A Little SVT Technical Help Please

Boss302 · #1 09-14-2011, 06:25 PM

I'm a proud, year-long owner of an SVT-CL but she's out of commission.

Problems started when I was given bad power at a gig and I flipped it on with a pop and a severe lack of volume. Everything looked fine though on the amp. So I used my little Eden Traveler to get through that gig. (Lesson learned, buy a power conditioner.)

After that, it works for a few days, no problems, but then I go to turn it on again and standby is fine, but when I switch out of standby, I get a large pop, too large to be normal, and a flash from the back and no sound, indicator light flashing red to green. I unplug and take a look in the back. One of the 6550's is visibly spent.

My questions to you guys:

Are these two instances related?
I suspect that I only need a tube-change but am I wrong?
If I need tubes changed, I'm going to need some help there with how to go about it the right way.
Bigger Problem = $&@%.

And what's the deal with people and repairing the SVT? None of my local places, even the guy who specializes in fixing tube amps will even look at it for me.

TL;DR: SVT-CL pops, tubes flash, no sound upon switching out of standby, what do?

Thanks

Rockmusician · #2 09-14-2011, 06:27 PM

Ampeg's website has a link where you can search for authorized service centers.

Service Center Locator

Boss302 · #3 09-14-2011, 06:33 PM

Quote:

Originally Posted by Rockmusician

Ampeg's website has a link where you can search for authorized service centers.

Service Center Locator

Nearest is 100 miles away... ಠ_ಠ

coreyfyfe · #4 09-14-2011, 07:02 PM

Could just be a bad tube. The red and green flashing means there is a fault in the power section, could be a bad component, or - given that a tube is out - it could be a bad tube. You could try swapping out a good tube and see if it works again, but I'd say your best bet is to find a tech that will work on it in case whatever you do makes the problem worse. Where are you located? There is a thread in the amps FAQ called "good amp techs", hopefully there is a recommendation there for someone in your area.

4StringShooter · #5 09-14-2011, 07:47 PM

Tubes are only replaced in PAIRS. I replaced all of mine, price? $250.00 CAN.
Have it biased by a Pro, you WONT regret it. Also have him check the GROUND WIRES to the Power Tube banks. Mine had bad solder joints.

coreyfyfe · #6 09-14-2011, 07:59 PM

Quote:

Originally Posted by 4StringShooter

Tubes are only replaced in PAIRS. I replaced all of mine, price? $250.00 CAN.
Have it biased by a Pro, you WONT regret it. Also have him check the GROUND WIRES to the Power Tube banks. Mine had bad solder joints.

In an SVT they're replaced in triads.

JimmyM · #7 09-14-2011, 08:05 PM

Ya, triads, and I'd never replace all my power tubes just because of one bad one. Ideally I'd like to find one that matches the other two, but that's not always possible, so at the most I'd only replace 3. If a tube ain't broke, I don't fix it.

**B-string** · #8 09-14-2011, 08:22 PM

Could be just the one tube but replace its mate as well. Chances are good it was the dodgy power that contributed to its failure, but it was destined to. The real question is did the tube take out a cathode resistor or screen resistor? That only a tech can tell you. You can try a pair at your own risk, it may pay off.

Boss302 · #9 09-14-2011, 08:55 PM

Quote:

Originally Posted by JimmyM

Ya, triads, and I'd never replace all my power tubes just because of one bad one. Ideally I'd like to find one that matches the other two, but that's not always possible, so at the most I'd only replace 3. If a tube ain't broke, I don't fix it.

Okay, they're the original tubes. Do they sell them loaded with a matched sextet or with two matched triads? If they're triads, is the front row one set and the back row another?

**Lazarus.Bird** · #10 09-14-2011, 09:01 PM

Can't believe none of your local techs will look at it. Last time I got the flashing power fault LED only 1 tube needed replaced. There's gotta be someone near you that can look at it.

JimmyM · #11 09-14-2011, 09:06 PM

Quote:

Originally Posted by Boss302

Okay, they're the original tubes. Do they sell them loaded with a matched sextet or with two matched triads? If they're triads, is the front row one set and the back row another?

They may sell them with a matched sextet, but they're two sets of matched triads, and are able to be biased separately so matching all six isn't necessary. And yes, the front row is one set and the back another.

beans-on-toast · #12 09-14-2011, 09:07 PM

If you are replacing all the power tubes, you normally buy a matched sextet. Each row of three is a set.

It is possible that the first event damaged your amp which let to the second problem. The amp just needed the right conditions to trigger the failure.

It is possible that something else has blown. Maybe a plate or screen resistor connected to a power tube. In a case like this it is best to have a tech examine the amp before any new tubes are installed and the amp is re-biased and balanced.

Jerrold Tiers · #13 09-15-2011, 10:10 PM

The SVT is fairly tolerant of bad power, so I am not sure that is the problem. Especially if another amp worked fine on same power.....

But you have a problem, whatever the cause.

I vote for tech time...... no sense trying to replace tubes if an internal problem has caused the issue...... maybe you damage another tube.

Alex1984 · #14 09-16-2011, 01:14 AM

Tech time. Better to have it fixed up properly.