The following tips are based on my article,published in "TELEVISION", Vol.42No2.Dec.91 issue:
Some models such as the G9-12,G15,G30 and NV280 have a similar power supply.In the event of Q1101's failure,replace D1120 as well.Ensure that Q1101 is fitted with a smear of heatsink compound and the plastic part( VG00922) which meshes Q1101's heatsink to the isolated metal shield body-the heatsink is at mains potential as the chopper transister's collector (pin3) is connected to the metal tab.The grey-coloured plastic is between the heatsink and body.If the power supply works intermittantly take a closer look at the sub-assembly (VJB 01211) where D1117,D1104 and R1105 can become leaky or open.On the secondary side,the axial electrolytics tend to lose capacitance,which can manifest as obscure symptoms.
From the foregoing discussion,one would come to the conclusion that only semiconductors fail in these units.Those of you who are long in the tooth and short in hair would grimace and point out that practically anything can go wrong! Electrolytics in these power supplies work hard and work near hot components,which result in dried electrolytes.Use 105 degree C types and shun 85 degree C electrolytics here.Always substitute a capacitor to prove its innocence.No result symptom can issue from the pulse coupling capacitor at the chopper pin 2.Use a high voltage (350 V) component here.Failure to accept a cassette or shutting down shortly after or while playing can be also due to low capacitance after the bridge rectifiers (82 microfarad/400 V). I have pulled my hair out because of a recalcitrant fault: Poor colour in playback,which was eventually cured by replacing an electrolytic in one of the secondaries of the chopper transformer. If you mend Sony TVs for a living,you already know the feeling-Hell is nothing compared to repairing electronic products.This is not to suggest that the aforementioned products are below par,but only that their repair can be very involved.
