Did I fry my output transformer?

[theculprit]

What up dudes, bad day to be an amp

About a year ago, I bought a Randall RG100ES. While testing it, I accidentally connected the speaker output of the Randall to the speaker output of my Peavey Triple X. Although the Triple X was off at the time, I assume it still took the load, especially since I had the Randall cranked to max volume. It never occurred to me at the time that I may have damaged the amp so I never turned it on to check.

Fast forward to now, after not using the Triple X for almost a year, its volume is very low, and the tone is thin and lacking gain. I did the "tap test" on the tubes and found that one of the preamp tubes was coming through the speaker. Thinking I may have damaged the preamp tubes, I replaced all of them with a new set. Unfortunately, the amp is still in the same state and the preamp tubes made no difference.

I thought it maybe the power tubes, but I spoke with a local amp tech and he thinks it's the "damper" diodes in the Triple X. Unfortunately, he's out of town and won't be back for another week.

Any idea what could have happened? I do have a multimeter on hand, but I'm not sure where to even start.

[mikeydee77]

I don't automatically think that connecting the two amps together would damage either one. presumably you weren't paying for long? The signal into the peavey is just going in backwards but voltage levels would be in line with norms. Definitely not recommended practice. Interested to hear what others say on that.

With the low output you need to isolate if it bad preamp or power amp first. Is there an FX loop on the amp where you can listen to the preamp? And inject your guitar into the power amp. it will be a little quiet but hopefully clean confirming that the power amp is OK including the output transformer.

[Jon Snell]

Cr100 & CR103, damper diodes, when fail, fail short circuit. That will take the HT fuse out at power up and give no sound at all.
Probably needs some TLC to get it working properly again and just coincidence that it is not as sweet sounding as the Randall.

[Helmholtz]

.Please post ot link both schematics

[R.G.]

As a general comment, it's very common to see questions saying much the same thing: " I did [something] and now my amp [is way different]. It's the output transformer, isn't it?"

The general answer to this kind of question is "Well, maybe. But transformers are pretty darned tough. It's best to eliminate the other things first, like tubes, catch diodes, arc traces on the output tube sockets, and so on before deciding it's the OT."

It's possible to just test the OT by disconnecting all the leads and running ohmmeter tests for continuity and shorts, then running the pulse-inductance test with a battery and a neon bulb.

[Chuck H]

As a general comment, it's very common to see questions saying much the same thing: " I did [something] and now my amp [is way different]. It's the output transformer, isn't it?"

The general answer to this kind of question is "Well, maybe. But transformers are pretty darned tough. It's best to eliminate the other things first, like tubes, catch diodes, arc traces on the output tube sockets, and so on before deciding it's the OT."

It's possible to just test the OT by disconnecting all the leads and running ohmmeter tests for continuity and shorts, then running the pulse-inductance test with a battery and a neon bulb.

Haha!!! Yours is the first description for and you are the first proponent for the neon bulb test for OT's here. So there's no way you wouldn't post this. That said... As general and gentle as your post is I think you may have just blown up the OP's brain. I apologize to the OP it they are offended but "I do have a multimeter on hand, but I'm not sure where to even start..." might indicate a skill level requiring even more general terminology and a walk through any processes. I hadn't posted because I think their best bet is to wait for their tech to look at it.?.

[Chuck H]

IMHE the problem with your Peavey could well be neglected and corroded contacts. Take some time to use peoper products and clean every accessible non soldered contact in the amp. This site is chock full of good info about how to do this with a little searching. Nothing to be lost in the effort.

[R.G.]

I apologize to the OP it they are offended but "I do have a multimeter on hand, but I'm not sure where to even start..." might indicate a skill level requiring even more general terminology and a walk through any processes. I hadn't posted because I think their best bet is to wait for their tech to look at it.?.

You're right, Chuck. That sentence should have triggered a different message number.

@ OP: It is difficult to tell from your post, but unless you are sure you already know how to work safely inside an AC powered device, you probably should get a tech to look at it for you. The insides of a tube amp can retain hazardous voltages, even after the power switch is turned off, and even for a while after being unplugged. Developing the skills to work in mains powered electronics is difficult to do, and not something to do by reading the internet. Remember: no amp is worth dying for.

If you already have these skills, and just don't know about how to debug a suspected transformer issue, that's a different matter. My post was more suited to this possibility. Chuck's comment is good advice; contacts are always suspect, always, and don't require risking electrocution in most cases. Your instinct to try new tubes was also good; there is a reason they are in sockets and not soldered in. Your tech friend's idea is a possibility; those diodes take a lot of punishment when an amp is pushed with no load.

For reference, you might want to read the Tube Amp Debugging Page here: http://www.geofex.com/ampdbug/ampdebug.htm It reflects my state of knowledge about the debugging process as I knew it 27 years ago. I really should re-write that and include some things I've learned since, like Chuck's advice on contacts. But it gets you a good order of suspicion.

[Chuck H]

The OP indicates that the amp was shelved untested for a year after the aformentioned incorrect connection. So I thought it was at least possible that contacts could have oxidized with age. We see it here a lot... "My amp has been sitting for a year and now it doesn't work right." The first thing I usually suspect in these circumstances is oxidized contacts. Of course having put a signal backward through the OT could have had consequenses for the protection diodes so that would be the next thing. If you know what you're looking for you can probably rule out the OT itself pretty quickly with a multi meter. I also don't suspect the OT but testing for expected resistances and shorts could put the OP's mind at ease?

[Chuck H]

Interestingly the OP hasn't been back since starting the thread.

[glebert]

Simplest (and safest) test I would recommend is plugging a guitar directly into effect loop return jack (with the effects loop engaged). This should eliminate a fair amount of the tubes and also the contacts. Should hear clear sound, though maybe not very loud. If that sounds good the OT and "damper" aka flyback diodes should be fine.

[glebert]

Interestingly the OP hasn't been back since starting the thread.

Well, at least they gave us something to talk about for a bit.

[g1]

Interestingly the OP hasn't been back since starting the thread.

OP has posted this question on at least 3 other forums, plus reddit. Maybe getting more action elsewhere.

[R.G.]

Hmmm. You think averaging raw internet responses makes for a better answer??

[Chuck H]

For people that know the difference staying here makes for the better answer