Hyundai L90D+ inverter mosfet problem

[retiredcaps]

Re: Hyundai L90D+ inverter mosfet problem

Finally got to sit down with the monitor. Here is what i found:
S1 - D1 > 100k
G1 - D1 > 200k
S1 - G1 > 200k

S2 - D2 = 101k
G2 - D2 = 122k
S2 - G2 = 19k

These are in-circuit results. I can pull the chip and retest it you think that would give more valid results.

Those results indicate that your FETs are good. No need to replace them or test them out of circuit.

As mentioned, i have 5 of these I'd really like to get going, so any good ideas will be greatly appreciated.

If this were me, I can see 2 approaches.

1) Since I have 5 identical monitors, I can take them all apart and try to make one good one by swapping boards, cables, lcds, panels, etc until I make a working one.

With this good one, I can then use this as a baseline for voltage measurements and something to compare to. I also have a known good working configuration.

This would make troubleshooting the other bad ones much easier.

2) Randomly pick 1 of the 5. Troubleshoot the 1 logically and methodically.

If you choose 2, post clear focused pictures AFTER reading

https://www.badcaps.net/forum/showthread.php?t=1868

Please do not post pictures inline.

Take your boards to a window on a sunny day, turn flash off, and use macro mode. Take a top down view of all your boards (front and back). Make sure the photo is legible so that we can read the PCB printing clearly. A shutter speed of 1/125 or faster will produce nice clear focus pictures. Try to get a photo that is 2000x2000 resolution or as close as possible.

Here is an example of the pictures we want.

https://www.badcaps.net/forum/showpo...94&postcount=1

[URAD_Harvey]

Re: Hyundai L90D+ inverter mosfet problem

I loved my L90D+ when it was working - so did my son and one of my clients.

Now I have 3 dead ones and want to fix 'em up.

Over the years 3 of the 4 have been sent back for warranty repair for the same problem. But now these 3 are out of warranty.

The power/inverter board is hard to find.

When I got my monitor back from repair, I noticed the brightness no longer worked correctly - soon after (within months) it failed again. I took it apart and found a dead APM9932. I remembered that one of the other monitors had an exploded ICE2AS01, blown fuse, fried 04N60C3 Mosfet and who knows what else, but it had one good APM9932. So I unsoldered it and put in on my other one. The brightness still did not function correctly, but it was usable. Again, it failed after a couple of weeks. So, this time, I wanted to really get a handle on the whole picture and I hunted all over for manuals or schematics. I found some things that were 'close' from the chip manufacturer suggested applications, but I wanted the real deal. Finally, just this week, I took the time to make a schematic. Still needs a little work on the cap values, but the finished product is so close to the manufacturer's recommended application, the caps values from that are probably close enough.

The LM358 OpAmp is used to control the Dim feature of the monitor which is done by PWM all built into the OZ960SN features (pin 14). I suspect either this section has a problem, or the DIM signal from the Processor board is faulty. I haven't got that far yet, just finished getting the schematic done so I can actually do this justice

My guess here, is that the APM9932 cannot handle the continuous load at full PWM duty cycle (full brightness) for long durations. More than likely the airflow is insufficient to cool the device under this type of load as the board is encased in a plastic protector with just a few holes which is then nestled into a confined metal casing with just a few more holes in it and all driven from convection. I think the heat is getting trapped in there and the APM9932's are paying the price with their lives. The board I have with the shorted U6 P-channel has discoloration on the opposite side for both chips from overheating the FR4. For us DIY, it may be prudent to devise some type of heat sink for these little workaholics - as long as the lamps are lit, they are switching.

=================

I had thought with that old monitor with everything fried, that perhaps I could strip everything off and play around with a clear glass LCD monitor - no inverter needed. So I took an old computer power supply and rigged it up to the Processor Board to see how much light would pass through from my desk lamp. Sadly, I discovered that the LCD matrix electronics is bad on that one, so it really took a hit when the power supply section blew up. Interestingly, the Processor Board still works . But I was able to prove (at least to myself) that the processor and LCD Matrix electronics will run off the computer supply. I did this on my other monitor that I want to fix.

