Samsung 23" LCD P2350 Inverter Repair

[whistlergonewild]

Re: Samsung 23" LCD P2350 Inverter Repair

Ok. So I finally got my caps in the mail. The first picture are the ones I bought on ebay from hong kong. The others I bought at a Japanese electronic store on Main St. in downtown Vancouver.

I have replaced the caps and so far so good, but I've only had my monitor on now for 8 minutes....see what happens....keeping my fingers crossed.

[whistlergonewild]

Re: Samsung 23" LCD P2350 Inverter Repair

Well I had it on for 10 minutes and then it switched off...the control buttons on the bottom stay illuminated, and then after a few minutes they turn off then back on with the display. So still the same results....on for ten minutes then off for minute, no difference even with the new caps.

Any ideas what to try next.

[retiredcaps]

Re: Samsung 23" LCD P2350 Inverter Repair

Post a picture of the top of the Rubycon cap and the bottom of the cap. The top should have a "K" style bent, if not, they are fake. If the bottom has a "bulleyes" bung, it is fake.

[bomcla]

Re: Samsung 23" LCD P2350 Inverter Repair

controls the output transformer of lamps. probably is not working properly!

[fishstix]

Re: Samsung 23" LCD P2350 Inverter Repair

Any further luck with this? My monitor is exactly the same and starting to exhibit the same problems with turning off. Quick google and its common fault.

Seems to be heat/time related as it happens after being on for a few hours. I'm happy to strip it down and replace the caps but before doing that would be nice to hear some positive results.

[whistlergonewild]

Re: Samsung 23" LCD P2350 Inverter Repair

Hey fishstix. The only time I had positive results is when I had a 12V fan blowing on the heat sink. So I don't know if replacing the component the heat sink attaches to would solve anything but putting a fan to it did. Also Im not sure the part number or how to order that piece, but I did google the issue I'm having and I read somewhere that this is the culprit of all mayhem, then again I also understand how it could be the caps, but since I have replaced the caps twice with no success Im thinking it's the other component.
I think I'm going to hook the fan back to the 12v and use the monitor only as a backup.

Hey....anyone interested in buying a monitor that works some of the time? $60 and it's yours.

[fishstix]

Re: Samsung 23" LCD P2350 Inverter Repair

It seems to be a real common problem. Quite a pain as its a nice monitor when it works.

I've just resoldered the caps (getting that back lid off is a pain) but still experiencing same thing.

I'll buy some replacement caps and give it a go. Might see if I can track down a replacement to the combo FET/PWM controller that you're cooling. Since that's having an effect its either working too hard due to something else broken, or is actually the broken piece.

[whistlergonewild]

Re: Samsung 23" LCD P2350 Inverter Repair

hey fishstix, If you end up finding a replacement piece please update this thread and tell me how it goes.

[fishstix]

Re: Samsung 23" LCD P2350 Inverter Repair

Well I've replaced the two little FETs that drive the transformer. Managed to find the replacement IC parts (the two little 8pin SOIC). (This is what was at the start of the thread but I managed to find the actual parts)..

And! Just the same. Resoldering the caps previously didn't help so think I'll either for for replacing the caps and/or replacing the fet/pwm with the heatsink...

Now I need to open up the monitor again to get that part number..

[whistlergonewild]

Re: Samsung 23" LCD P2350 Inverter Repair

If you replace the fet/pwm on the heatsink please let me know the outcome. I posted the cap sizes and some high-resolution photos on this thread that you may be able to find the part numbers from without having to open the monitor again. I have opened my monitor so many times now that I have it down to a fine art.

[CroTech]

Re: Samsung 23" LCD P2350 Inverter Repair

Nice repair, just bought the same monitor. At first it had 2 seconds to black, then I measured the secondaries on the inverter (1400271 C 09TM13-C) and they were like 1.1kOhm and 96kOhms so I changedt it with TMS 92903CT which had secondaries 1.6kOHms.
Turned it on, and it was working for a few seconds and since then I cant turn it on at all.

I suspected the schotky diode so I tested it and all pins were shorted, desoldered it and tested again, turned out good and not faulty.

I wonder could I have the same problem with the mosfets and how to check them?

And if I have the same problem could anyone write it on the picture in the first post which mosfets are IRF540N and which IRF9540N? Thanks in advance.

[CroTech]

Re: Samsung 23" LCD P2350 Inverter Repair

Also the whole board was recaped with Samxon capacitors

[momaka]

Re: Samsung 23" LCD P2350 Inverter Repair

I wonder could I have the same problem with the mosfets and how to check them?

Get the data sheet of the MOSFETs and check for short circuit between Source and Drain, Gate and Drain, and Source and Gate for each MOSFET. In particular, any short circuit between Gate and any other pin makes the MOSFET highly suspicious. In such case, remove MOSFET and test out of the board.

[CroTech]

Re: Samsung 23" LCD P2350 Inverter Repair

The problem is mosfets are so small i cant read what is written on them... I will try taking a picture of it then zooming in. I read that u need a bias current so u can check a mosfet?

[Rtech]

Re: Samsung 23" LCD P2350 Inverter Repair

This might help.

http://www.4qdtec.com/mostest.html

[CroTech]

Re: Samsung 23" LCD P2350 Inverter Repair

mosfets had gates shorted, no replacements so I did the same fix like in post one... thought i have it fixed when it turned on but it turned off in a few seconds... now the red led stays on but the screen keeps shuting down after 2 seconds... did I put in the wrong transformer, does it need to have both secondaries at 1,21 kOhm cause I thought the most important thing about transformer is primary/secondary ratio

[selldoor]

Re: Samsung 23" LCD P2350 Inverter Repair

AM4512C is available on ebay the important thing on inverter transformers is that the
secondary windings should measure the same (within 3%) if there are two secondaries on one transformer. If the transformer has only one secondary then it should measure the same as the other transformers if there is more than one lamp.
If there is a number of transformers ,as is often the case on a tv inverter board, each transformers pair of secondaries should be the same and every transformer should be the same.

[CroTech]

Re: Samsung 23" LCD P2350 Inverter Repair

for am4512c I would have to wait about month or two... Both secondaries ar exactly at 1,68kOhm and the one I replaced had one at 1,21kOhm and other at 98kOhm. What could be the problem now?

[selldoor]

Re: Samsung 23" LCD P2350 Inverter Repair

As I said in your other thread and someone else also mentioned we 'think' you have to replace like with like ie1200ohms with 1200 ohms OR perhaps change some resistors or something so that the protection doesnt kick in and switch the lamps off.
Unfortunately I dont know enough to be certain.
Perhaps ask the question in general electronics. eg "can I replace a faulty inverter transformer with 1200 ohm secondaries with a transformer with 1600ohm secondaries.
or visa versa and if not why not?

[CroTech]

Re: Samsung 23" LCD P2350 Inverter Repair

I will try posting it