Samsung LNT3242HX/XAA Power Supply Issue

[kevinm34232]

TV shows red standby LED, will not power on.

After inspection of PS board, noticed high voltage blue cap CM810 leaked all over main filter cap CP803, and one leg was burnt off of the blue cap (B 222K 1KV). Also, nearby RM801 is open, and CP803 tested bad.

Does it sound like the blue cap caused this? I have not found the value of RM801 in the SM I have either, I read somewhere that this is some type of fuse resistor?

[kevinm34232]

Re: Samsung LNT3242HX/XAA Power Supply Issue

Is this correct list?

[vinceroger69]

Re: Samsung LNT3242HX/XAA Power Supply Issue

this may help
http://www.electro-tech-online.com/r...er-supply.html

[selldoor]

Re: Samsung LNT3242HX/XAA Power Supply Issue

Resistor appears to have Red Red silver gold bands, if that is correct then it is 0.22 ohms 5%. Hard to tell but if the casing was pale blue then it could have been fusible.
Parts lists tend not to include the components on the power supply - I dont think you will find the other components listed either. A faulty big cap could have caused this if it went short however you will need to test other nearby parts QM802 and the one next to it.

[kevinm34232]

Re: Samsung LNT3242HX/XAA Power Supply Issue

Im trying to check QM801 and QM802 (FQPF5N50C), I get 0.00ohms reading from G to S on both, .0L on all other combinations, does that mean anything?

[tom66]

Re: Samsung LNT3242HX/XAA Power Supply Issue

Out of circuit? Sounds like gate-source short. If you touched the leads of the transistor, you could have ESD-zapped them.

[kevinm34232]

Re: Samsung LNT3242HX/XAA Power Supply Issue

Sorry this is in circuit right now, what readings should I expect between pins if good and bad?

[tom66]

Re: Samsung LNT3242HX/XAA Power Supply Issue

Gate source should read open or very high resistance.

[multimeter]

Re: Samsung LNT3242HX/XAA Power Supply Issue

FQPF5N50C have a high failiure rate on samsung power supplys.

rm801 is def a 0.22ohm ,and a fusable resistor.

out of curiosity have you checked the main bridge rectifier also?,i wondering if a shorted main filter cap has done this damage.

[senndogg]

Re: Samsung LNT3242HX/XAA Power Supply Issue

i think you should do a list with the failed components. begin with the transistor, resistor, diodes etc. remember when this mosfet fails it takes several components after. in your case (gate-source short) the main IC may have gone.
btw, this psu is 70$ on ebay.

[kevinm34232]

Re: Samsung LNT3242HX/XAA Power Supply Issue

I think G and S are pins 1 and 3, out of circuit is fine, but checking pads where pins 1 and 3 go into show no resistance.

I just ordered the main cap, the resistor and the high voltage cap, we'll see what happens.

[selldoor]

Re: Samsung LNT3242HX/XAA Power Supply Issue

rather than just " see what happens "I think you should wire a lamp across
the fuse - if there is still a short it may save your new parts burning out as it
gives you a little time to switch it all off.

[kevinm34232]

Re: Samsung LNT3242HX/XAA Power Supply Issue

OK, can you elaborate on that? Just hook up wires of a lamp to each side of fuse? By the way initially when I checked voltage I had 120v at bridge rectifier, not sure if that means anything tho.

[selldoor]

Re: Samsung LNT3242HX/XAA Power Supply Issue

OK, can you elaborate on that? Just hook up wires of a lamp to each side of fuse?

Didnt word that very well did I - I have seen it done like that but it should
really be as well as, not instead of the fuse. So you wire a 60 or100watt bulb into the live side of the mains lead. read about it here:
http://www.vintage-radio.com/projects/lamp-limiter.html




[QUOTE
By the way initially when I checked voltage I had 120v at bridge rectifier, not sure if that means anything tho.[/QUOTE]

Is that on the AC contacts? Usually the inner two)- what do you get on the DC contacts. ( Meter on DC - observe the polarity shown on the bridge)

[kevinm34232]

Re: Samsung LNT3242HX/XAA Power Supply Issue

OK I've read about that before.. Are these sold anywhere premade?? It doesn't look hard to make but the time..

[selldoor]

Re: Samsung LNT3242HX/XAA Power Supply Issue

not that i know - heres a wiring across fuse contacts example
https://www.badcaps.net/forum/showth...lamp+bulb+fuse

[kevinm34232]

Re: Samsung LNT3242HX/XAA Power Supply Issue

Replaced those 3 components (main cap CP803, high voltage cap CM810, and resistor RM801). TV Powers up now and is working!

[selldoor]

Re: Samsung LNT3242HX/XAA Power Supply Issue

Missed that last post somehow - well done- another one saved.

[purduejay]

Re: Samsung LNT3242HX/XAA Power Supply Issue

Kevinm34232I'm having the same issue with the CM810. What is the parts numbers of the parts you used to replace CP803, CM810 and RM801?

[Dangermouse1]

Re: Samsung LNT3242HX/XAA Power Supply Issue

Replaced those 3 components (main cap CP803, high voltage cap CM810, and resistor RM801). TV Powers up now and is working!

Hi. Joined just to ask you a question or two. Did that repair keep? Also, did you double check the components you removed to see if they were really dead/damaged?

I ask because I opened up a LN3242HX and found a damaged RM801 (fusible .22 Ohm) with the gunk on it and the nearby caps, just like you reported. Unlike you though, I believe that gunk is the adhesive they add to... to ... well whatever reasons they have for gooping parts together. Reduce vibrations? The same goop was in a number of other places too. Just a little darker and a little crumbly around the RM801 because of heat damage (I think). I could be wrong, but the HV cap seems to be fine from what I can tell (tested in place with ESR meter). Since the gunk could only have come from the HV cap, which seems fine, I think it must be just adhesive.

Obviously there should be some reason the fusible resistor blew... that's why I was hoping you could also report back on if the fix was stable since then.