Sony KV 1212

[DaveWM]

it was pretty easy once I gave up guessing and got the scope. You could clearly see the issue present on all 3 cathodes of the CRT. tracing back to the collectors of the drive transistors and it was there as well, but the bases looked perfect. I figured it had to be in the power supply to the collectors.

What got me was I thought they were supplied by the mains B+ (per the schematic) but as I trace the pcb the orange supply wire I saw it going somewhere else. then I see a diode where a choke was supposed to be (the pcb even had both symbols choke and diode printed on top), and the only thing else was a wire to the flyback to a pin that was not ref in the schematic.

hmmm, that was when I realized it had a boost supply and of course the 1st thing to check was the filter cap. I had check the other caps in the LV flyback supply but missed this one completely since I did not know it existed.

oh and this is a bit odd the BOOST for the screen comes from the horz out transistor, while the voltage supply I refer to comes from the flyback, Whats odd is the fly does not power the yoke there is a another transistor and transformer that does that. So not even sure what to call this supply from the fly that is used for the video out, its only about 15v higher that the mains B+, maybe I should be calling it flyback B+ 3 while the flyback LV supply is B+ 2 and the mains would be B+1 its a bit confusing. buddy of mine is getting me the correct schematic, that should help.