Weird.... Thoughts?

[Jbeaudin]

I have a RV100 MK1. Today I took it to practice and it worked fine for about 15 minutes and then no sound through either channel. If I strummed my guitar every so often I would hear a fizzling sound (only in the clean channel, dirty channel had absolutely nothing coming through) and it would get quieter and die out (this would happen in about 1 second). Prior to this happening I did have some power board issues where I'd lose power and it would make the amp pop (happened about 6 times). Once I got home I checked the internal fuses which all checked out good, and swapped out the phase inverter tube just for fun. Plugged back in and same thing. Then about 3 minutes in the amp started working properly like nothing ever happened.

Does anyone know what might have caused this situation to happen and what can be done so it doesn't happen again?
Thanks.

[bclaire]

Weird. My first thought is a tube-related issue. I'd try replacing tubes or bring it in to an amp tech to be really sure...

[Jbeaudin]

I just put new preamp tubes in it last week.

[Les Paul Lover]

I just put new preamp tubes in it last week.

Did the problem appear before or after that swap?

New valves are prone to early failure, the reason why most sellers have a 90 days warranty.

My next question is why did you change the preamp valves?
Preamp valves typically last 4 to 5 times as long as power valves. My thought being that I'd the problem was already there and you swapped the preamp valves hoping to sort it out, you may have replaced the wrong valves.

Power valves require the amp to be biased though, so you would need to bring your amp to a tech if that's the issue.

[Jbeaudin]

So the reason I swapped preamp tubes was because I noticed a difference in tone, especially in the dirty channel. It lacks that thick low end tone that the amp had so I figured I'd swap the preamp tubes to get my tone back. The preamp tubes did help the tone slightly, but my thick bottom end didn't return.

If it was a power valve failure, why would I lose all of my sound all together? That amp is designed to run 2 out of the 4 if you have a failure.

I'm pretty hesitant to play it live right now as it could quit again. I'm going to play through it and see if I can get the amp to reproduce the problem.

[Les Paul Lover]

Yours is a MKI like mine?

If so, yes you should be able to running at half power, but the way that works, the fuse corresponding to that pair of power valves would be blown.

How did you check your fuses? With a multimeter or just visually ? The only fuse I've had blow on me looked just fine, it was only the multimeter that told me it was actually blown.

If your fuses are 100% good, my bet will be on a dodgy preamp valve. They are most likely to fail early on, or last for a very long time with just gradual wear.

If you haven't replaced your power valves yet, and have played your amp quite a bit, it'd be worth looking into replacing them too, that may well get you your low end back.

If that fails...... Techniques Time.

Now that you said it was working again, did you get your low end back with it?
Have you tried the amp again?

[Jbeaudin]

Yes it is a MK1 like yours, just orange instead of black.

How would I know if the tube is no good? I did use a multimeter to check the fuses but I probley had it on the wrong setting. What's the correct setting to use when checking a fuse?

My power tubes were probably changed less then 100hrs ago. This was several wars ago, but I haven't played it very much since then. Thinking about running KT66's next time though to see how I like the sound.

[Les Paul Lover]

To check fuses, simply put your multimeter to a low ohm setting. Apply each probes to each side of the fuse. If your reading is near zero, it's fine. If the fuse is blown, it won't be conductive anymore, and your reading should be the same as for.. Carpet, wood... . Anything non conductive.

As for preamp valve, the only test you can do is to replace them, one at a time, for a valve that you know works.

Doing it one at a time enables you to fibs the dodgy one.
Unfortunately, you should get the amp biased when changing power valves.

[Jbeaudin]

For sure on the biasing, I always get a tech to do it when swapping power valves.

I'll try it again with the mutilmeter and see if anything shows up.

The problem is that the amp is currently working again, so I'm not sure it's a fuse issue. Are there any chips in this amp? When I played it last night the amp stopped for about a second or two and then came back fully again. Might have to trade it is for a two rock. Lol.

[Jbeaudin]

Amp started cutting in and out a little bit the other night again. I also found the problem more prevalent when the volume is turned past 4 or 5. Another thread I was reading had similar issues and it turned out the power tubes were done. So I'm going to check out those. Maybe even swap them out just to be sure.

My question this time is: Can one bad power tube make the entire amp go quiet?

Thanks.

[Les Paul Lover]

Yes, it can.

The bummer is that unless you have a valve tester or access to one it's difficult to pin point which.

[Jbeaudin]

Well I've wanted to do a KT66 swap anyway... so this might be the opportunity to do it.

[pedecamp]

I'd clean all your tube sockets with Deoxit. You do this by spraying the tube pins and then inserting and reinserting the tube into the socket several times to clean them. While youre doing this clean all your inputs the same way with a cable and also spray some into each of your knob pots and twist the knobs back and forth several times. Let it dry and see what happens the next time you play. If it keeps happening replace your tubes one at a time to isolate which is the bad tube. I suspect its tube related.

[Jbeaudin]

I'm starting to think it could be tube related as well, or it would still be unfunctional...

I tapped on all the tubes with a wooden skewer and I found the FX loop tube and phase inverter tube (but mostly the FX Loop tube, and the inverter tube is brand new) made a tinging - higher pitch noise when tapping on it, but only when the amp was on, it wouldn't reproduce it in standby or off mode. It did not, however make any hissing noise like what I've read microphonic tubes will do. Could this tube be on its way out, and would it be possible for a tube to cut all signal but come on again at some point?

I also read that if a person has an FX Loop that never gets used - just like my situation, that it can get dirty/gum up and cause the amp to go silent.

Does the cleaner need to be of a lubricant type as well? I've damaged pots before using standard electrical contact cleaner.

[pedecamp]

Get a can of Deoxit its electronic spray this is what the pros use and recommend. Clean everything, my 2204 was working fine and after cleaning everything my tone changed noticeably for the better, in your case it might fix something that's not connecting well.

Get a couple preamp tubes to replace those noisy ones, its cheap enough to do.