strat1080

Hi all. New member here. I heard there are some Valveking experts on this board. I have an issue with this amp that just happened today. I bought this amp used about a year ago and have been using it with the proper footswitch.

The amp was working perfectly but out of the blue, all of a sudden there is very little volume on the clean channel and it won't switch over to the gain channel unless I hit the gain boost button on the amp. This is very strange. With the channel button pushed in I hit the channel selector on the pedal and the red light comes on but it doesn't do anything.

I basically have to crank the volume up to at least 12 o clock on the clean channel just for it to be audible when it used to be pretty loud before. The gain channel with the gain boost pushed works normally though. Plenty of gain and volume. I can't access the regular gain channel though. I can only get distortion if I push in the gain boost button.

Any ideas?

Thanks,

Chris

GeetarHeero

Welcome to UG

There are a lot of amp gurus around who could probably help you diagnose it better than myself. However, have you checked all the tubes? That's always a good place to start.

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strat1080

I've checked just to make sure they all light up, which they do.

monwobobbo

it may be the tube for the clean channel just becuse it lights updoesn't mean it's necessarily good. you may have a problem with the internal channel switching in which case teh signal isn't really being let through. try a different tube (or just swap the ones for each channel and see what happens) if that isn't the issue then talk to a tech.

strat1080

It looks like it could be a tube. I swapped them around and now I don't get any sound out of any channel regardless of if the boost is engaged. I'll try swapping in some new tubes. Maybe that might fix the issue. I'll cross my fingers.

strat1080

I went ahead and put in some new preamp tubes and the problem remains. Any other ideas?

ihartfood

power tubes.

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R45VT

That doesn't explain the channel switching concerns. Would explain volume.

TS- does it switch channels properly? (Has that concern been fixed?)

Just an FYI we have had a few people on here that have found bad solder joints. If you give your amp a good thump is there any change?

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strat1080

What I find strange is that if I engage the gain boost I have normal volume that I would expect from this amp. I can't access the normal lead channel. Only with the gain stage. The clean channel seems slightly distorted and isn't as loud as normal. The switching still isn't working.

R45VT

Yeah... time to open it up. Keep in mind there are lethal voltages present in the amps. Do not touch ANYTHING in there until you are sure the capacitors are drained.

If you feel comfortable opening it up and inspecting we can often help. If you can't see anything visually then time to take it to a tech.

In this thread there are pictures of a bad solder joint.

http://www.ultimate-guitar.com/foru...oo+for+us+cheap

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strat1080

Well. I got around to taking the chassis out today and looked around. I really didn't see any red flags with any of the components. I sprayed some contact cleaner on all of the push buttons and all jacks. I gave the amp a fairly good thumping (not excessive of course) and I still have the same problems.

After swapping tubes around a bit I can get some pretty good volume out of the clean channel but it distorts a tad which I dont' remember it doing before.

After really toying around with it here is what I came up with. If the channel select switch is in and I try to change from clean to lead channel on the footswitch there is a brief muting of the amp but it goes right back to the clean channel. The red light will illuminate on the footswitch but the volume control of the clean channel still operates the amp. If I hit the gain boost button then it will access that portion of the amp and stay there even if I push it back out. The only way to back to clean is to change the channel with the footswitch.

Would power tubes cause anything like this?

What do you guys think?

I bought this amp used at a pretty good price so I'm kind of hesitant to spend big bucks to have a tech fix it for me.

R45VT

It's not a tube from what you are describing with the channel switching concerns.

No bad solder joints?

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strat1080

The whole PCB looked pretty clean. I looked at it for a while this afternoon and really couldn't see anything wrong.

R45VT

Do you have a foot switch to change the channels?

Does it responsible differently with that?

Sometimes the jacks don't make good contact and don't work from the front of the amp due to it thinking the foot switch is hooked electrically.

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strat1080

It seems to respond the same. There is an audible pause when hitting the switch to change channels with either the button on the amp or the footswitch bit it seems to go back to the clean channel. There is a loud hum and some crackling. I'm wondering if one of the tubes is shot so maybe the amp isn't getting a signal to change the channel.