Ampeg SVT-CL cuts out in every gig

[nickhuge]

This has been an issue for 4 years since i bought it second hand and i just don't know what to do  I tried to get it fixed by John Kelly but he couldn't find what was wrong

Basically, after about 90 minutes in a gig scenario, ie hot venue at decent stage volume, it cuts out. If i turn it back on straight away it won't have any power. if i leave it 20 minutes and turn it back on i might get another 5 minutes out of it.

John put a signal generator on with a high load for a couple of days when I tried to get it fixed last but it didn’t cut out at all. It just seems to be in a gigging environment, hot and sweaty. It does it every time which makes it unusable and unsellable. Is this something anyone has heard of and might know what it could be? I have no experience but im wondering if it's a moisture/heat issue  and if so whether other people have had this problem.

[skidder652003]

is it one of the vietnam models?

 

[nickhuge]

I'm not actually sure this second. I can look when I'm home.

[itu]

So a heat related issue, there is a broken connection or soldering somewhere. How about send/return (use a cable)? May be pretty hard to find: if you have an access to a temp camera like FLIR, it may help to try to find the problematic place.

Is the speaker in top order? Try a different amp and another cab to exclude the problem. And cables, of course.

[stevel]

For a generic overheating problem - is the fan working properly?

More specific things to check - when were the valves last replaced? Have you tried other valves to rule out a bad one?

[tommorichards]

i'd also check the Fan that Stevel mentioned, as i've had a fan cooled amp in the past that cut out once it got warm, and the amp tech that fixed it said it was the fan being clogged. Being on so long and then causing an issue does point to a temperature issue.

[Ricky 4000]

My B-15(T) used to die out... once or twice during a song it would fade to nothing, then come back after a second or two.

No wonder the scumbag who traded it with me was so keen for the deal. 🙁

It probably doesn't help the OP, but our (at the time) studio engineer (bless him) managed to fix it by de-soldering and re-soldering all the connections behind the front panel. It was a guess, as he knew that most faults develop closest to the control knobs and switches.

He was right, because it's not done it again in 20-odd years. 👍

[Phil Starr]

When it switches itself off what is the standby fault led doing? The amp has a feature which switches off the high voltage power if there are any faults with the power output valves. With any valve amp you have to suspect the valves first, they aren't components that last forever and they may need replacing. It's also possible that there are problems with the pin connections, you can pull them out and look for signs of corrosion and maybe try a bit of switch cleaner in the sockets. Don't poke around unless you are confident though and only do so with the amp unplugged and rested for a while, there are some nasty voltages in there.

[Stub Mandrel]

Sounds like a flaky joint.

I fixed a noisy valve amp just by removing each valve then working it in and out of its socket for a while 🙂

At the weekend I fixed a mixing desk that had developed a mains 'buzz' - I just resoldered every suspect-looking joint in the power supply and it magically went away. The main suspect looked like it had been bad from new. Made me look like an electronics god, but to be honest all I had to do was identify where the regulator circuitry was.