleaned out a relatives attic that passed away, and found a triomatic model 556a. it seems to work fine, contact me & maybe we can work something out.

Sorry, but if you're selling something, it goes on the classified thread with a posted price.
Rules.