iiyama ProLite X486S dead - psu / inverter issue

[retiredcaps]

Re: iiyama ProLite X486S dead - psu / inverter issue

Never mind about #5, I saw that you already tested it.

[retiredcaps]

Re: iiyama ProLite X486S dead - psu / inverter issue

3) no, at all, no flash, nothing

1) If there is no backlight at all, then I would suspect those mosfets you tested. Namely, Q204, Q208, Q209 and Q210.

2) I believe the correct datasheet based on the power supply that jetadm123 found at



according to page 55 is AM4512C.

3) With that, we find



See page 1 pin assignments. Use that as your guide to retest the mosfets. Set your DMM to 200 ohms. Measure the combinations below.

S1-G1
S1-D1
G1-D1

S2-G2
S2-D2
G2-D2

Report all the above for each mosfet.

PS. "1" on the left hand side IS a reading on the multimeter. It means out of range (in this scenario it means the reading is greater than 200 ohms). There is no such thing as "no reading".

4) What is the part number of IC201 (on the backside)?

5) On the backside, see if there is a fuse marked as F902.

[kbs1]

Re: iiyama ProLite X486S dead - psu / inverter issue

Hello, did the tests:
1) wallpaper shows up, forever, visible only using flashlight

2) faint blue, should be strong blue (the led is so faint, that when the monitor is assembled, the led is invisible through plastic cover)
"a) does it change color at any point?"
- no, only when I disconnect the signal cable and monitor goes to standby, in that case it is strong orange (as it's supposed to be, visible through plastic when assembled)

3) no, at all, no flash, nothing

Editing material information: will not do that again What should I do next?

[retiredcaps]

Re: iiyama ProLite X486S dead - psu / inverter issue

There seems to be a lot of edits, contradictory statements, and mixed up test results.

So I suggest going back to the beginning and answering the following questions.

1) If you hookup a working computer with your favourite wallpaper and a known good VGA cable do you see

a) the wallpaper?
b) if yes, for how long?

2) What color is the power LED?

a) does it change color at any point?

3) Does the backlight come on?

a) if yes for how long?
b) if no, can you see your wallpaper in a very dark room or by shining a very bright flashlight at it from different angles?

Answering these simple questions above will direct you where to look for the problem.

PS. Making edits with material information is not recommended. Once I read a post, I usually don't go back and re-read it. If you edit a post for grammar, spelling, punctuation, then that is fine. If it is material information, I would prefer to see it in a new follow up post.

[kbs1]

Re: iiyama ProLite X486S dead - psu / inverter issue

According to https://www.badcaps.net/forum/showthread.php?t=8598 , I have tested all the small signalling transistors and other 3-legged small components (marked D...) for shorts - none found. I have also tested all diodes - one of them did give me a short circuit beep for a split second - then resistance started to grow. Is this normal? Do they need time to "start up"? The longer I "charged" the diode the longer it beeped when I reversed the multimeter leads - multimeter beeps and shows negative values on short circuit tester setting (ohms - is this possible?), which grow until eventually out of range when tested through one side - stops at ~700 when the diode is tested the opposite direction.

Affected diode is ZD904. No other diodes seem to display this behavior (they do not beep) - they are always ~650-700 ohms in one direction and out-of-range in another. The ZD904 is in the same range, so I'd say it's normal, it just takes it longer to get there (~5 seconds, of which the multimeter beeps for 1 second)

[kbs1]

Re: iiyama ProLite X486S dead - psu / inverter issue

I have taken out the logic board for the first time today - previously I have looked under it and there was nothing - only one rubber pad but no components. This turns out to be true - all components are on the front of the board. I have also checked all solder joints on the back now - seem fine. Pictures of the back side of the board attached.

I'd love if someone could came up with some new ideas on what to test. So far at this moment, I'm dry Regarding the capacitor possible problem, is there any way I can test them or do I have to try my luck? I'll go to the local store on monday to ask for low ESR caps and see if they have them.

I'll check the other thread you posted. Thank you all so far.

[selldoor]

Re: iiyama ProLite X486S dead - psu / inverter issue

yeh _ im well outside my comfort zone - I have been lucky so far in getting away with
replacing caps. I had worked out that cn701=cn901 but not sure where that led us.
I cant see a picture of the back of your main board? unless ive missed it.
Here is a post on a different machine which might be relevant -regarding on off transistor controllers www.badcaps.net/forum/showthread.php?t=8598
There is loads of good information in your thread and if some of the more experienced members pick it up im sure they will come up with more suggestions for you.

It may still be a cap problem as none have been replaced.

[kbs1]

Re: iiyama ProLite X486S dead - psu / inverter issue

As far as the IC's go on page 27, I can't locate any of that on the power board (there are only 8 leg and one big 20 pin IC on the back side).

On the logic board, no luck either (only 16-leg and 8-leg present).

As far as the other circuits go, those are all "700" parts. There are only 200 and 900 parts on the power board (CN202, C206, R225, C920 etc).

EDIT: on page 27, there is CN701. It just might be CN901 on my logic board. My board is marked 715G1548-1. The reference in phillips service manual we are using is marked 715G1558-1-IO. So the boards are similar.

Should I be looking for the circuits on the logic board?

EDIT2: yep, it's definitely logic board main connector (from power board). The pinout (as far as GND goes) matches - tested for continuity.

EDIT 3: found out (per page 27) that the CN901 pin 2 is "BL ON". This pin goes straight by the marked red wire to pin 1 of CN102 on the power board - if it is BL_ON, it had 4V during testing (when I initially measured the connector). So this should be OK!