I wonder if there is a way to retrofit these for LED back lighting

[pcton]

Re: Hyundai L90D+ inverter mosfet problem

I just got one of theese. Same problem too... no visible damage on board so far. Seems to be cummon failure. I can't fix more than bad caps without guidance tho. Standing by...

[retiredcaps]

Re: Hyundai L90D+ inverter mosfet problem

I just got one of theese. Same problem too... no visible damage on board so far. Seems to be cummon failure. I can't fix more than bad caps without guidance tho. Standing by...

Post pictures of your boards so we can see the specifics of your board. Do not post images inline (use manage attachments) like the OP in post #1.

Describe in detail what is wrong with your lcd. Hookup a working computer to the monitor. Does the power LED come on? If you shine a flashlight, can you see the display?

[pcton]

Re: Hyundai L90D+ inverter mosfet problem

Post pictures of your boards so we can see the specifics of your board. Do not post images inline (use manage attachments) like the OP in post #1.

Describe in detail what is wrong with your lcd. Hookup a working computer to the monitor. Does the power LED come on? If you shine a flashlight, can you see the display?

Led goes...
100ms orange+blue led (led test?), speakers clicks
~5s blue led
sometimes 200ms orange led (for no-signal)
but then power goes off for a second
and repeat...

I might see a dim back light struggling.

Time to defuse...

[PlainBill]

Re: Hyundai L90D+ inverter mosfet problem

Led goes...
100ms orange+blue led (led test?), speakers clicks
~5s blue led
sometimes 200ms orange led (for no-signal)
but then power goes off for a second
and repeat...

I might see a dim back light struggling.

Time to defuse...

Textbook description of bad capacitors.

PlainBill

[pcton]

Re: Hyundai L90D+ inverter mosfet problem

Textbook description of bad capacitors.
PlainBill

My caps seems ok... http://kauhava.no-ip.org/pcton/hyundai/

U4
G2 -> D2 = 42 Ohm

U6
G2 -> D2 = Over 9000k keeps rising

(on-board results)
Wich one is bad?

[jetadm123]

Re: Hyundai L90D+ inverter mosfet problem

My caps seems ok... http://kauhava.no-ip.org/pcton/hyundai/

U4
G2 -> D2 = 42 Ohm

U6
G2 -> D2 = Over 9000k keeps rising

(on-board results)
Wich one is bad?

First of all, if you posted your photos on a different site, few members will go to that site for fear of computer viruses. Please post your photos per PlainBill's links on post #26.

You provided only partial readings. I think previous members checked U4, U5 and not U6. These are duo mosfet packages. Look at the datasheet provided by retiredcaps in post #20. And you should get 6 results like post #26.

If you do not understand, PLEASE reread this entire thread.

[camra88]

Re: Hyundai L90D+ inverter mosfet problem

My problem is that the backlight just won't turn on. When the computer is in standby, the monitor's LED turns orange, as usual. When it gets a picture, the LED turns blue, as normal.

I have tested the both of the dual-MOSFET APM9932 packages, and the lowest resistance reading I got was ~20k ohm. According to previous posters, they "pass the test."

Next, I closely examined every capacitor I could find on both sides of the board ("FeeLux", power board) and was unable to visually identify any potentially bad capacitors.

I tested the fuse, and it is not blown.

I also do not see any burn marks on the FR-4 (neither sides).

What else could the problem be? The monitor worked this morning, then goto use it a few hours later and the backlight doesn't come on.

[jetadm123]

Re: Hyundai L90D+ inverter mosfet problem

My problem is that the backlight just won't turn on. When the computer is in standby, the monitor's LED turns orange, as usual. When it gets a picture, the LED turns blue, as normal.

I have tested the both of the dual-MOSFET APM9932 packages, and the lowest resistance reading I got was ~20k ohm. According to previous posters, they "pass the test."

Next, I closely examined every capacitor I could find on both sides of the board ("FeeLux", power board) and was unable to visually identify any potentially bad capacitors.

I tested the fuse, and it is not blown.

I also do not see any burn marks on the FR-4 (neither sides).

What else could the problem be? The monitor worked this morning, then goto use it a few hours later and the backlight doesn't come on.

