Thanks all for the help. I am learning a lot here... two steps forward, one step back.
Here's where I'm at with my SA-200:
Originally b ought from ebay as 'for parts or not working'. Mainly just needed deoxit. Both channels worked, but both had a dc offset of 80 and a big 'thump' through the speakers when I turned the receiveroff, which i thought might be attributable to the dc offset.
Following Ecluser's advice at the beginning of this thread, i became fixated on trying to reduce the dc offset. I began to test by adding resistors in parallel to the 614 and 613 resistors. Long story short, one of my probes wandered and I ended up shorting out the left channel power IC, IC601.
Good news: I was able to get one on eBay that seems to work ok. I replaced the IC and that channel worked again.
I couldn't get the old resistors out, but i found it easy to solder new ones in in parallel. With a 680 ohm resistor in parallel on 614 and (I think) an 1100 ohm in parallel on 613, I got the dc offset down to .005 on the right channel and .015 on the left.
And now it doesn't seem to thump when i turn it off (though I have limited data points).
So here's what's up now:
The right channel, the one that was fine, works fine when I first turn the unit on (cold). But after a few minutes, it deteriorates, getting more and more staticky until you can barely make out the music on that channel. I checked the related IC, and all appears to be fine.
The only thing I've noted is that there is a big boxy cement-ish resistor labeled 5W 180 ohm J 2836 that gets very, very warm during operation (I included a picture). I checked resistance when the unit is off and it's still 180 ohms. I did not measure when warm. I also realize I didn't write down the resistor number from the board. I need to trace it on the schematic but I wouldn't think that is related to an issue in just one channel.
Also, another thing I found very odd - the unit seems to continue to play for about 8 seconds after I turn off the unit. I had my iphone playing through aux on headphones, and after I switched off the receiver, it kept playing. Even more odd, I wanted to check the dc offset when the unit was off - so I plugged in my probes to the speaker jacks after the receiver was turned off - and the iphone picked up volume and started playing through the headphones on the Technics' headphone jack for second!
If anyone can offer help with the deteriorating right channel issue, I would be very grateful. Also, if the staying on for 8 seconds is a concern, please let me know.