EDIT 4: tested many many fuses, diodes, transistors and resistors on the logic board. No problems found. Don't know what to do next.

[kbs1]

Re: iiyama ProLite X486S dead - psu / inverter issue

Yeah. I have just disassembled the panel even more - bottom lamp looks completely OK, wires in excellent condition.

Also - the monitor died while I was away 5 minutes to get coffee, before that the backlight was perfectly bright, even so much bright that I had to use the monitor on 80% brightness. So I think the lamps will be OK. Also the monitor is 4 years old but had been used maybe 30 days at all (previous owner had problems with her pc all the time and was technically unskilled, so she almost did not use it). Therefore it is practically new.

Pictures of bottom CCFL attached.

Next I am going to test the circuits you mentioned.

[selldoor]

Re: iiyama ProLite X486S dead - psu / inverter issue

There's apost just gone up bbjunkie about no back light - smd fuse on back of board.
could there be one on this board.
also page 27 of the schematic has some circuitry switches on the back light if you can locate and check that.
If it is the ccfls I think you at least get a flash from ones that are good and youd have to be unlucky for all of them to have gone.

[kbs1]

Re: iiyama ProLite X486S dead - psu / inverter issue

492 and 493 ohm. Is there any way to check the CCFL's directly on the X486S? I read they can be measured somehow - is this always the case?

EDIT: I'll try to check the wiring first. It's only 4 wires - saw a recent LG thread on this forum that had broken CCFL wires.

[jetadm123]

Re: iiyama ProLite X486S dead - psu / inverter issue

Probably don't want to test voltages on those transformers as their secondaries can put out in excess of 1000V, which will probably burn out your meter. Instead, with power off and your meter set to 2kohm, try measuring the resistance of each secondary (the side that outputs the high voltage to the ccfl's) for PT201/PT202. There should be no more than 3% difference between the two. If they check good, then you'll have to figure out a way to connect your power supply to the ccfls on your spare panel. If its lights your spare panel, then you either have a bad ccfl or bad ccfl wiring on your X486S.

[selldoor]

Re: iiyama ProLite X486S dead - psu / inverter issue

error - sorry

[kbs1]

Re: iiyama ProLite X486S dead - psu / inverter issue

Based on that two of them have 13.04V on pin 3 and the other two have 13.19V on pin 3. What to check next? F902 is OK.

EDIT: both of their outputs go to the big PT201 / PT202 [transformer?]. Maybe I should check that part to see if there is any voltage behind it. But I'm afraid that would be high because there are markers of high voltage all over that part of the board - will wait for instructions.

[jetadm123]

Re: iiyama ProLite X486S dead - psu / inverter issue

Q209: if pin 1 is the one marked with a small dot, pin 2 is the opposite one, and pin 3 is the next one on the opposite side (in other words pin 3 is right next to pin 1), then that pin has -0.01V.

Please tell me if I can measure this with the backlight disconnected.

Actually, pins 1,2,3 and 4 are all on the same side, with pin 1 as you correctly identified marked with a dot. The pin numbering scheme goes in a "u" pattern. Refer to the inverter schematic, page 30

[kbs1]

Re: iiyama ProLite X486S dead - psu / inverter issue

The Q901 is in normal state, present and is black - on the photo it must be some camera weirdness. It really looks like a blob of solder but you can see it more clearly on photo 4 - also attached here.

[selldoor]

Re: iiyama ProLite X486S dead - psu / inverter issue

Off current thinking but can you look at Q901 - it looks like a solder blob but is shaped
like the Q902 transistor - has it been snapped off or is it just solder? The schematic whilst a guide has a few differences It has Q901 mentioned in the parts list but cant see it anywhere else.


Hah - found a pic with it on???

[kbs1]

Re: iiyama ProLite X486S dead - psu / inverter issue

Q209: if pin 1 is the one marked with a small dot, pin 2 is the opposite one, and pin 3 is the next one on the opposite side (in other words pin 3 is right next to pin 1), then that pin has -0.01V.

Please tell me if I can measure this with the backlight disconnected.

[kbs1]

Re: iiyama ProLite X486S dead - psu / inverter issue

I checked the fuse F902, found it, OK (shorted).

I'm looking at the TOSHIBA LCD-AD174TW service manual, page 41, section
2.) W / LED , No Backlight

The first step is "Check C928(+) =12V". I think this is a mistake. The word C928 does not appear nowhere else in the document. I can only locate C926, C927 and C929, and those 3 are listed on page 57.

So I have checked the C929 + and it's only 3.8V on one side and 2.48V on the other. Not 12V. Also the backlight is disconnected in this test, because the C929 is on the backside of the power board and the cables are not long enough. Logic board is connected though.

I'm going to test one of P3503QVG and see what happens.

EDIT: also, the power board itself is not connected to any ground with any screw. I don't know how, because as I said, C929 and P3503QVG's are on the back side of the board, and when screwed down, I can't get to them. Don't know wheter this is an issue or not. Logic board is gounded with screws and connected to power board.

[jetadm123]

Re: iiyama ProLite X486S dead - psu / inverter issue

The schematic shows a inverter fuse, F902. Try looking for it. It may or may not exist on your power board, since you have a different revision of the board. If you can't locate it, then pin 3 of each P3503QVG is connected to 12V. You only need to make one measurement because if you don't see the 12V, then you'll have to trace backwards to see why you are not seeing it.