Thanks Dwight for some insights into rectification. Always fun to learn more. And thank you Dave for the 7218 test wiring. That is what i did minus the caps for bench testing
As I wait for the 7812 in strong hopes it fixes the dead board, maybe I can pick your collective brains on the nonlinearity board:
Shouldn't somebody who can actually understand the magical schematics be able to kindly find a small set of parts that creates the voltage slope that makes the crt beam go from left to right. And whatever determines the speed / slope of this voltage increase needs to be replaced. And as we can exclude the caps, what is it that changes horizontal coordinate on the beam, if it is not a cap?
The beam is scanned from the center to the right by the current in the yoke rising at a near linear rate after the horizontal output transistor (HOT) switches on. Normally there is a yoke coupling capacitor and a series linearity coil which slightly alter this profile, but these two components are generally fairly reliable. The yoke coupling capacitor, called the "S" correction capacitor is generally a special high quality part with a very low ESR and non-polar. Essentially the rate of rise of current is V/L Amps per second where V is the power supply voltage and L the yoke's inductance. So obviously the power supply voltage must be stable, it normally is. It relies also on the HOT being in a saturated switching state, meaning its base-emitter current is high and its collector to emitter voltage stays at a low value during the time it is switched on.
Generally the width control coil is a plain variable inductor and the Linearity coil has a fixed magnet, there was a case a while back where the linearity coil's magnet had fallen off the assembly.
When the beam has been deflected to the right side of the CRT face, the HOT is switched off by its drive pulses that originate from the H drive signal. Then the magnetic field in the yoke begins to rapidly collapse, in a sinusoidal fashion as you now have an undamped tuned circuit with stored magnetic energy. This produces a high voltage positive flyback pulse on the collector terminal of the HOT. This is transformed up even higher by the overwind coil on the LOPT (Line output transformer) to acquire the EHT for the CRT. After 1/2 a cycle,it also reverses the yoke's magnetic field, so the beam has now flown back to the left side of the CRT face.
In any case, you only get to see 1/2 a cycle of that sine wave as the flyback pulse, the reason is that when the collector voltage of the HOT attempts to swing more negative than its emitter, the Damper diode (better called Energy recovery diode) is forced into conduction, in this case part D704 on your schematic. At this point the beam is on the left and the magnetic field energy in the yoke and LOPT returns in a leanear manner to the power supply, this scans the left hand side of the screen. When there are severe H scan linearity defects on the left side of the scanning raster, it always pays to test and or replace the damper diode.
The usual protocol to repair a set like this would be to use a x 100 scope probe (or x 10 if that is all you had, ok in this case but not a color set) and look at the voltage on the HOT's collector, it should be uniformly low throughout the scan indicating that both the HOT and the Damper are conducting properly. If they were not then investigate why. If the were then turn attention to the yoke coupling cap and linearity coil assembly.
Any additional resistance in series with the yoke tends to degrade the linearity, compressing the right side of the raster, be it, the HOT not switched on hard, bad connections/soldering or a higher than normal yoke coupling capacitor ESR. Normally though if it was the HOT not switched on properly, it would also be heating significantly.