F 50 bizzare problem

[jonnyrats]

Hi all
Hope you can pop me in the rite direction . Got a used f50 a bit back . Loved it . Did 1 gig mint . When we got back into rehersals after about an hour a bizzare thing happens. My amp started cutting out . But only when someone else was playing theirs ? Singer sang thru pa . My amp died . Other guitarist / bass player played . Mine cut out. Then after another 10 or 15 mins mine was quiet as hell and noisey if that makes sense? Tried other tubes and was same after an hour . Bit the bullet and ordered the correct full set of tubes from Watford valves here in the UK. Took the amp to work and metered out the caps and resistors . All seemed fine . Re flowed the main solder joints . I'm a maintenance electrician so got a rough idea bit not electronic trained . Fit new tubes . Played quiet at home for half an hour fine . Went band practice and clean chanel was fine but drive channel had a vicious feedback howl . Used clean channel and after an hour same original problem again . Amp felt quite hot at the back . I know this is somewhat normal but ? . Love the amp but after paying 550 second hand and 200 on new tubes I'm at a loss. Anyone else experienced this before ? Is there a common problem I should be looking at ? Or anyone know any good mesa amp repairs in England? I'm in North West. Cheers in advance for any help . Amp had original mesa tubes in by the way when I got it . Thanks . John

 

[Alan Harper]

I have the exact same fault on the drive channel too. Excruciating feedback howl when ever you touch the gain and bass control. I have only just replaced a few of the controls that were damaged and yet to follow up on the howl. Id be interested in others experience on this amp too. I suspect a cap problem but yet to investigate further.

 

[Alan Harper]

Hi John, I'd be interested in any response you get for this problem. I too have very bad feedback howl on the drive channel ad the owner said the amp kept cutting out too... I suspect a cap problem somewhere but the Service Manual I have is almost useless... so much missing detail in the diagrams.

This entry was added after I decided to join up the forum - hence the delayed extra text.