Insignia 50 plasma, y drive component identify help!!

[topfli8979]

Need help finding a replacement or alternative to a component, part # stth1004fp. 2 leg through hole, attached to its own heat sink. I assume its shorted, did diode test on mmeter, positive to one left negative to other. Is this the proper way to test?

[tom66]

Re: Insignia 50 plasma, y drive component identify help!!

Does it show <100 both ways on diode test?

It's a 400V, 10A diode in TO220.

[topfli8979]

Re: Insignia 50 plasma, y drive component identify help!!

I get a 0.00 both ways on the diode test.

[tom66]

Re: Insignia 50 plasma, y drive component identify help!!

Remove it to confirm. You may also had bad upper Y buffer on a Samsung PDP?

[topfli8979]

Re: Insignia 50 plasma, y drive component identify help!!

You were right, it tested fine out of circuit. Only problem is my buffers and y sustain are built into one board. ANy chance I could find this short?

[tom66]

Re: Insignia 50 plasma, y drive component identify help!!

Do you have a short between Vs and GND?

Does Vs stay up when the Y-sustain is plugged in? (Power it up with it connected -- do NOT plug it in while it is running.)

[topfli8979]

Re: Insignia 50 plasma, y drive component identify help!!

Yes short between vs and ground, tv will not power up with sustain connected. It just cycles from off to on. It powers up fine without the sustain.

[tom66]

Re: Insignia 50 plasma, y drive component identify help!!

Check the fets near the bottom of the board... I think there are four on there. Another user had these short.

[topfli8979]

Re: Insignia 50 plasma, y drive component identify help!!

I replaced 2 of those yesterday, also 2 on the upper heat sink. The ones on lower are still good, but the fets on the upper heat sink shorted upon hooking it up.

[tom66]

Re: Insignia 50 plasma, y drive component identify help!!

I would suspect that either one of those buffer ICs is short or something else is short, but the buffers would be my first suspect. :/

[topfli8979]

Re: Insignia 50 plasma, y drive component identify help!!

I think that buffer IC's are okay, no pin holes or bumps. Did find a IC DVR LOW SIDE/DUAL HI 14-SOIC by upper heat sink that has a short on one pin, would that be because a fet is shorted. Or would that not matter?

[tom66]

Re: Insignia 50 plasma, y drive component identify help!!

If that drives the MOSFETs that shorted, it can sometimes be damaged by the high voltage which appears on the gate pin.

[topfli8979]

Re: Insignia 50 plasma, y drive component identify help!!

It is right in front of the shorted fets, I guess what I am asking is would the ic show short because it is circuit with the shorted fets?

[tom66]

Re: Insignia 50 plasma, y drive component identify help!!

It depends on which pin you are testing. If you are testing the pins going to the gates of the fets, quite possibly.

[topfli8979]

Re: Insignia 50 plasma, y drive component identify help!!

So best bet, replace shorted fet, then test IC?

[tom66]

Re: Insignia 50 plasma, y drive component identify help!!

Remove the fets and test the IC in circuit. What is part # of IC?

[topfli8979]

Re: Insignia 50 plasma, y drive component identify help!!

Irs21856s

[tom66]

Re: Insignia 50 plasma, y drive component identify help!!

Pin 7 is most vulnerable to failure. Check, with fet removed, that it has no shorts to ground or to the Vcc pin (1)

[topfli8979]

Re: Insignia 50 plasma, y drive component identify help!!

Pin 7 seems okay, but pin 2 over to 5 and 6 on opposite side shows short.

[topfli8979]

Re: Insignia 50 plasma, y drive component identify help!!

I assume that is the correct way to test the ic?