|Posted: Sun Aug 06, 2006 1:20 pm Post subject: KV27S15 power up problem - Q591, Q601, Q602, R607
|I have a Sony KV27S15 TV that went out - we were watching it and it just went out. I replaced the HOT (Q591), the two power switching transistors Q601 and Q602 and R607. All were bad. Measured the VDRs and they looked good ...at least as a static check.
After I put the new parts in (Q591, Q602, Q601, R607), I used a variac and slowly brought the AC up. The power relay kicked in (~40-60V AC) and I eventually got it up to 110 with only sound. I had it on for 40+ minutes with only sound while I was looking for why I didn't have video. I pushed on the heat sink for the power transistors and suddenly, the video came on. It was on for ~1-2 minutes and I heard this chirping and then the set went dead (Q601, Q602, Q591, R607 all got shorted out again...actually the resistor R607 opened up). Q591 CE is shorted and so is it on Q601 and Q602.
Any ideas on what might be the cause? I have another set of parts but I'm hesitant to put them in without knowing what else is wrong. Could it be the flyback or the horizontal drive transformer? How can I test the flyback or HDT?
Also, anyone have a service manual for the KV27S15? I've got the power section of the schematics and that's it.
Any help would be appreciated.