Will an OT still work if it's bad?

[mike80]

I'm getting very low volume from the amp on my Hammond M103. I've tried changing all the tubes (save for the power tubes) with no luck. I'm going in the morning to get another set of power tubes.

I bought a Leslie 125 this morning to hook up to it, and after I went thorugh the procedure and hooked up the Leslie the volume was very low. I unhooked everything and put it back to stock, but that didn't help anything. All functions work as they should, just the volume is barely audible.

To be fair, I haven't turned the organ on in a few days, so the problem could have existed prior to hooking up the Leslie cab..like when I pulled it out from the wall or something. I'm just wondering if I could have blown the OT while I was turning the console on to find AC power. I had the speakers hooked up to the Leslie hookup kit and the dummy load was installed in the Leslie cab while I was finding power. I don't really think that could have been the problem, but you never know.

[mike80]

Well, I changed the 6V6s with no change in volume. I'm starting to think the OT is fried. :(

EDIT:

I ended up smacking the OT with the handle of my screwdriver and the issue resolved itself. :dunno

[donnyjaguar]

It sounds like it arc'ed inside. Don't be too gutted if the volume drops again.

[mike80]

I figured it had to be something with the OT since everything still worked like it should, just at an extremely low volume and sounded weak. I noticed now that when I power the organ on I get distortion through the speakers until the tubes warm up.

I'm going to try to find a replacement and swap it out soon.

[SatelliteAmps]

An OT that shorts will still produce sound, just low volume and thin sounding.

[mike80]

An OT that shorts will still produce sound, just low volume and thin sounding.

That's what I assumed. I've never encountered a bad/shorted/blown OT before, so I wasn't exactly sure if that was what it could be. I read how to test them on a website, but I don't have the tools to do the test here at the moment.

After pulling every tube in the amp to verify it's function, swapping every tube, inspecting the amp and looking the block diagram, I concluded everything pointed to the OT. Since everything was working like it should, I narrowed it down to the OT or the speakers since those are the last in the line. The probability of 2 speakers being blown or both producing low volume didn't settle well with me, so I was pointing to the OT.

[MKB]

An OT that shorts will still produce sound, just low volume and thin sounding.
I haven't seen many blown OT's in my 30 years of amp repair, they seem to be fairly rugged devices. But I did see one Bandmaster that sounded very thin and anemic, and I assumed it was the OT. I didn't measure any of the parameters to see if it was good or not. If you were so inclined and had the equipment and time, you could make some measurements to determine the turns ratio and if the primary halves are balanced, that and a little math might tell you if it's good or not.

Most bad OT's I've seen short the primary to the core, which basically causes the HT fuse to blow immediately.

[SatelliteAmps]

I've seen five blown output transformers this month. All had the same sound issues. All related to playing through a cabinet with a blown speaker.

[StompBoxBlues]

I've seen five blown output transformers this month. All had the same sound issues. All related to playing through a cabinet with a blown speaker.


Wow...you'da thought the guy would have learned after the second blown amp and stopped using that cabinet :rolleyes:


("a woman gives birth every 5 seconds on this planet" "she must be very tired")

Seriously, this is interesting.

[SatelliteAmps]

5 different guys. Also one blown PT. Guy blew a tube, and rather than changing tubes, just kept putting bigger fuses in. Amp needed a 2.5a. The guy called me once he reached 10a.