F-50 Problem - Sound goes in and out....

[Alniner]

Picked up a used F-50. Love the amp.

However, after bringing it home I noticed that the sound seems to come and go from time to time. Sometimes right when I turn it on sometimes after I've been playing for hours. So I can't pin-point the timing.

It's not that the sound goes away completely, it's like I'm losing some gain and tone, then it comes back. I purchased new tubes(jj's) to replace the stock mesa's as I though it was a tube problem. That didn't help.

I'm thinking of taking it to a local mesa dealer. Any ideas what i should do next?

 

[jbird]

When this happens, do you try to compensate the volume loss by turning that channels master up? Have you checked the linaerity of the volume pots? Is the effects loop engeged? Does it happen on both channels? Eliminate any processors or bad cables?

 

[Alniner]

It's not just the volume that is affected. It's the overall sound, gain, tone...etc. It is the amp as a whole that is affect, not just the clean or dirty channels. However, most noticeably the dirty as I play with that the most.

I've done the cable test, it's not them It's not the tubes So I'm running out of ideas. Not sure what "linearity of the volume pots" means. Sorry, if you could elaborate for me, I'd appreciate it.

It doesn't seem to make a difference if I use the effects loop or not. I happens when I just plug in with nothing else, or when I add my effects chain. Same problem.

 

[jbird]

When it happens, have you tried moving any of the the controls (one at a time) to see if anything happens? A bad Treble or Volume pot could be at fault here! If not, you've already done some good diagnosing, time to take it a step further, a tech!

 

[Surfcaster]

+1 on checking the controls...not just turning them, see if there's any play when you push/pull them. There should be just a tad, but not a lot. I had a similar problem that was due to a pot coming loose. Easy to fix, just bend the tabs holding it together back down, but you have to pull the chassis out.

If that doesn't pan out, call the Techs at Mesa...they are really good at troubleshooting over the phone.

 

[Alniner]

I'll try those suggestions tonight and let you know. Thanks for the ideas!!

 

[fdesalvo]

hopefully the muting fets for the channel switchin are ok.

 

[Alniner]

OK. Tried a few things last night.

The biggest problem is that I can't make the problem appear. However, after playing for a couple minutes last night it was back(or gone really!!)

I tried playing with each knob. Turning each one in turn in both directions as well tried wiggling each one. Nothing made a difference, except for what each knob was suppose to do.

I'm starting to have a bad feeling that I'm gonna have to send it in to a dealer to get checked out. Should I call the Mesa folk first to see if there is something they can do or just bring it in to my local guy? If I have to bring it in, any ideas what this might run me to get checked out?

 

[Surfcaster]

I would definitely call Mesa...the most you can lose is the cost of the long distance call, and it might save you having the amp serviced. If you have to have it serviced, I have no idea what it will cost...depends on the servicer.

 

[marlon]

Hey - my 4 x 10 LSS does the exact same thing whever it feels like it. The sound and intensity sort of wanders around as if a hand was turning the master volume knob very slowly down and back up again. Whenever I wait for it to happen it never does.

 

[Alniner]

Marlon,

I still have not found a fix to this problem. these days, when it happens I just keep playing. lol. Have you had any luck with solving your amp issue?