Mark 3 mysterious fault

[MarlonBoogie]

Hi there, i'm new to boogieboard and look forward to getting involved but my first post concerns my amp which is in intensive care. I have been using my boogie mk3 blue stripe faultlessly since acquiring it in the 90's. At a recent gig however it just stopped functioning. It would light up and fan would work but closer inspection showed that only a tiny output volume was present. If using it at normal volumes it sounds similar to the sound coming from a large pair of headphones. Turning up input and master volumes made this easier to hear. All the functions seem to operate as they should and volume changes with channel change as it should, just less than 1% of volume present. I have checked and replaced all the valves, an electrician friend has checked the heating resisters and main transformers and the capacitors are all in pristine appearance. I can't imagine what the problem might be. Are there any boogie users out there who have had similar problems resolved and could share their wisdom with me? Many thanks. Marlon

 

[stokes]

It could be any number of things,bad tube being the best case scenario and most likely suspect.You say you "checked and replaced all valves" if you did indeed do that then we can rule out a bad tube.You say "an electrician friend has checked the heating resisters and main transformers and the capacitors are all in pristine appearance". A bad component wont always look bad so appearance isnt really a "check".About the only thing I can tell you to check,short of opening the amp and doing a signal trace to see where in the amp you are losing signal would be to "bridge" the effects loop.You can do this by simply plugging a guitar cord or patch cord into the in and out jacks of the effects loop.The signal is passed thru the loop when no effect is used via a shorting jack.It is quite common for this contact to get dirty or for the shorting tab to fail to make good connection.If,when you bridge the loop as I described,the volume comes back,you found the problem.Somrtimes cleaning the contacts is enough to cure it,but in some cases the jack or jacks has to be replaced.