Sounds like you're getting the 5V output, since you're getting a power light. I bet that if you shined a flashlight against the screen, you'll see an image. That leaves the 12-14V that powers the inverter section. Referring to the first photo in Post #1 of this thread, there are two heatsinked diode packs, D2 and D3. The center leg is the voltage output. One outputs the 5V and the other 12V. I don't know which is which. Take your meter and measure for the 12V.

[camra88]

Re: Hyundai L90D+ inverter mosfet problem

Is there a way to measure that with out the risk of death?

[retiredcaps]

Re: Hyundai L90D+ inverter mosfet problem

Is there a way to measure that with out the risk of death?

Put your black probe in COM. Red probe in Volts. Put your multimeter on 20V DC (if manual).

Put your black probe on a ground screw. Put your red probe on the middle pin of the dual diodes. It should read 5V DC or 12V DC.

PS. This is fairly low voltage. Measuring the biggest capacitor could be nasty as there is 165V DC. In your case, since you are getting a power LED indicating 5V DC, this implies that the biggest capacitor seems to be working fine.

[camra88]

Re: Hyundai L90D+ inverter mosfet problem

The one closest to the center of the board is the +12 volt supply. The one nearest the edge is +5 volts. It appears both are working correctly.

Is there a ghost in the monitor or something???

[retiredcaps]

Re: Hyundai L90D+ inverter mosfet problem

The one closest to the center of the board is the +12 volt supply. The one nearest the edge is +5 volts. It appears both are working correctly.

Can you post clear focused pictures of your board like the OP in post #1 (via attachments and not inline)? Sometimes manufacturers make small changes to the board and those changes could make a difference.

Also just to clarify, when you power on/off the monitor now, do the backlights flash even briefly? Or do they stay off the entire time?

[camra88]

Re: Hyundai L90D+ inverter mosfet problem

I have taken the pictures. See attached.

The back light wont even turn on when I cycle the power to the monitor. Either via power button, or unplugging and plugging back into the outlet.

I put the monitor back together to test this, and the problem still persists.

What's my next step?

[retiredcaps]

Re: Hyundai L90D+ inverter mosfet problem

The back light wont even turn on when I cycle the power to the monitor. Either via power button, or unplugging and plugging back into the outlet.

1) See the Samxon caps at C52 and C22. Are they GF series? The GF series is highly suspect.

2) Can we get another clear focused closeup pic of the area highlighted in yellow?

3) What is the part number of that IC above the FreeLux writing on the back side? It might be OZ960SN, but would like clarification.

[camra88]

Re: Hyundai L90D+ inverter mosfet problem

1) The capacitors appear to be GF series. They read:

GF (M)
TOA
105*C8

2) I'm not quite sure what you mean by the area highlighted in yellow. I'm assuming your talking about the transformer? See attached image.

3) The backlight IC driver is indeed 0Z960SN.

[retiredcaps]

Re: Hyundai L90D+ inverter mosfet problem

1) The capacitors appear to be GF series. They read:

GF (M)
TOA

2) I'm not quite sure what you mean by the area highlighted in yellow.

1) I would replace those caps. I have personally seen Samxon GF caps from 2008 go bad and don't trust them even though they are not bulging. For a replacement, I suggest Panasonic FM

http://search.digikey.com/scripts/Dk...name=P12383-ND

You can remove that white glue holding down the Samxon GF caps and not have to replace it.

2) Sorry, I forgot to attach the pic of the area. Try to get the pic close to 2000x2000 as possible.

[camra88]

Re: Hyundai L90D+ inverter mosfet problem

I do not have any sunlight currently to take good pictures, hopefully these will do. There are 2, hopefully you can make out everything in the area.

Other than replacing those caps, what else could the problem be?

[retiredcaps]

Re: Hyundai L90D+ inverter mosfet problem

Other than replacing those caps, what else could the problem be?

In that yellow boxed area, you can, with power off and unplugged, test every component for shorts. You can test all the components marked Q, D for shorts.

For the C, SMD caps, you can see if they are shorted?

For the R, see if the resistance matches the expected value.