My lead III will run for about 3 minutes then turn off. I'm not sure what's wrong, but wanted to try to repair it myself. Does anyone have any suggestions or a schematic.
stevem Messages: 4742 Registered: June 2004 Location: NY
Senior Member
These amps like many other model Kustoms are built with thermal circuit breakers that on the schematics are called thermostats.
These are designed to open up the AC wall voltage going to your amp if the running temperature of the output stage exceeds 182 degrees F.
This is the likely cause of your amp shutting down after only 3 minutes of bring played, or even just being on in some caes.
Can you read a schematic, post back a reply and I will explain to you how to proceed.
This is a easy fix, so don't sweat it!
stevem Messages: 4742 Registered: June 2004 Location: NY
Senior Member
The thermal breaker is a bolted down black button with two white with a black stripe wires on it.
It's mount in the middle of the heat sink that the output Transistors are on.
If you turn the amp on and blow on it with a hair dryer I bet the amp will shut right down!
If that's the case you can just jump it out for now and use the amp , just first check that the amp is indeed not running hot which would indicate a bias problem.
didn't have a hair dryer so just bypassed it and amp ran fine, when i went to turn it off it was too hot to touch though. Scared it might be a bias problem. Dang that seemed to work.
pleat Messages: 1452 Registered: June 2004 Location: Belding, Mi
Senior Member
I had a K150-7 combo amp and it did the same thing, run for a few minutes and shut down. Turned out in my amp the diode had slipped out of the clip on the heat sink. Snapped it back in place and never had any problems after that.
pleat
stevem Messages: 4742 Registered: June 2004 Location: NY
Senior Member
Good point Pleat!
Yes, if that two lead diode in that clip next to the thermal breaker in out of its clip , or not held tight in its clip then the amp can run hot and shut down.
Be careful when moving that diode, as it's leads are fragile, and also make sure that it's leads are not touching the clip.
If your thermal breaker is ok and the bias diode is held in the clip well then the amp should be able to sit on and just idle for hours with the rear of the chassis only feeling warm to the touch, not hot!
I adjusted the diode and the amp is running cool. Thank you all for your help. This is the first forum I have ever joined and needed help. It was more than I could have hoped for. A working amp with just 20 minutes of my time. Wow! Thank you again, John