peavey encore circa 1984

[novernmunkee]

hi there can anyone offer any help or advice on this? story goes like this...
i have a peavey encore 65 all tube amp. it uses 2 6l6 output tubes 3 12ax7's and one 12at7. the last 4 i'm not 2 sure about what they do?
anyway amp was working then with out warning went dead. opened it up to find 1 of the fuses had gone. fuse in question was rated at 1a 250v glass 313 american standard?
got some new fuses same amp and voltage rating. popped it in blew immediatley. powered it down pulled both output tubes and engaged main power. light indicated power on and fuse didn't blow. then put 1 power tube in powered up as before, but output tube wasn't getting hot or glowing.
i then very stupidly flicked stand by switch and boom smoke started.
i've tracked the burn't components down to 4 capacitors and the surrounding resistors. with these capacitors being near the output tube pins and being considerably bigger than all the others am i right in thinking these are the filter caps? what i carn't understand is why fuse didn't blow as before and how much damage have i done?
this is my first tube amp and i am trying to learn and understand it but unfortunatley my knowledge has run out. any help or advice greatly appreciated. many thanks neil

[Mars Amp Repair]

hello neil,
without looking at a schemo, I'd say you had a shorted power tube as well as filter caps that were leaky anyway..

the power tubes are the largest current drawers in the circuit & when you pull the them, the B+ voltages rise up substantially & sometimes even exceed the nominal ratings of the filter caps.

Normally with good caps this is not an issue as they are designed to take some peak voltages for a short period of time, but with older & possibly leaky caps, the extra voltage on them & hence the extra current probably took them to their graves. the resistors that feed the caps then burned up.

You could measure the caps with an ohm meter to determine if this is the case. Then you would need to replace the filter caps & of course the burned resistors. It would be a good idea to try a bulb limiter if you don't have a variac to bring the unit up.

glen

[CharlieP]

With an amp of this age you most likely should do a Cap job. The power tubes will make the fuse blow every time on this too. At the very least you need new power tubes. As stated above resistors could be burned. It is of no use to keep changing the fuse until you at least put new or known good tubes in it and go from there.

[Gtr_tech]

I just missed out on one of those. Was on Craigslist.....60$....oh well. Coulda been a fun project.

[Enzo]

And don;t be confused by soot. If a resistor went up in flames and smoke, it might coat all the nearby caps with black soot, but they could still be fine once wiped clean.

Sounds like you lost a power tube, and it burnt up some other parts, like screen resistors.

[novernmunkee]

peavey encore

thanks for the replies so far. i'm pretty sure the caps mentioned have gone and the resistors round it arn't reading on my meter unlike the others in the circuit. i've put up the scematic but i might have to bite the bullet and take it to someone who know's what there doing. neil