Got a 3020 a while back that was in pretty sorry shape but have been slowly making some progress on it. After cleaning it up and rebuilding the power supply (new caps and transistors), finally got sound from the aux (and FM) through the pre-amp outputs but the main amp boards are both bad. I have checked the transistors and replaced all the fuse-resistors and now have 45v on the outputs .. odd both left and right have the same problem. One thing is that the FETS (2SK99) seem to be installed backwards... that is the pin 1 'bump' on the IC is not on the same side as the hash-marked spot on the circuit board that I assume means pin 1 goes to that side. I pulled the FETS and the 45v goes to almost zero. I measured them with the diode tester on the DVM and the G-S = 0.62, G-D=0.62, and D-S=0.03. The other side of the same IC is G-S=0.3, G-D=0.3, D-S=0.03.
Is the FET bad on one side or could it have been installed backwards (didnt look like it had ever been unsoldered but I suppose one never knows)? Is there an acceptable modern replacement for the 2sk99 that is available?
Is the FET bad on one side or could it have been installed backwards (didnt look like it had ever been unsoldered but I suppose one never knows)? Is there an acceptable modern replacement for the 2sk99 that is available?