Unit came in with intermittently blanking out picture audio still on.
Almost looks like scan loss trip and no error codes tripped as well.

Background: this is most complicated ATC221 design, have many shut
down circuit interconnected. Scan loss trip is bunch of low signal
transistors with number of transistors monitoring the H & V scan
signals that hooks into all CRT ICs and another set of circuits also
monitors the voltage outputs for the convergence power supply output
for proper startup & cut off if not within specs this cut the off/on
switch to power supply. This is diffcult one to troubleshoot but I
DID. WHEW!

Checked the shutdown circuits, H & V scans, main power supply & some
voltages, all GOOD. Till I plugged in heat gun on same outlet and set
video cuts out on surge of power at instant of heatgun plugging in
with audio playing. Mmm? Variac comes out and adjusted AC slightly
higher, set stablizes. More interesting!

Slowly narrowed down to convergence power supply but where? Looked at
optisolator and found what is not right. Solid -24V and drops slightly
if I turn AC down bit never around -18V as schematic specifies. And
unit get more unstable on lower AC. And find the convergence supply
stopped running.

On a clue, yanked the DC power to the convergence plug while unit is
playing, video cuts out with audio still playing. Now that's the
*hint*.

OK! pull convergence board for 5th time, Went over the power supply
fine tooth comb style and BINGO found RP44 slightly higher. Perfect
8K ohms instead of 5.6K ohms. This connects to the optisolator to the
TP24.

That bugger now FIXED!

RCA stuff is having number of resistors issues still but what a bugger
to search for. :/

I had ITC222 with x-ray resistor divider values going high and cause
false positives. That two is 1/8W tiny through hole resistor under
the vertical heatsink. Precision value 1% type btw. It was helped
when I found a tip on RCA online.

Cheers, Wizard