1994 Sanyo TV, turns on, no picture, turns right back off.

[MRX37]

Well, I replaced the bad resistor, put it all back together and... nothing! same problem.

I went through all the trouble of getting the needed parts for nothing!

[radiotvnut]

I think I'd check the voltage at the collector terminal (center pin) of the HOT. Just set your meter to measure at least 200 volts DC and clip the negative lead to one of the chassis heatsinks. Attach the positive lead to the HOT collector and hit the power button. You should have around 130 volts DC. Since the set is dead, you'll likely either read very low or zero volts or a high reading of around 170 volts. If the voltage is low or zero, you'll have to trace the B+ line back to the STR30130 to find the problem.

[MRX37]

I did that, and got a whopping... 2 volts.

So I assume something's bad between the center pin of the HOT and the regulator IC?

[radiotvnut]

Take out the HOT and recheck the voltage. If it jumps up, the flyback is probably bad and loading down the voltage.

[MRX37]

Seeing as there isn't much between the center pin of the HOT and the flyback, can I just assume the flyback is bad? This TV's quickly turning into more trouble then it's worth.

I guess I could take the HOT out and test again, but where would i clip the positive lead to?

[radiotvnut]

Trace the foil back and connect it to the flyback terminal that goes to the HOT.

[MRX37]

Okay, I removed the HOT, and connected my positive lead to the flyback pin, which was easy enough to find. Turned the TV on, and still only read about 2 volts.

WTF...

[radiotvnut]

OK, I'll dig out the schematic again. The problem has to be somewhere in the power supply.

[radiotvnut]

I just had another thought while I re-locate the schematic. Locate the main filter cap in the power supply. That's the huge cap with a value between 330 uf and 680 uf at 180 to 200 volts. Connect your voltmeter to the positive terminal of that cap and the negative lead to ground and see what you get. Should be around 165-170 volts.

[MRX37]

It's a 470uf@ 200 volt cap. Okay I'll do that.

[MRX37]

Okay, doing that got me a reading of about 150 volts. This is with no HOT in the TV

Now what?

[radiotvnut]

That voltage sounds fine. I think you can reinstall the HOT at this time. Now, check the voltages on the STR30130.

Pin 1 is connected to ground (0 volts).
Pin 2 should have approx 136 volts
Pin 3 should have approx 155 volts. This is the raw B+ input from the big filter cap.
Pin 4 should have 130 volts. This is your output pin.
Pin 5 is not connected to anything in circuit and should read 0 volts.

[MRX37]

So I know ahead of time, what if I get either too low or too high voltage readings?

[radiotvnut]

I think it would be better to measure the voltages and we'll go from there.

[MRX37]

All right. I'll get to it later tonight. If this yeilds no answer, I might very well junk the set. Tomorrow's trash night and I'll probably find another one anyway.