Since the last look, I checked the tubes and powered up the 1800. Non-power tubes all tested good; mixed bag of brands throughout. One of the 12AX7's was labeled "Baldwin;" apparently an organ amp tube. The 7591's all checked good, but one of the older Fisher labels was significantly weaker on emission (my B&K 707 won't test mutual conductance for this type) compared to the others. I then powered it up fairly slowly with the variac and noticed nothing untoward.
Lamps all work and had sound from both channels (as expected from the seller's description), the FM tuner was working well and quite sensitive even with just a clip lead antenna in the basement workshop. AM tuner worked as well, but considerable hash at certain points in the band--could well have been the antenna being mounted directly to the power transformer (as above) or noisy lighting fixtures. We'll figure that out. Everything sounded quite good, even into my bench speakers--no hum at all and very little tube rush in with the volume up full in the phono position.
The Stereo Beacon lamp came on whenever the selector switch was in "FM Stereo Filter" position, but does not light in "FM Automatic" even with a strong, known stereo signal is tuned to max signal strength. Will have to look into that. There is a tube that controls activation of the beacon lamp that tested good. Any thoughts on what to look for?
The FM signal quality doesn't fall off symmetrically away from maximum meter deflection. Noise happens quicker on one side than the other, so that, combined with the Beacon light issue, may indicate at least an alignment of the FM IF is called for.
I decided I didn't like the work around the replaced capacitors; too many 'flying leads' and soldering not what I'd like in places, axial caps wire-tied to a 3 watt power resistor, etc. I want to leakage check the remaining multi-section can (C91A-D) with my Sprague TO-5 before I decide to stay with it, but it was quite cool during 20 minutes or so of power on. The other two have been replaced already.
The B+ rectifiers appear to be replacements, R-170 B's, which are spec'ed at 1000 PIV and 2.5 amps, so they should be good. Work around the replacement couplers and small electrolytics looks good all around, so no worries there. The resistors in the bias/filament supply have not been changed despite the replacement silicon bridge and presumably higher voltage, so I want to check the bias voltages and 7591 cathode currents. One of the 7591 cathode resistors tests at 11 ohms. I'll probably replace them all with precision units.
After I do the clean up work, I'll test voltages and power test the amplifier so see if I need to make any 7591 changes. I have a matched quad of Tung Sol 7591A's standing by if I need them.
So, a little work to do before I bring it up to the listening room!
Dave