06-20-2016, 07:50 PM
Spent some time rebuilding the three electrolytic cans. Six caps all together. Won't bore you with pics. Got them all part and back together again. Reinstalled and started cleaning the under side a bit and found this:
What you are looking at is one of the 42 audio output tube sockets. Look closely and you'll see a black trench between pins 1 and 2. Pin 1 is the heater and 2 is the plate (read pin 1 is at ground potential and pin 2 is at HV with lots of HV AC spikes from the audio signal). What has been going on is that it has been arcing between these two pin and burned the socket. Once the socket has been chard like this the burned area has turned to carbon, Guess what resistor are made of?? The carbon causes more burning of the socket.
Will made a lot of noise because it's arcing/shorting the HV though the output transformer. The transformer doesn't like it so much either. Socket is going to go, luckily I just carried a junk 84 chassis out to the garage which has a good 42 socket.
Terry
What you are looking at is one of the 42 audio output tube sockets. Look closely and you'll see a black trench between pins 1 and 2. Pin 1 is the heater and 2 is the plate (read pin 1 is at ground potential and pin 2 is at HV with lots of HV AC spikes from the audio signal). What has been going on is that it has been arcing between these two pin and burned the socket. Once the socket has been chard like this the burned area has turned to carbon, Guess what resistor are made of?? The carbon causes more burning of the socket.
Will made a lot of noise because it's arcing/shorting the HV though the output transformer. The transformer doesn't like it so much either. Socket is going to go, luckily I just carried a junk 84 chassis out to the garage which has a good 42 socket.
Terry
