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Worked on a lot of these back in the day. Memory is used external variable supply to run horiz osc 19V.It should start at around 5-6 volts.( It was important to run external supply through a diode to prevent damage to supply when sets scan derived 19 V source came up). You could then bring the set up on a variac while monitoring the collector of the SD613 with a scope and the 130 V B+. I remember there is at least one electrolytic coupling cap between the oscillator IC and the H driver that would change value and distort the drive and cause repeat SG613 failures. Other issues were bad solder dips , good practice to re-solder all SG613 collector circuit components. Never had a bad flyback or tripler in any of those. Those 114 degree sets had fantastic pictures if CRT was strong really outshined all the competition at that time. Actually enjoyed working on them because you had something really nice once repaired and set up.
73-
Paul
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