I have finished my VTA 70 install on my old 1960 or 61 ST70. I have spent a couple of hours researching the board. I think I have problem solved, but i thought I would ask for some help.
Bias is way too high. With pots turned all the way down, bias is leveling off at .70. I thoroughly cleaned and tightened all the sockets. And still have the problem.
Here are some pertinent values:
red/blk wire bias connection 55vac
Other end of diode -45vdc
each location of pin 6 at board -22.3 to -23
Across pin 2 and 7 of each output tube 7vac
rec tube across pin 2 and 8 5.5 vac
rec tube pin 4 and 6 379vac
So have I got a bad diode (or did I toast it soldering it in place)? Or should I look somewhere else? Can I replace that diode with a 1N4007 or do I need to go the electronics store?
Thanks in advance for any and all help.
Bias is way too high. With pots turned all the way down, bias is leveling off at .70. I thoroughly cleaned and tightened all the sockets. And still have the problem.
Here are some pertinent values:
red/blk wire bias connection 55vac
Other end of diode -45vdc
each location of pin 6 at board -22.3 to -23
Across pin 2 and 7 of each output tube 7vac
rec tube across pin 2 and 8 5.5 vac
rec tube pin 4 and 6 379vac
So have I got a bad diode (or did I toast it soldering it in place)? Or should I look somewhere else? Can I replace that diode with a 1N4007 or do I need to go the electronics store?
Thanks in advance for any and all help.