Summary

Typical cheap Zenith bedroom set from the late 80s.

Literature

• Service Manual

Notes

• If set won't power on and you hear a squealing/hissing noise it's the SMPS with no load. Check the two electrolytic caps near the SMPS IC (right next to the flyback in the back center of the board) - C3432 and C3434. Test them out of circuit and make sure they pass ESR, else replace them.
• If set is totally dead and fuse is blown, likely the SMPS IC3431 is dead. Pull from circuit and check for any pins which have low ohms. If resistance check passes, check pins 2,3,4 as the B,C,E of an NPN transistor in diode check mode. If it fails then you can replace it with an STR53041. Try to find one with a "dot" marking after the number, this indicates a closer spec to the original Zenith part. If SMPS IC isn't dead, check for shorted HOT or bad flyback. If Flyback and HOT are fine then you'll have to do an in-depth board diagnostic.