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So another update to this one, June 17th.
Got the shading issue ironed out, turned out to be a bad new capacitor that was across the contrast control so that got replaced again and now all is well there. Other issue I'm still dealing with is horizontal sync bending that would normally be attributed to borderline AGC overload, AGC is set on the conservative side and there's a fixed bend to the right about 1/4 way down the raster from the top. Can't see it on the scope and it's there regardless of the source be it straight from a TBC or consumer grade DTV converter on CH-3 or 4.
Still fighting a vertical issue and this might be from well baked caps near the vert tube, resistors have all been replaced and a subsequent check shows them on the mark, Boost B+ is +1160 volts and supply is at +413V so those are good.
Did inject some raw composite video into the 1st video amp after lifting the 3rd IF amp tube out and got excellent results. When I replaced the IF strip I added a two lug terminal strip near the 1st video amp tube with the wire connecting directly to test point 2 so I could do the IF alignments with all the covers & shields in place, this is the junction of L14 and pin-2 of the 6LM8 video amp on the T933 schematic. I'm working with a T940 which is very similar however it uses a 6MU8 for the 1st video and calls for what looks like over 2V P-P signal on that grid. So the plan is to address the few remaining issues then add a tube based composite video amplifier to feed the test lug via DPDT relay which will also open the B+ line to the IF amp effectively isolating it, this way the DC integrity of the grid is maintained and the signal will be behind the 4.5 trap.
More to follow shortly.
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