On Sat, Apr 29, 2017 at 7:36 PM, Aaron Jackson via cctalk <cctalk@classiccmp.org> wrote: >> Since it doesn't smoke, I'm thinking the horizontal sweep >> transistor may have gone out. It may have shorted, which >> then may have burned up the primary winding in the flyback >> (if left on long enough). I'd check that transistor for a >> short, and then you can trace a few traces to identify the >> primary terminals on the flyback and see if they are an open >> circuit. > > Hmm, not good news. zero ohm between pin one and three of the transistor > you mentioned. To be fair the board around it looks a little brown, but
Is this with the transistor soldered to the board or removed? If the latter then the transistor is shorted base-emitter. If the former then you are measuring the resistance of L200 and the secondary of T201 (horizontal drive transformer) in seroes which will be essentially zero. > I assumed this was just because it would have got hot. Could replacing > this cause damage to the flyback? I seem to have a low resistance on > what I think is the primary coil. Most flyback windings have a very low DC resistance. In any case the most common failure is a short between a couple of turns of such a winding which will ruin the AC performance of the transformer but have almost no effect on the resistance. That's why you need to test such a transformer with a ringing tester, not an ohmmeter. -tony