Samsung 23" LCD P2350 Inverter Repair

[erbmit]

I bought this dead monitor on spec on Ebay.

Found the two tiny 8-pin SMD dual complementary AM4512C backlight inverter driver mosfets shorted all terminals. No other problems visible or measured. Removed the inverter transformer, and it seemed oddly wired to me but I couldn't fault it.

No replacement mosfets obviously available in Australia, so I bought 2 IRF540N and 2 IRF9540N discrete mosfets from Jaycar, & soldered them in, held only by the drain lead. Luckily there was space for them on the solder side of the board where the originals were.

The monitor has now been running for 5 days, no problems at all. Pics attached.

The originals were rated at 1W and 2W per mosfet, the replacements 130W and 140W per mosfet.

[Dgtech]

Re: Samsung 23" LCD P2350 Inverter Repair

It doesnt have to be pretty, it just has to work. Those mosfet's dont need a heatsink?

[jetadm123]

Re: Samsung 23" LCD P2350 Inverter Repair

Very clever fix!! Thanks for sharing.

[momaka]

Re: Samsung 23" LCD P2350 Inverter Repair

Those replacement MOSFETs are HUGE! That's a good thing, though; you definitely won't be seeing them burn out again. More likely the power supply will melt before these go bad .

[k0i_]

Re: Samsung 23" LCD P2350 Inverter Repair

iv'e got the same model... my problem is the backlight shuts off... i replaced all caps that i suspected, but still i get the same results... help

[k0i_]

Re: Samsung 23" LCD P2350 Inverter Repair

oh almost forgot... logic board also overheats....

[smason]

Re: Samsung 23" LCD P2350 Inverter Repair

That's one ugly repair, but I'm impressed. Nice job!

[Dgtech]

Re: Samsung 23" LCD P2350 Inverter Repair

oh almost forgot... logic board also overheats....

How was it determined that the board overheats? Do you smell anything burning, or does anything feel hot? You may have to replace the whole board but in a 23 inch LCD, it may not be worth it.

[whistlergonewild]

Re: Samsung 23" LCD P2350 Inverter Repair

I am having an issue with my monitor (samsung p2350) Turning off every 5 minutes, and turning back on a minute later. Very annoying. All the caps look good. Any sugestions, greatly appreciated.

[alexanna]

Re: Samsung 23" LCD P2350 Inverter Repair

I am having an issue with my monitor (samsung p2350) Turning off every 5 minutes, and turning back on a minute later. Very annoying. All the caps look good. Any sugestions, greatly appreciated.

I would suspect a problem with a solder joint, possibly around the SMPS transformer. I would try adding fresh solder to that area, see if anything changes.
For the monitor to shut off and restart one or more of the voltages to the logic board has to be changing, It's probably time to get the voltmeter out and try to identify which one.
Pictures would really be helpful; a good top down shot of all the boards high detail without a flash would be the best, using managed attachments.

[whistlergonewild]

Re: Samsung 23" LCD P2350 Inverter Repair

ok, so I tried to resolder the board, and it is still turning on and off. I find that it is shutting off sooner and now taking longer to turn back on. I have included some photos for you to view. Do you see anything wrong with any components??

This is the Samsung 2350, IP Power Board BN44-00297A

[whistlergonewild]

Re: Samsung 23" LCD P2350 Inverter Repair

Im now having even more difficulties. The monitor now only stays on for a minute and stays off for 4 min before automatically turning on again. This is reverse to how it was previously.

[Dgtech]

Re: Samsung 23" LCD P2350 Inverter Repair

Replace the five "Sam Young" midsize caps on the board and then try it again. These caps have gone bad for me in the past without bulging.
They look like they are 1000uF 10V caps. I'd replace these with 1000uF 16V's - if they will fit.

[pamr4]

Re: Samsung 23" LCD P2350 Inverter Repair

Check the inverter transformer secondaries. I must have around 1.21Koms each.

[whistlergonewild]

Re: Samsung 23" LCD P2350 Inverter Repair

Ok. So I hooked up a little 12V CPU fan to cool off the heat sink. It WORKED, the fan has cooled the heat sink and it doesn't turn off the monitor.

The only problem is the fan is really loud. Im thinking of putting some new silicone glue or thermal compound stuff behind the voltage regulator to see if this will help.

?Besides new glue, or thermal compound is there something else besides the fan that will disipate the heat better so my monitor will stop shutting down?

[Dgtech]

Re: Samsung 23" LCD P2350 Inverter Repair

Did you ever replace the capacitors? If not, this may be the reason the thing is heating up so much. If the regulator is heating up then it's having to release excess energy in the form of heat. You can put a fan on it and keep putting band - aid's on the original problem however, it will pop up again.

[whistlergonewild]

Re: Samsung 23" LCD P2350 Inverter Repair

Thanks DGtech,
Thanks for the quick reply. I had only replaced one cap but with no real results. The only reason is that I live in the mountains, and we don't really have anywhere to buy caps. I just noticed that I can buy them off this website so I may go along that route. I only need eight of them.

2x25v 1000uf
3x10v 1000uf
2x25v 47uf
1x16v 100uf

[whistlergonewild]

Re: Samsung 23" LCD P2350 Inverter Repair

Replaced all five of the 1000uf and the two 47uf....still the same problem. Could it possibly be the voltage regulator itself? If so how do i find this part number or what the rating is and where do i buy it?

[retiredcaps]

Re: Samsung 23" LCD P2350 Inverter Repair

Could it possibly be the voltage regulator itself?

On most lcd monitors, there are no voltage regulators on the power/inverter board. The voltage regulators are normally used on the logic board to convert 5V DC down to 3.3V, 2.5V and/or 1.8V DC.

In post #15, you talk about a small fan cooling off the heatsink. What heatsink are you referring to?

[whistlergonewild]

Re: Samsung 23" LCD P2350 Inverter Repair

I believe what I am talking about is the heatsink and voltage regulator.

You can see what I a calling the regulator attached to the heatsink. I believe it is inscripted with:
f DK16
S
65R