Tube Doctors: Your Diagnosis, Please

[Phantasm]

My guitarist has an Orange 2x12 Combo amp that sounds fantastic. Over the past year however, sometimes when he turns the amp from Standby to On he's unable to get guitar signal through the amp; he just gets a strange crackling/popcorn sound. If he switches back and forth a few times the problem usually goes away.

The other night, the problem wasn't going away. We tried everything and eventually changing outlets solved the problem, though we're not 100% sure that was the cause.

Based on these symptoms (mainly the crackling noise with no instrument throughput) what say the tube masters among you about the possible problem with the amp?

I'd tell him to bring it to a tech but I couldn't name a good tech in this city if I wanted to.

[Decker]

He probably has a loose or degraded connection somewhere. The popcorn sound, to me, indicates that there is filament power and B+, but no signal. If it was mine, the first thing I would do (after unplugging it) would be to take the tubes out and use a spray cleaner on the tube sockets and potentiometers and switches and the 1/4" jacks. I use Caig, but there are others. If you have a multimeter, you can check to see if the power and standby switches are working properly by testing the resistance in the off and on positions (did I mention that you should unplug this first?) Then clean the tub pins with steel wool or very fine sandpaper. If you use steel wool, make sure you clean off any fine particles that could cause a short. You can GENTLY tighten the tube sockets with a very small tool. I use a dental pick, but a screwdriver for eyeglasses would work. They can loosen up over time from heating and cooling. Clean the plug on the power cord, again with sandpaper or steel wool or a steel brush. I'm guessing that changing outlets worked because you moved the amp and the connection jiggled and reconnected. After this, it gets a little more complicated, because you are going to have to loose for a bad solder joint. This requires reheating and reflowing the solder joints with a soldering iron. You could try replacing the rectifier tube. Take your time, and remember that tube amps have lethal voltages in them. The oldtimers (I may be one of them by now) used to tell newbies to work with one hand in their pocket to avoid voltages through the chest cavity. Still good advice. Good luck.

[BassmanPaul]

Take the amp to a tech - they have then in new Orleans. His bill will be much much less than your life is worth!

Paul

[Phantasm]

Thanks guys for the advice.

Techs are harder to come by here than you think... I had to have a pickup swapped so I asked around and went to a shop that was highly recommend. He wired the blend pot backwards and now the knobs for the EQ are loose. That's kind of how things roll here when it comes to techs!

[T-Bird]

Hi.

Even if the techs are few and far between, Paul's suggestion:

Originally Posted by BassmanPaul

Take the amp to a tech - they have then in new Orleans. His bill will be much much less than your life is worth!

Paul

is still the safest one.

The problem can be as easy as a faulty switch, but changing even that will expose the DIYer to lethal voltages.
Kinda worse yet, a hefty zap through one's fingers can mean NO MORE PLAYING. EVER.

Amp repair isn't rocket science, but it's one of those things best to be left for those who can perform the repairs safely.

Regards
Sam