Kustom 72' coupe

[fiddlemandwayne]

My amp just fried and i believe it was the two bias resistors R102 &R101 I cannot find out what the value and wattage is of these two resistors becouse they were chared. These amps get real hot becouse of the tubes so I put two computer fans on it to keep it cool ,but I forgot to turn it on this time.Has anyone else had a problem similar to this ? It would get so hot ,you could not keep your hands on it for more than 3-4 seconds.
Thanks!
Dwayne

[tartanphantom]

Sorry to hear about this. The Kustom Coupes are awesome sounding amps, but they are prone to high temp issues because of the biasing scheme.

I haven't had a burnout, but my Coupe used to get so hot that the trem/vibe circuit would stop working. Like you, I installed a small multi-speed twin computer fan on the power tube cage. Once I did this, no more problems! I think these amps should come with a cooling fan as standard equipment.

Sorry I can't help you on the schematic, but if you email Kustom, I understand that they will send you a pdf schematic, but they will also caution you that it will void your warranty. So if yours is still under warranty (mine is not) you'd be better off sending it to an authorized service tech.

[gtrdon]

I replace those two resistors with 100 ohm 10 watt ceramic resistors,Also don't forget the two 47uf 100 volt electrolytic caps.One more thing to check are the 4.7k input grid resistor that go to pin #5 on the out put tubes.a quick and dirty test is to locate pin 5 and check for -25 vdc on all power tube sockets if so chances are the grid resistors are fine.The 100 ohm resistors help to lower the heat.thecorrect resistors are 82 ohm 10 watt.

[Jonnferrell]

Just in case anyone is looking at this old thread, I've owned too many of the coupes--four of the 72s and I think four 36's and one hardtop. The 72's are the problem child, but they sound the best. The fans are an absolute necessity if you're going to use the amp, and I suggest wiring them to the pilot light instead of using an extra transformer to plug it in the wall. I used to use an old phone charger, but one gig I forgot to plug it in and about halfway through the night I kept smelling that electrical component frying smell that one hates. I made it through the gig, but I hardwired the fans in after that. I also took some plywood and made a new back panel with two to let the heat out. That has kept my 72 running nice and cool--well, just warm, ever since. I do love these amps.