50" plasma smps questions

[CalebG]

So I dont think they are open circuit, they seem to pass the voltage on to the secondary side. Im not sure what the waveforms are supposed to look like as I just got the scope up and working. What is the best wave form to input on the primary for testing and what should the output look like generally? I made a sine oscillator to test it, does it work better with a square or sawtooth? Seems my order got sent ups and wont make it here till next monday.

Monday
Well I got my replacement capacitor, put it back together with a replacement fuse (blew as soon as I plugged it into the wall). I tried the 100 watt light bulb technique in place of the fuse, the bulb glows brightly the whole time I get kind of a squashed sine with flattened top and bottom on the output of the bulb, getting similar waveforms through most of the primary. However Im not sure if the 100 watt bulb is able to source enough juice as it is a 400watt tv. I may give it a try with a 500 watt halogen bulb instead. Does anyone have a generic switch mode schematic that shows all the expected waveforms at each major component?

 

[CalebG]

found it!

Ended up being the str x6769 ic after I removed it the light bulb goes on for a second then goes out. on the bottom of the chip is a big crack and burn mark, probably went when the little blue cap blew. Off to find a replacement on the net
**broken link removed**

 

[CalebG]

Well I received my new chip in the mail yesterday and soldered it into my board. Applied the light bulb which turned on for about 3 seconds then shut off. Applied a new fuse with out failure. Then I switched on the tv at which point my new ic exploded after about 5 seconds and blew the fuse again. This board is really trying my patience, any ideas?

 

[CalebG]

I hooked up the scope to where pins 1 (drain) and 2 (source) go into the board, I was expecting Just dc voltage but am getting about +150v on 2 and pin 1 is reading -150v, but it is pulsed dc. Is this normal, I cant seem to find any other shorts on my board?
**broken link removed**

 

[Jimlee]

Caleb , did you get any further with this? I have the exact same issue and upon finding a replacement pcb online I zoomed in on the pic to see the cap had blown apart on that one too. If you found anything I would really appreciate hearing about it.
Jim