1986 Fisher television

[Alex KL-1]

Some testing to try...
1 - measure the photocoupler diode voltage (pin 1 to pin 2, IC001). If is less than 1V, the primary switching is soft, no longer providing sufficient power, and secondary comparator A003 no catch it and not makes the diode to conduct. Suspects: the A002 module or capacitors near it, including the C011 and all small ones (since some couple pulses and high ESR on then upsets the regulator).
2 - if measures 1V or a little higher in the photocoupler (indicating conduction of internal diode), the A001 module was in error in it's internal reference. For testing this, a dangerous proposal: sub this module for a series string of 110V zeners (or a 110V zener) only for testing, removing the A001 module (and changes the photocoupler connections for proper conducting, I can draw it if you wants to test it), to check if restores near 110V regulation. Is not recommended to run continously the zener string due to temperature voltage drift.