K8060 bias

Kits Audio Hi Fi Projects
1

Hello,

Well I’m back to the K8060 which I shelved for a whille in frustration. I’ve replaced all the semiconductors and still have a problem with the bias being too low. . The amp generally works but its not loud enough and distorts.

Can anyone give me a few pointers as the the voltages in various parts bias circuit when the bias is set properly (i.e. in the bias set up part with no input) ? This might give me a clue as to which component is dead/not working correctly. i’d like to compare values in the resistor chains etc. i assume the Vbe of the TIPs must be a little above 0.7 volts at least.

Also the bias pot is a 1K7. Would this cause a problem since its specified as 500ohm on the circuit diagram?

The bias voltage across R19 is maximum 1.5mV. I changed out the IN4148s as well.

Please help!!!

Thanks

Jules

2

Actually the normal “quiescent” voltage at the collector of T6 (without input) would be the best to compare mine to I think!!!

Cheers

Jules

3

I have measured the voltage across R13 which is the 3k3 resistor and it has 0.5V at the bottom (also the collector of T6) but it has 32 volts at the top (junction of R12 and R13) and its hot!! Any one know what could cause this? Something is dragging this point to 0.5V which doesn’t seem right to me! T6 seems ok though, I’ve tested it.

I can’t honestly afford to keep changing the whole set of transistors…

Cheers

Jules