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I was able to get a copy of the Sam's Photofact schematic from our city library, but there was an error in scanning; whoever scanned it included Set 668 instead of Set 688 on the first four pages! I went ahead and ordered one from Sams itself, but it had the same problem; sent them an email and they got right back to me with a corrected schematic by the next business day!
I took out the chassis to inspect the existing caps for replacemtn, and cleaned the tube sockets and pins with electronics cleaner and tightened the pin sockets. I also replaced the HV Rectifier, Video Amp, and AGC tubes with NOS ones (GE for the HV Rect and AGC, Raytheon for the Vid Amp) I got from eBay for a few bucks.
Put it back together and there's a big improvement in the AGC (almost never buzzes anymore), the picture is sharper (more focused) and the blooming is almost gone.
Many of the caps look to have been replaced, but I still need to replace 7 old plastic-tube capacitors, so I'll have to order them. There's still a little pincushion distortion, slight blooming, and other minor issues but I'm optimistic they the cap replacements will cure these issues; can't hurt at least.
When I redo the caps I'll take it apart all the way to clean out some dirt on the inside of the plastic screen protector, and clean the tuner which is a little scratchy (though I always have in on CH4, I sometimes need to jiggle it a little to lock back onto the input from the digital adapter), and also clean the controls; volume and vertical hold are a little scratchy as are the height and linearity adjustments on the back.
The TV's working quite well at this point already though - the kids an I enjoy watching old TV shows on it like Bewitched, I Dream of Jeannie, the Dick Van Dyke show, and the Twilight Zone.
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