fender pro/concert reverb amp

[amptech]

Hi all,


Question, has anyone worked on the fender pro/concert valve amp this model came out rougly in 2002.

the problem with this one is after replacement of o/p valve's gt6l6's two of and rebiasing the unit plus a soak test of two hour's the main fuse blow's!.

Has anyone had the same fault with this and who could shead same light on this matter.

cheers.

[Enzo]

Fender amps are pretty much all the same inside, only the details differ.

If it takes a couple hours to blow, chances are good it is drawing too much current just sitting there, so the fuse is almost ready to pop all the time. Otherwise it is an occasional event, such as an intermittent short within a power tube that seems to usually take that long to decide to occur.

I assume the mains fuse is the proper T2A. Remove that fuse and connect your ammeter in its place. Or if you have one, plug the amp into a current-metered mains outlet. Now you can monitor how much current the thing draws just sitting there. I don't usually work with 240v mains, but I'd guess a proper functioning amp at idle would draw maybe 1/2 amp or less. In any case, if it is drawing something close to the 2A fuse rating, then we have to isolate which part is the problem. One way is to leave it in standby. That removes the B+, so if there is still excess current, then we look for trouble on the heater line or other low voltage supply. If the current is too high only when B+ is on, then we look for trouble on the high voltage. Does the choke get hot? I*'d pull teh power tubes and see if the vurrent drops a lot or a little.

If the current stays fairly low, then we must look for some intermittent event, and the first place to look is to the power tubes. Try a different pair in it. And you can try some tests on the new tubes too, tap on them fairly sharply with something. Any pops or crackles?

[amptech]

fender pro/concert reverb amp

Hi all,


Just like to say cheers to Enzo for pointing out some sound advice in regards to the fender pro/concert reverb amp problem.

After much huntting about i did get the right circuit diagram in the end for it and this helped track down all the correct voltage reading's within this unit.
and so after a 5hr long soak test all was well and the only thing to do was fit back together job done.