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On my marshall amp with 4 el-34's the sound faded from normal volume the it turned to a very low volume for a sec or couple at times. From what I have read this could be a problem with the power tubes. I looked into my amp to find that one power tube doesn't seem as bright as the others, so this could be the failing one.

If I need to replace my tubes, what would you guys recommend for weezer and Paul Gilbert tones. I don't really mine for tubes to run clean, I'm mostly into using distortion.

Before getting carried away with replacing new tubes you should do some investigation work first. Imagine spending a fortune on new tubes then finding out that your old ones were fine, you'd be pissed!

Although, it does sound like power tube failure. If you're fairly confident with opening your amp up then you should try this. Usually you'll be able to tell immediately if something more serious is wrong; there'll be a bad smell or something will look 'burnt out'.

I'd reccomend this first, at least before you start to throw money at it anyway.

Try cleaning all the speaker FX loop and input jacks. This has happened to me a couple times and it was the humidity of summer dirtying up all the jacks. Might be that simple.

How do I clean the jacks?


Originally Posted by kevlar3000Try cleaning all the speaker FX loop and input jacks. This has happened to me a couple times and it was the humidity of summer dirtying up all the jacks. Might be that simple.

1, happens to many amps, but mostly Marshall's.

You spray some electronics cleaner in the jacks and then work a plug in and out a few times.

You can get some cleaner at Radio Shack, but I am partial to DeOxit from Caig.

If you are unaware of how long your power tubes have been in the amp, change them too. They will need to be biased.

Thanks for the advice guys. I just tried plugging/unplugging all my inputs cables and the amp seems fine now.

Get the electronic contact cleaner spray can of stuff from Radio Shack or wherever. Unplug the amp, spray it in your jack, run your plug in and out.

Make sure you ask whether the contact cleaner is safe with plastics. I did have the amps on one of my amps disintigrate with the stuff.

Okay I tried spraying all contacts and the same problem happened last night when I was playing. When the problem occured I just rotated the speaker cable in the jacks and I think the problem went away. So I'm not sure if it could the speaker cable. I've been using pedals every time that problem occurred. Do you guys know if there is a way for me to find the problem now? I think I might buy another speaker cable to try, I probably need a backup one anyways if I use two cabs in the future. What speaker cables do you guys recommend I try thats not like monster cable expensive?

I just got a new planet waves cable from Guitar Center last weekend. The sound decreasing suddenly just happened again. I guess I'll try using the contact cleaner on all the jacks again. If that doesn't work I'll probably get a amp tech to check it out. Should I try tapping all the tubes with a stick to check for problems? What sounds should listen for to tell if a tube is bad?

Try playing for a while without any pedals at all. It could be one of them causing it to happen. I had this same experience before and one of my pedals was having fits. Pulled it out of the chain and the problem went away.

I like neutrik speaker cables. I just pm'ed you John Nau's #.

Actually I could come out there sometime and take a look too.

I just got my amp back a two days ago from the amp tech. and the sound problems are gone now. He said some of components were oxidized and some spots just need resoldering. Everything is fine now with the amp, except I had one problem with the first time I used it since I got it back. Once I let it warmup on standby for like 5-10mins, I turned on standby and no sound came out. I checked all the plugs were in. After about 2 mins sound started to come out and it worked fine after that. Do you guys know anything that would cause this problem? Oh and the same power tube is not even lit up at all now. He said he checked that tube and it was all right. I think he said something about the filament in the tube is why it's not lighting up, but it still works. Is this thing normally happen with tubes? One more thing I noticed was that I needed to turn the volume above 2 to get the same volume I used before that was less than 2, but thats probably cause some pots got changed or cleaned up.

Well, at least the source of the original problem is taken care of. Glad to know it was that simple. As for the power-up no sound, it may be that the caps were fully discharged when you got it back so on first power-up it took a little longer than what you're used to to fully power-up. Just my guess.

You either have a bad tube or that tube's not getting power. Swap two outside tubes and see if that one glows on the opposite side or not. This could be the source of the volume having to be turned up a little higher than before.

It's one of tubes in the inside, so should I switch them.

Yup. Swap the two inside tubes. See if the no-glow follows the tube or if the same socket gives no glow.


Originally Posted by ErikHTry playing for a while without any pedals at all. It could be one of them causing it to happen. I had this same experience before and one of my pedals was having fits. Pulled it out of the chain and the problem went away.This happens to my marshall (AVT50). When I have my footswitch plugged in.. my clean channel doesn't drop volume.. it will have a sudden burst of volume, and its not switching from clean to OD it must louder!

Clean the jacks??? Footswitch is dying?

Thanks

I would clean the jacks if that doesn't work you could take it too a tech.


Originally Posted by ErikHYup. Swap the two inside tubes. See if the no-glow follows the tube or if the same socket gives no glow.

Okay I switched the tubes around and the tube is glowing now, but the volume drop happened again. Do you think it could be bad solder spots in my cab or some wiring thing in there?


Originally Posted by greendy123Okay I switched the tubes around and the tube is glowing now, but the volume drop happened again. Do you think it could be bad solder spots in my cab or some wiring thing in there?

So all 4 tubes are glowing? Are all 4 glowing even after the volume drop? It could be that the pot itself is just going bad if all 4 tubes are glowing as they should.

Yeah all tubes are glowing as normally.