"Dorothy, the Evil Twin Is Dead!"

[phfobric]

Want to know if this sounds like something I could do or I have to sub-out. I do have the schematics.

This early 90's Evil Twin (yes, the one in the thumbnail), the BEST of 'em all, IMHFO (...except for it not running now...) was fine at last rehearsal. Today when I turned it on, the standby switch was in GO MAN mode (we do it at the bass player's house, with kids, not a prob usually), something I don't do. Been a Fender man my whole life; you let the tubes chill a bit after a workout, before shut down. Everytime

It appeared to warm up, hit a chord in the hi-gain section and played a couple of clean chords, then we talked about what we're going play, yada yada and then, there ain't a peep coming out of the amp now, all of a sudden. Noticed the 6L6s were dim and not HOT, the 12AX7s were toasty. If you were facing into the amp from behind, the output (?) transformer on the left was TOASTY, but the one on the right was tepid. Not a peep. Even dim, there was no change when I played a little while we watched the tubes for any something!?!

Power light comes on, fuse okeh, no smell of any burning sensation at the time. What's a mutha to do? Any and all takes appreciated in advance. I love this "effin'" amp. Need another (cheaper by the dozen, right?) I know when I'm going to have to cave, but if I can do it, I can do it now. It could be weeks before I see it if I shop it.

[Enzo]

Turning on the power with the standby already on won;t hurt the amp or the tubes. And even if it did the stuff people worry about, it wouldn;t affect the heaters inside the tubes.

So it worked OK, then a little while later it was silent, right?

Remember, the voltages inside the amp when it is running can KILL YOU.

And never turn it on without a speaker plugged into the main speaker jack.

Look in the rear and see if the speaker plug is partially or completely pulled out of the jack. And if it is in, make sure it is in the main speaker jack and not the extension speaker jack.

And using either a 9v battery or some other amp, test the speakers and their cord.

You can measure the AC voltage between pins 2 and 7 on the power tube sockets to see if it is getting there. That is the heater voltage.

We can also check for B+ voltage (450-500V DC) on pins 3 and 4 of the power tubes. B+ needs to get to all the tubes for that matter. B+ shows up on the terminals of the standby switch for a quick check too.

I doubt bias is an issue, either it is present, or too high (which would result in sterile sound, not silence), or too low or missing (which would still be loud, but your tubes would be melting).

It is normal for the power transformer to get warm - the one closest to the power cord. The output transformer usually won;t warm up as much, and not anyway until you have been playing through the amp a while.

[phfobric]

Thanks for the speedy response!

The speaker jack "thing" is well-known. I was using a 4-12" cab wired series/parallel to 8 ohms to the main out (amp switched to same ohms), not using the Twin's own 2-12"s. There is far more ambiance/headroom in the guitar sound this way. Been rehearsing, and gigging with it in this config for months.

After no sound from the Twin, OC (our bassist) rolled out another amp and using the same (Monster) speaker cable, and cabinet, we completed rehearsing.

Some of the tests you describe must be done with the chassis out, no?, and the amp ON? That automatically puts me out of the running. I don't have a jig to set the chassis in, safely. And dying is not an option.

Perhaps you could point me to an amplifier "primer". There must be thousands, but maybe you have a favorite? OC was/is a Techie, more than me, but solving this is beyond our normal ability. We've set up many different/size PA systems through the years, and how to get the necessary tweakage for optimum sound, but that's more "outside", and the Twin is obviously an "inside" job.

I lost the gain channel, once, and when I had it shopped, Paul at Wells Electronics, here, in Orlando, just cleaned the dust out of the chassis and gave it back. I can definitely pull it, and check for that. Pin numbers (would my bank account pin number work? Sorry! ) are not a given for me. I don't know something, but I know there's a "key" in the center post of tubes and I reckon "1" must start on one side or the other, of the key.

Of the two available wattage options, I was on the 25w, 1/4 power option, if it makes a difference. Perhaps I shoulda, woulda, coulda flipped it to the FULL POWER option. I'll do that before any chassis pulling.

Dangerous, ain't I? (what a maroon!)

[Euthymia]

Perhaps you could point me to an amplifier "primer". There must be thousands, but maybe you have a favorite?

Tube Amplifier Debugging Page

[phfobric]

Sweet! Just what you (I, really) need to know when you need it. No B/S for real-time solutions. Cut to the chase. A bazillion Somolians and

74 (mostly) virgins for you in your next life! Enjoy