emachines E230H monitor - worth fixing?

[shewb]

Hi, I'm a newbee, first time fixing a monitor. I have some knowledge of basic electronics, and I'm learning quickly from this terrific forum.
This monitor went black. I didn't test it with a flashlight, though. Upon disassembly, there were two bulging caps on the power board (photo is of caps after removal, 1000uF 25V). I acquired two replacements from Scott at LCDalternatives and replaced them.
When I tested the monitor, it still didn't work except power light, and after 30 seconds there was a small pop and whiff of smoke. I am attaching photos of the power board front & back. On the back there is a component (google says it's a logic gate, APM4548A) with a small melted hole in it. (photo also attached)
Yes, I probably should have replaced all six caps before testing.
Should I spend some more time fiddling with this, or throw in the towel?
Do you guys need more info?
Thanks!

[Chungalin]

Re: emachines E230H monitor - worth fixing?

It's an Anpec APM4548AK, dual complementary MOSFET. It has one N-channel and one P-channel MOSFET in a single SOIC-8N package. Typical from CCFL inverter. You'll easily find its datasheet. You can replace by same part OR another SOIC-8N (or SOP-8) complementary mosfet with same ampers/voltatge characteristics.

Worth repairing? You have the answer. If you're concerned with electronics waste plague, and if this monitor was satisfactory before failing, then definitively it's worth repairing.

On the other hand, it will depend on your tools, skills and resources. You can always order the parts and they will be quite cheap.

[shewb]

Re: emachines E230H monitor - worth fixing?

That's somewhat encouraging, Chungalin.
I would like to proceed, if I can get some idea of the likelihood of success.
If I replace the remaining four caps and the MOSFET, what are the chances that this thing is going to work?

[Chungalin]

Re: emachines E230H monitor - worth fixing?

I wouldn't care about other capacitors at this moment. I'd focus on replacing the dual mosfet and checking for short diodes. After this, if you do this right, the worst problem you can encounter is that some CCFL is bad or needs refurbishing. After mosfet replacing, try to power on with unplugged lamps. If nothing burns again, then try again with lamps.

You don't need to replace APM4548AK with same part, if you can't find it. Any SOP-8 complementary mosfet with ±30V / +7A / -6A will do the same. Some that I have found in other monitors:

P2103NVG Niko Semiconductor
MDS9651 Magna Chip
AO4600 Alpha & Omega (only -5A on P-channel, but will work anyway)
FDS8962C Fairchild
FDS8958A Fairchild
FDS8858CZ Fairchild
...

[shewb]

Re: emachines E230H monitor - worth fixing?

checking for short diodes?
Are the diodes part of the mosfets or nearby?
(You're reaching into the limits of my knowledge...)
I have a V-Ohm-Ammeter only.

I ordered ten mosfets to play with.
Thanks for the help Chungalin!

[Chungalin]

Re: emachines E230H monitor - worth fixing?

You should have a DMM with diode testing capability. That’s the most elementary tool to perform basic checks on semiconductors.

[shewb]

Re: emachines E230H monitor - what do I do now?

OK, I finally got around to replacing the MOSFET with a melted crater on the top. The solder job isn't pretty, but it looks OK with no shorts. Dang, those pads are tiny!
Then I re-assembled the monitor and powered up.
The screen was covered with horizontal streaks making everything illegible -
But after it warmed up (a good hour), the streaks settled down so that everything is legible, but very grainy, and the image shakes up & down a mm or so all the time.
So far I only replaced the two caps on the power board that were obviously failed. Should I replace all the rest?

[Chungalin]

Re: emachines E230H monitor - worth fixing?

Looks like a panel fault. How is it possible that it started with a power supply fault and now it has a panel problem? Did you handle the panel correctly? You have to be very careful when holding the bare LCD panel, so not to touch the top PCB with flexible bonds to the LCD glass.

Try to reseat LVDS cable. Replacing more caps won’t solve those horizontal lines.

[shewb]

Re: emachines E230H monitor - worth fixing?

I was pretty careful handling the panel. There is an extra metal cover on the top PCB of the panel, see photo, I removed it initially, then replaced it before I continued.
So, I re-seated the ribbon connector at the top, and nothing changed. Is that the LVDS cable?
The monitor was still warmed up, so the image is still just grainy and shaky.
I haven't replaced the rear plastic cover yet.
What now?

[Chungalin]

Re: emachines E230H monitor - worth fixing?

Post a picture of screen effect.

[shewb]

Re: emachines E230H monitor - worth fixing?

I re-checked the connections and let the monitor cool off so I could eat lunch.
When I powered up again, the image was really poor at first with most of the screen black and a few blinking horizontal streaks. After it warmed up, the streaks mostly disappeared, and just the graininess and jittering up & down remained. Then I took a photo.
Notice the black specks all over the Windows 10 logo. Also, there is a white streak at the top of the screen. The image was jittering.
I hate to say this, but right now as I write this, the image looks perfect HA!!
It probably won't stay that way...
When I initially took apart the monitor, there were a few foil tapes holding wires in place. Are they important, like for shielding?
Also, there was a rubbery pad between the PCBs and the display, you can see in the previous photo where it had slipped out of place. It looks like a refrigerator magnet material. Where does it belong?
Why does the monitor need to warm up before the image stabilizes?
Thanks again Chungalin! Why doesn't anyone else chime in here?

[Chungalin]

Re: emachines E230H monitor - worth fixing?

Aluminium foils are recommended for improving shielding, but should not be harmful if removed.

Black plastic sheet is intended for preventing any accidental contact between the boards and LCD panel. Must be placed again in the same position.

Effect on screen indicates two different problems related to panel. Top horizontal white line (plus image shake up-down from that line to bottom) means to me faulty gate driver, generally unrepairable. But the dark zones indicate a global color/gamma processing fault, related to T-CON. Since this panel doesn’t have detachable T-CON, it’s a no-win game. Let’s see if someone else has another opinion.

Can you tell panel model? It’s on the sticker that says "LG Display".

[shewb]

Re: emachines E230H monitor - worth fixing?

Yeah, it says LM230WF1 (TL) (A5)
And, it looks like as long as I keep is warmed up, it performs OK.
If the repairs are difficult, I think I'll throw in the towel...