1990 zenith no HV

[rca2000]

You are correct---this is a cold chassis. The SMPS powers most stuff. Not sure if they only "boost" the 200 volt line with the flyback or if it is totally fly derived. This chassis was introduced in 1987. It lasted a few years before replaced with something likely cheaper to produce.


It sounds as if the 'screaming noise" was a runaway SMPS---I have seen this many times on this chassis and many others in all things. I do wonder if you have HV. If the G voltage is at the CRT--you DO have HV. Maybe that resistor for the Filamant line got damaged or such, during repair. Maybe even something has come off on the CRT board to the fil. line. One way to PROVE this--connect a small bulb, such as a # 47, to the fil line on the CRT board. If it lights decent--the fil line is ok. If not at all--you have no fil voltage. If there is no G voltage, likely no HV or fil voltage either--as those come totally from the fly.


At this age--look for a number of bad caps in the vertical and flyback areas. I recall a LOT of cap problems in the vertical ckt. on these sets, would cause retrace lines and/or linearity problems.


I used to work on these chassis qiute a lot. not a bad set, totally cold and fairly built (for the time period). Have one or two, and a 13" model for sure. KInda like them, and Flybacks did NOT fail often. Sometimes would lose H drive, from a bad driver transformer or a resistor feeding it , IIRC. a 1990 set SHOULD have a decent tube if not ran to death, that was right before the "switchover" to the Goldstar tubes. I now the 19" sets GS tubes did not die as often as the 25 and 27 inch sets--but they DID go bad some.