Ampeg SVT-CL standby light flashing red/green

micahturner · #1 02-26-2011, 09:07 AM

I fired up my SVT this morning and my amp made a fart sound and soon after I noticed what smelled like electronics burning. The Standby/power light was flashing red to green and the red bias light was lit as well. Any ideas before I dish out the cash for a tech?

Thanks

jastacey · #2 02-26-2011, 10:20 AM

I could be anything ...... take it to a tech

BassmanPaul · #3 02-26-2011, 10:59 AM

Agreed! The life you save could be your own.

T-Bird · #4 02-26-2011, 11:38 AM

Hi.

Quote:

Originally Posted by micahturner

Any ideas before I dish out the cash for a tech?

Don't try to repair or diagnose it by Yourself.

Unfortunately Paul nailed it, the zap may be Your last. Or at least leave a bad mark.

Regards
Sam

craig.p · #5 02-26-2011, 11:59 AM

I agree with all the above, but I just wanted to ask whether this thing smoked right after having been transported.

micahturner · #6 02-26-2011, 12:05 PM

No smoke. Its been sitting in the house for about a week and I've played it since its last transport.

Thanks guys, off to the tech.

micahturner · #7 03-08-2011, 09:00 AM

Heard back from the tech. It's not the tubes so he is continuing to work on it, very slowly. Any ideas?

Grooveman1961 · #8 03-08-2011, 12:03 PM

Quote:

Originally Posted by micahturner

Heard back from the tech. It's not the tubes so he is continuing to work on it, very slowly. Any ideas?

I bet your tech finds that one or more of the screen resistors is fried,and that one of the tubes has a tendency to flash over.

micahturner · #9 03-09-2011, 07:09 AM

Heard back from the tech yesterday. Three of the plate resistors had blown and he suggested that I replace all the power tubes. The amp still had the original Sovtek 6550's so I'm upgrading to a sextet of Tung-Sols. My question to you guys is this; would it be a good time to change out the preamp tubes? I am leaving for a long string of shows next week and I do not want to run into any more bumps in the road since this is my only amp.

Your input is always appreciated.

craig.p · #10 03-09-2011, 07:52 AM

If it were my amp, and if I were happy with the sound, I'd leave the preamp tubes alone.

micahturner · #11 03-09-2011, 08:01 AM

Sound advise. Thank you.

jaywa · #12 03-09-2011, 08:04 AM

Quote:

Originally Posted by micahturner

Heard back from the tech yesterday. Three of the plate resistors had blown

That doesn't sound like something that just happens with age. Was there a funky situation with the power or anything at the last gig you played?

Not that it matters now but maybe there's something that can be done to keep it from happening again.

beans-on-toast · #13 03-09-2011, 08:18 AM

Quote:

Originally Posted by micahturner

I'm upgrading to a sextet of Tung-Sols. My question to you guys is this; would it be a good time to change out the preamp tubes? I am leaving for a long string of shows next week and I do not want to run into any more bumps in the road since this is my only amp.

A new set of tubes can also be a bit risky. New tubes can blow if they have a fault in them. Fortunately, if a tube is going to blow, it will do it soon after installation. Some places sell tubes that have not only been tested but are also burnt in for some period of time, typically 24 or 48 hours. You pay more but if reliability is important, it is worth the investment.

I would change whatever tubes you are going to change. Then make sure they are burnt in by using them as much as you can before hitting the road.

craig.p · #14 03-09-2011, 09:03 AM

I think that amp uses half of a 12BH7 to bias one bank of three tubes, and half of another 12BH7 to bias the second bank of three. Maybe half of one 12BH7 crapped its pants and allowed one bank to run away, until the plate resistors saved the day by opening up? Maybe an SVT/tube heavy will pop in and say whether that's even a possible failure scenario. (Hell, I might even have the topology wrong...)

Might have to withdraw my recommendation about not replacing any preamp tubes. But let's see what the folks who really know SVTs have to say.

micahturner · #15 03-09-2011, 09:18 AM

I'm not sure if they have been burnt in. I'm buying them from the tube store and the tech is doing the install and biasing. No strange power issues at my last gig that I know of. I'm not knowledgeable about the technical side of tube amps. I just know that they sound great and they have the capacity to kill you.

micahturner · #16 03-12-2011, 01:30 PM

Got my SVT back from the tech. He replaced the 2k plate resistors with 5k plate resistors and retubed the power section with Tung Sol 6550's. The head sounds amazing, and he told me that I should have nothing to worry about when I take it out on the road for my upcoming tour.

coreyfyfe · #17 03-12-2011, 04:13 PM

Quote:

Originally Posted by craig.p

I think that amp uses half of a 12BH7...

If it's an SVT-CL it uses 12AU7s. Either way, you should be fine with what you have in there.

micahturner · #18 03-12-2011, 05:21 PM

I asked the tech if I should replace the preamp tubes and he said that they had tested strong. The preamp tubes are 12AU7's(I think) or maybe the 12AX7. He told me that there was no reason to replace them. He also said that the 2k resistor was of poor quality and should be replaced anyway.

I don't know. My amp works and sounds great, so I'll take his word for it. It's all greek to me.

Killface · #19 12-18-2011, 12:35 AM

I went to GC yesterday and seen an ampeg svt classic and got excited to try it out "with an 810 stack" because all I've heard was good things. The dude plugged it up and turned it on and this same red/green thing was going on. Needless to say I was disappointed. Man I wanted to hear this baby sing! ***! So I tryed an ampeg amp with preamp tubes. I still like my tnt for the tuff as nails quality but man I wanted to try the svt!