Hyundai L90D+ inverter mosfet problem

[selldoor]

Re: Hyundai L90D+ inverter mosfet problem

[QUOTE=Sharky-T;499901]

In post #1, it is picture 3. U5 to the right of the circled component. U4 is to the left of it. Both are 6 pins.

Hi... even though some years back, I wonder about the statement:

"Both are 6 pins."

On my board, U5 and U4 are 8 pins.

I am a bit confused.

There are 8 pins on the original picture - probably just a typing error.
retiredcaps also posted the datasheets which show 8 pins.

Retiredcaps used to help out on here for hours on end and it does go for the eyes. I personally work on a small laptop and can barely tell the difference
between the 6 and 8 on my keyboard .

Even if it was noticed later, one cannot amend posts after around 1 hour.

[Sharky-T]

Re: Hyundai L90D+ inverter mosfet problem

[QUOTE=retiredcaps;119680]In post #1, it is picture 3. U5 to the right of the circled component. U4 is to the left of it. Both are 6 pins.

Hi... even though some years back, I wonder about the statement:

"Both are 6 pins."

On my board, U5 and U4 are 8 pins.

I am a bit confused.

[Sharky-T]

Re: Hyundai L90D+ inverter mosfet problem

[QUOTE=retiredcaps;119680]In post #1, it is picture 3. U5 to the right of the circled component. U4 is to the left of it. Both are 6 pins.

Hi... even though some years back, I wonder about the statement:

"Both are 6 pins."

On my board, U5 and U4 are 8 pins.

I am a bit confused.

[rurban]

Re: Hyundai L90D+ inverter mosfet problem

I have a mildly off-topic contribution to this thread...
my L90D+ exhibited similar problems (power light flashed orange briefly then went back to blue, accompanied by a quiet clicking sound). I found a used power-supply in china and had it sent to me, which took 3 months. The PS was functional, but it already had a brown burn mark on the component side opposite one of the inverter MOSFETs.

I fashioned a heat-spreader and siliconed it to the PC-board to get the most out of the used PS. Picture below.

I also removed the plastic enclosure around the PS, and instead glued a piece of plastic to the back of the panel opposite the PS, in order to improve air circulation.

R. Urban

[retiredcaps]

Re: Hyundai L90D+ inverter mosfet problem

Check the resistance of the secondary for each inverter transformer. There should be no more than 3% difference between the two.

I circled the inverter transformer secondaries. With power off and lcd unplugged, set your multimeter to 2000 ohms (if manual).

Measure the resistance between the 2 red dots. Report measurement. Do the same for the blue dots.

[jetadm123]

Re: Hyundai L90D+ inverter mosfet problem

I replaced those caps with 25v, 330uF's. Problem remains.

I also noticed that when I first turn the monitor on, the backlight flickers for only a quick moment. I didn't notice it until I turned the lights off in the room.

After turning it on and off many times to observe this just now (about a dozen+ times), the monitor turns off once it attempts to power up the backlight. If I give it a minute, it will stay on again. I don't know if this means anything?

Knowing this, can I pinpoint the culprit?

Thanks

Since you're getting a flicker of the backlight before shutdown, this could be caused by:

1) Bad wiring to the CCFL tube(s)

2) Bad CCFL tube

3) Bad inverter transformer


To check the CCFL tube, you'll have to find a known good one and susbstitute for the existing tube.

Check the resistance of the secondary for each inverter transformer. There should be no more than 3% difference between the two.

[camra88]

Re: Hyundai L90D+ inverter mosfet problem

I replaced those caps with 25v, 330uF's. Problem remains.

I also noticed that when I first turn the monitor on, the backlight flickers for only a quick moment. I didn't notice it until I turned the lights off in the room.

After turning it on and off many times to observe this just now (about a dozen+ times), the monitor turns off once it attempts to power up the backlight. If I give it a minute, it will stay on again. I don't know if this means anything?

Knowing this, can I pinpoint the culprit?

Thanks

[retiredcaps]

Re: Hyundai L90D+ inverter mosfet problem

D14 and D16 (to the left of the 0Z960SN) -- i get a reading of 98 ohms across the two legs next to each other. They are the legs connected in parallel to a 390 ohm resistor (according to marking 3900).

Personally, I would change the caps first and retest. However, if you have really good soldering skills and can remove D14 and D16 without destroying them, you can test them out of circuit. In circuit testing can be affected by surrounding components.

My soldering skills for something that small dictates that I try new caps first.

[camra88]

Re: Hyundai L90D+ inverter mosfet problem

Results:

all caps and Q's are not short circuited. Including C22 & C52.

All resistors are within tolerances

All diodes? (D's) also pass this test, except for 2:

D14 and D16 (to the left of the 0Z960SN) -- i get a reading of 98 ohms across the two legs next to each other. They are the legs connected in parallel to a 390 ohm resistor (according to marking 3900).

I find this low, considering measurements taken off similar D's: D10 and D11 (they all have similar markings A7>) measured at 1k ohms. (390 || 1000) = 280 ohms. Is this a normal in-circuit resistance at those two nodes?

[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.

[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

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

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

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

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 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

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

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

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

[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.