Testing Power Supply in TV

[peterk]

Teac CTV CT-M6845 doesn't start, no B+, no smaller voltages. I have put a lamp on the B+ rail before the LOPT. I have tested each component individually in the Primary cct. There is no SMPS, just 3 trans., 3 diodes in series, a few res., and some ceramic caps. There are no electrolytic caps in it either. ACvolts are present.

Protection is via feedback from the Secondary output to an OptoCoupler whose o/p then connects to one of the smaller trans. (across B-C pnp).

Anyone have suggestions on how I can test the PS please. Can I override the optocoupler. Obviously, I assume, that the Primary cct has to start oscillating somehow but this I can't figure out.

[tv.service]

First check if you have about 300v on the drain of the switching FET transistor.

[Guest]

Yes there is, btw, it is a trans (collector), passive measurements test each component ok, dc volts drop are across all silicon devices, pulses do not start.

[tv.service]

You must check if you have 300v at the collector. Also check if you have the right voltage at the base of the transistor and check if you have the start-up voltage somewhere in the circuit. This voltage is usually 12 or 18v.