What's wrong with my twin?

Any ideas?

’73 or ’74 SF twin reverb with master volume, 100W.

First off, something’s wrong with the output. Last night I put master volume on 7 (channel volume on 8.5) with trem and reverb off and it should have blown me out of the house. Nope, it was bedroom level. EQ was 5 bass, 5 mid, 5 high. Tone was garbled/distorted on the low end – not tight, sounded like speakers were blown. Checked cones, they seemed fine.

I turned bass eq down to 3 and things were a lot better, tighter bass, but no balls. It seemed a little louder but still not like it should be. This amp used to be mighty fine – thumping bass on low 2 string double stops, clean, chimey tones and loud – you could lean against the sound.

What could it be? This is my main amp for gigging - bars/clubs - using an '80 ES-Artist, playing blues & classic rock.

I’m about to take it in and need some clues before talking to the tech.

I would, just for shits and giggles, hook up another cabinet and try it again. Then you've really eliminated the speakers. Plus, that's a fast check. After that, it's only time consuming troubleshooting that'll tell what the heck happened to your Twin. Unless you get lucky and it's just a tube.

I had the same thing happen to me a few times. Once, it turned out to be the battery was going dead in my Clapton Strat. The other time was the cord from my effects to the input had a resistive short and was droping the output from the guitar down too low for the amp to amplify. In both cases, it was a lack of signal going to the amplifiers input jack.

I'd try a new cord and different guitar as my first tests. If that fixes it, clean your guitar jack and cable... replace the cable if it's bad... Then, I'd look at cleaning the input jacks with an electronics cleaner/lube.

If you get that far and it still didn't work right, I'd try re-seating all of the tubes in their sockets... If all that didn't work... it's time for the amp doctor.

Good Luck with it!
jack

I would say you have a power tube(s) going bad. What you describe sounds an awful lot like that. How much playing time is on the tubes?

Thanks for the responses!

OK, I'll go through the steps to check for non-amp causes.

I do have a battery in my ES-Artist. Replaced the old one that read 8.89 volts (should have been fine at that level) with a new one at 9.21 volts.

I'll check cords, jacks, tube seating.

Sparrow1, I don't know the time on the tubes, probably 100 hours or more....

How do you test tube performance? Can you do it with a multi-meter? Other measuring devices?

scott your best bet is to pack it up and send it to me. the amp needs a nw home. part of my lifes purpose is to take musical gear that no longer feels at home and take it in. if in the future the gear wants to return "home" i will let it go.
i swear this is true.... yeah, that's the truth.
:stxrus
steve

Unfornutaley if you're not experienced there isn't a really easy way to check tubes. the best way and what most techs will probably do is swap them out for new ones and see if the problem goes away.

Since you say you have a preamp in the guitar you play. Replacing the battery in it is a good place to start also. A dead battery could casue some of the symptoms you explained. Shorted cables also. Like Cherokee Jack has stated.

What makes me jump to power tubes. I just recently and for the first time had a power tube go suddenly and quickly in a one of Mesa Boogies. It's pretty shocking. An amp is blasting away one day and the next day it's farting all over the place. It makes you think the worse. New tubes and all was well.

Hopefully it's something more simple.

Quote:

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Originally posted by stxrus
scott your best bet is to pack it up and send it to me. the amp needs a nw home. part of my lifes purpose is to take musical gear that no longer feels at home and take it in. if in the future the gear wants to return "home" i will let it go.
i swear this is true.... yeah, that's the truth.
:stxrus
steve

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Steve,

You're right, I didn't recognize it before. I'm such an idiot! How could I not have seen the truth?

The amp just wants a new home. OK, it's on its way!

Wait, before I ship it, I'm gonna have a little "conversation" behind the woodshed and might just whup its tolex butt - until it says it wants to stay with me. :whip Who's your daddy?

Yeah, that' the ticket. If that doesn't work, I'll email you the tracking number :lol2

Scott