Fender M-80 Combo amp Mods or revisions on power supply or circuit?

[Slobrain]

Hello Fellow ampagers,

I wanted to see if anyone has a revision on the 1989 Fender M-80 combo 80 watt amp? Reason Im asking is that the low voltage side in my amp looks like its cooking the 5 watt 330 ohm resistors on the plus and minus and its probably due to fender designing cost effective... I'm wanting to see if I can replace the 330 ohm with a 350 ohm and get away with it as I dont have any 330 ohm 5 watters and probably cannot find them locally.

Also has anyone done any mods to this amp to make it sound better?

Thanks

Slobrain

[Ronsonic]

Your sub is a whole 6% off, that'll be fine. Almost within tolerance. Give them some height above the board while you're at it.

The resistors aren't necessarily the problem, that design will eventually cook the board. Especially the parchment colored single-sided boards you usually see in the amps that have it.

I've converted such amps to use a standard 7915 / 7815 combination to replace that part of the supply and get the heat off that board. The regulators run much cooler anyway.

Don't have anything specific for mods, what would you like to change about it?

[Slobrain]

Hey Ronsonic,

Well, I got this amp at a pawn shop pretty cheap and it had both input jacks broken. When opening the amp I seen the sand resistors had cooked and a bit of the circuit board too. I just want to get it running and then see if anyone had any good mods for this design for tighter bass and smooth distortion. These old M-80s seem to be pretty good for SS. I'm more a tube amp guy but I do like the SS for practice and maybe a small jam session too. Regarding the regulation for the low voltage I agree it would have been better for Fender to have done that but they chose the less cost effective route.
Heck, I'm out a practice on amp repair. I sort of laid off for a long while and trying to get back into it again. seems the brain loses more knowledge these days as I aproach the big 50...

Cheers