Kenwood KA-3060R Idle Current

XgN

Member
2014-08-28 11:03 am
Hello!

Trying to setup Kenwood KA-3060R integrated amplifier idle currents.

Previous owner replaced one channel power transistors (same model) but the amplifier didn't work - noisy audio output with cracks. Saw that the center transistors (those smaller near power transistors) were placed directly to the cooler without a gasket. Double checked the internet, seems there shouldn't be any gaskets. Anyway, isolated them, amplifier sounds good now. It was the collector which was connected directly to cooler.

The problem is the idle current running 300-400 mA (voltage drop accros emitter resistors 250 - 300 mV @ 0,66 Ohm) now. The lowest I can go by adjusting it's 250 mV. The amp is getting pretty hot but still works good under stress-test.

Maybe someone has repaired this amp? Can't find schematics, only part of a service manual where it is stated that idle current should show 13 mV on the resistors. It is an AB class amp, so the idle current is way too high. Anyway, checked all the components around they should influence biasing and they are good. Maybe I could leave the amp like this?
 

XgN

Member
2014-08-28 11:03 am
Seems the one channel that was repaired. All components match the other channel. And this problem is present on both of them. There are only few photos on the internet with a good angle of picture inside. I see there are no gaskets between smaller transistors and radiator. But if so, in my case, both transistors collectors are shorted to ground. Then no idle current is present at all. Would be easy if schematics was.