Hi,
I have a K8020 preamp.
When I am plugging the device, immediately the relay RY9 is activated and the input 1 (AUX) is selected.
There is no reaction when I am pressing the other switches; the LED of the input 1 is always on.
The mute is not working.
I checked all the voltages and everything is OK.
I removed and checked the T9 and T10, they are OK.
I checked all the transistors, resistors, capacitors, diodes etc., they are OK
I bought a new VK8020 chip and I replaced it without any improvement.
Could you please advice?
Michalis
Please note that the VK8020 is a programmed microcontroller. If you bought an empty microcontroller, it will not work. Check the assembly carefully for solder bridges around the ยต-controller. Check that controller receives +5VDC.