Samsung PS-42C455 no picture

[PowerAmpFreak]

Re: Samsung PS-42C455 no picture

Datasheet for the RJP30E2 IGBT:
https://cdn.badcaps-static.com/pdfs/...55f488a3d2.pdf

[PowerAmpFreak]

Re: Samsung PS-42C455 no picture

There is an RJP30E2 761082 on the board also, which I assume is the PNP version of this FET, and it measures 0.54v across it's source and drain pins on diode test..

Did you remove both of them and measure out of circuit?
There should be no difference between the two RJP's.
IF you're measuring between collector and emitter (since it's an IGBT) on board, it's natural to have other readings since there are other components in parallell and interfere with your measurements.

[tom66]

Re: Samsung PS-42C455 no picture

There are no P-IGBTs in any plasma display technology that I'm aware of. They cost at least twice as much so the equivalent circuit is implemented with N-type only.

[JonathanAnon]

Re: Samsung PS-42C455 no picture

Did you remove both of them and measure out of circuit?There should be no difference between the two RJP's.

Yeah I took two of them out of circuit and that was a bit of a job. They were not the type with the three pins inline (as in the PDF file above). They were the one with the gate pin forward. I managed to get them out and back in without breaking, but it was tricky. But no combination of any of the boards seems to change the behaviour of the LED on the logic board or hold the Va and Vs up at proper voltage (as both always drop).



I took this picture of the chips BEFORE removing them.. Looks fairly sloppy, I'm wondering did somebody else have a shot at it before?

I'm working my way back through my printouts / manuals etc. I'm gonna start from scratch with it again and give it one more shot.. I'll report back soon.

[tom66]

Re: Samsung PS-42C455 no picture

That forward pin is most likely the drain.

The Vs/Va will shut down on this model without proper sustain operation.

[JonathanAnon]

Re: Samsung PS-42C455 no picture

That forward pin is most likely the drain. The Vs/Va will shut down on this model without proper sustain operation.

By the time I got the chip out of the heatsink, the leads were all pointing in different direction.. :-)

I agree with what you're saying about the Vs/Va. In Yong's book on LCD Repair he suggests putting a bulb across the B+ line as a test load, to help to see if the problem is isolated to the PSU or whether problems are being caused by faults further down the chain. I wonder would putting a 100W bulb across the large voltage be enough to keep it up.... This would at least confirm to me that the PSU rails are not shutting down because of an issue on the PSU itself..

[tom66]

Re: Samsung PS-42C455 no picture

No, it's the control board shutting it down. It'll do this when either Y-main or X-main are faulty on this chassis.

The PSU is most likely fine.

[JonathanAnon]

Re: Samsung PS-42C455 no picture

I've checked every component on the X buffer boards (both left and right) and it seems fine.. I can get the Y Sus and Y-buffer from the UK pretty cheap so I'm gonna get these and work from there..

[JonathanAnon]

Re: Samsung PS-42C455 no picture

Boards arrived today... and


They worked!!.. had a slight issue with a few lines across the screen, but by reseating the cables to the x-buffer board (which I learned last week from Damon Morrow's book) it came right again..

Thanks guys..

[pete_the_geek]

Re: Samsung PS-42C455 no picture

Glad you fixed it! That is a really, really strange issue - I have never heard of that before.

For resetting the EEPROM you can usually go into the service menu and select Factory Reset.

Hi Tom, I know it's an old thread but I just sorted a PS42C450 with exactly the same fault, this thread helped me solve it. 2xRJH30E2 on XSUS short, replaced but still no joy no bang and issue of smoke lol. However proble was traced to s/c cap under silicon on YBUFFER. Never had this before, wondering in other cases if these caps can go short to kill the XSUS and then fry to o/c ?