Well, fired it up today. Brought it up on the variac, slowly. All voltages came up and it looked pretty good. Nothing on the speakers though.
The heaters were not heating in the 4 output tubes. Were they all bad? Took me a minute to remember that the output tube heaters are in series, and one of them was likely bad. Put in all new tubes and voila!! audio came out the other end.
Spent about an hour figuring out and adjusting proper bias, had to look up these weird tubes. Seems they were originally made for Horizontal deflection in TV's. They can take up to 7Kv on the plates. Wow! Plate dissipation was not that high at 10w, but hey, I set it for about 75-80% bias. Then to listen.
Besides the usual exercising of the bad switches, something was really wrong. Sounded weird and the bass control did weird things when adjusted. Eventually realized that I had made a mistake when replacing the caps in the bass control circuitry. I had been short the 0.003uf caps and had to wait a week to get them and then another week to get the time to do it, and had put them in wrong.
OK, now we were cooking. Played first from my Ipod. Bela fleck and Tariketh. On my bench speakers. Justin was in the shop and after he left, I hooked it up to the big speakers and cranked it up. It seemed quite clean, but there was something I didn't like about it. Kept fooling with it, and finally put the output on the scope.
Well, I was running it into total clipping. It was so clean, it just seemed I could turn it up lots more. Turned it down to where it's running just below clipping. Very clean with powerful bass.
That got me curious so I measured the output just before clipping and did the math. Hmmm, puts out 38-39 wpc or so. Impressive. I was expecting 20-25 wpc.
So, it's been cranked for a couple hours. OPT's get a little warm, but that's all. Power transformer the same, just a little warm. Wow, cool amp. And I don't just mean temperature wise. When I read about the tubes I was skeptical. Can't nothing that was made to drive a TV screen sound very good. But I am happily wrong about that.
I'll have to listen for longer to really form an opinion, but... with this little time listening, I would rate my CA303/BA303 combination a little better and seemingly a little more power, but damn close. Sansui knows, or knew, how to make tube gear.
I'm gonna try bypassing the tone section and see how it sounds. It's a very simple very rudimentary circuit and it might sound better with it out.
Nothing from either one of the tuner sections. I'm not surprised, some of those tubes don't even get warm. I definitely wanna get that stuff working, but not a priority right now.
The picture is from testing it on my workbench. Variac on the left.