Finale
Well, they say that no good deed goes unpunished, and I'm a believer.
Yesterday I was taking some voltage readings from the pins of the HAI2002 chip to help a fellow AKer troubleshoot his G-7700. As much as I preach about being careful, I let the probe slip off of pin 5 while glancing at the DMM and drew an arc and a POW. Looks like I bridged between the junction of C31 & R49, over to the track between R43 & R44, which is B+.
The SO relay remained engaged after the arc. I cycled power and everything seemed to come up OK (still on a 135W DBT). Pin 3 on the chip had changed from 4.0mv to 105mv??
I cut power to double check where the arc was and what damage it may have done. The next time I applied power the SO relay would not engage. Both sides of ZD601 read ~40VDC and are slowly discharging with the DMM attached: about one volt every 20 seconds.
I let the voltage at ZD601 discharge until it bottomed out at 14mv. When I tried it again the SO relay still will not engage and ZD601 reads ~40V again. The main caps are quickly discharging down to less than 6vdc and dropping. I don't know where this voltage is coming from.
EchoWars answered some questions about bias, enough to make me realize that I have been chasing wild geese, again. So, I don't have to use my remoted heatsink rig to find the conduction point of the replacement OPTRs. Assuming I can fix the SO problem, I will still use that rig to check out some additional pairs of OP TRs. The tracks on my homemade F-3058 boards cannot take much more soldering, so I want to get them all checked out and select the replacements before one final install to the 3058 bd.
This will be the finale of this thread. Thanks to your support, answers, directions, etc I was able to get this G-6700 operational again, and I have learned Sooooo much. I will start a new thread to try and resolve the SO problem, and eventually try to figure out why the signal through one channel is weaker than the other.
I sincerely hope that others can find some useful information in this thread.
Thanks - - -