iiyama ProLite X486S dead - psu / inverter issue

[kbs1]

Hello, I'm looking for some help with my 19 inch LCD monitor.

My iiYama ProLite x486s monitor has just stopped working. I have tracked it down to be (probably) power supply / inverter board issues.

The monitor is dead. When assembled (in plastics), it only shows orange (standby) LED. It's supposed to show blue led when ON. This led shines, but shines faintly, so that it's invisible through plastic.

When disassembled, the blue led is visible - faint - and display is dead, no picture.

I have found another thread that describes dry solder joints around L101. My board had many dry joints, so I resoldered L101 (on mine it's L901) dry joints and also resoldered any other dry joints that I could find. No luck, still the same. Capacitors are visually OK (not bloated). Board is visually OK. Transistors are not shorted (tried to measure them and some resistance always popped up).

The problem, I suppose is that on the main connector (to monitor main board), the voltage on pin 12 is 12V when in standby - however when turned on (faint blue led shines), the voltage drops to 9V. On pin 3 (5V line I suppose), the voltage drops from 5V to 1V. I think the monitor wants to display "no signal message", because after a while it goes to standby again (strong orange led shines) and the voltage again rises up to 12V/5V on said pins of connector.

I'm just guessing here. Also, when I press the power switch on the monitor, the PSU (don't know which part) makes a high pitch / frequency noise for about ~2 seconds [voltage is now STILL 12V/5V BUT blue led shines faintly anyawy], after this period the noise stops (complete silence) and the voltage drops. After a while (~10s) the monitor goes to standby, no noise from PSU any more, and strong orange led shines. Voltage also rises to 12V/5V.

This repeats when I turn it off via power button and on again.

It just completely died all of the sudden. No issues before whatsoever. Any help on what parts to check or what could be the problem would be really great.

Also, the psu part number is 715G1236-3-AS, but I have been unable to find a datasheet for it. I do not even know the actual pinout for the main board connector, so maybe the voltage drops are normal.

Also, there is no backlight, nothing.

Detailed pictures of boards attached.

Thanks!

[selldoor]

Re: iiyama ProLite X486S dead - psu / inverter issue

Hi bit too much flash/glare on some of the pics.
Are the caps on the powerboard united chemicom?
What make are the caps on the main board.

[PlainBill]

Re: iiyama ProLite X486S dead - psu / inverter issue

Other than the glare, an excellent set of pictures. Certainly they give a good starting point for measurements. And your initial observations were a good start.

My suggestion is to mount the power supply in place using all the screws, but leave the ribbon cable to the signal board disconnected. Measure the voltage across the pins of the very large cap - it should be 1.4 x the AC line voltage - 165 volts in North America, 330 volts in many other parts of the world. Next, measure and report the voltages on each of the 12 pins in the connector to the signal board.

Now, with the cable to the signal board hooked up, but the LCD panel disconnected and the power LED glowing amber (standby), repeat the above measurements. And lastly, repeat them with the power LED glowing blue (On).

By your description I suspect either the inverter or the LCD panel is producing an excessive load. As an alternate explanation, it is possible a bad cap could be responsible, although all look fine.

PlainBill

[kbs1]

Re: iiyama ProLite X486S dead - psu / inverter issue

Hello, thanks, those were shot with my Sony Ericsson C905, still a very nice mobile with a very good camera ;-) If you'd like, I can take photos without the glare by using no flashlight and shooting in direct sunlight.

I measured the voltages as you said, and:

a) with everything disconnected (even the high voltage backlight leads) -> only the power board connected in 240V AC socket (measured using multimeter)
- voltage across the pins of very large cap - 310V DC (and my multimeter also measured 681V AC, but that's probably irrelevant/wrong because there should be DC voltage on the capacitor [i think])

12 pin connector (I did this by placing negative voltmeter lead to pin 1 [GND, also marked on the wire by red dots], and positive lead to each other pin on the connector):
pin 1 => GND
pin 2 => 0V
pin 3 => 4.70V
pin 4 => 4.70V
pin 5 => 0V
pin 6 => 0V
pin 7-10 => not connected
pin 11 => 0V
pin 12 => 11.99V

b) with just backlight high voltage lines connected
- exactly the same readings on the connector, but there are only 302 volts DC across the capacitor

c) with signal board, backlight connected and LCD panel disconnected (monitor still tudned off - did not press power button - no light shines)
- 302V across the capacitor

pin 2 => 3.12V
pin 3 => 5.06V
pin 4 => 5.06V
pin 5 => 0V
pin 6 => 0V
pin 11 => 0V
pin 12 => 12.87V

d) everything connected, LCD panel disconnected - monitor in standby (amber led shines)
- 302V across the capacitor

pin 2 => 3.12V
pin 3 => 5.06V
pin 4 => 5.06V
pin 5 => 0V
pin 6 => 0V
pin 11 => 0V
pin 12 => 12.87V
(exactly the same readings)

e) everything connected, LCD panel disconnected - monitor on (faint blue led shines)
- 303V across the capacitor

pin 2 => -0.80V (???) - the voltage rises back to +3.12 after the monitor goes back to standby - leads are placed correctly and I can see the voltage rise from -0.80V to 3.12V in real time
pin 3 => 1.03V - rises to 5.06V on standby
pin 4 => 1.03V - rises to 5.06V
pin 5 => -3.99V - drops to 0V on standby
pin 6 => -3.99V - drops to 0V on standby
pin 11 => -3.99V - drops to 0V on standby [as pins 5,6]
pin 12 => 8.82V - rises to 12.87V

e) everything connected (including LCD panel), but backlight disconnected - monitor on (faint blue led shines)
- the same situation (low/negative voltage)

e) only power and signal board connected (backlight and LCD disconnected) - monitor on (faint blue led shines)
- the same situation (low/negative voltage)

So based on my tests, what is wrong? We can observe that once I'm able to turn the monitor on (so main board is connected -> button works), voltage problem occurs, no matter what else is connected (the panel or backlight).

I'm still guessing the PSU / inverter board, but why?

Selldoor - I am unable to find any brand information on the capacitors on the main board or the power board, attached are some labels I was able to read off and seemed to make sense (they looked like model numbers)

[selldoor]

Re: iiyama ProLite X486S dead - psu / inverter issue

Hi - Hermei caps are poor and will probably need replacing The EL and TL may be
Elite and again are poor. The KY ones on the power board maybe Korea Chemicon
not much info on them but id guess not very good. The ones on the Main board have logos but I cannot make them out - can you do a side picture of each one.
There are a few posts on other iiyama monitors which had these caps as well.

Late Edit - two small caps near the BIG cap on the power board are also important ones - they also dry out as they are near the heatsink
if you can detail these as well

[kbs1]

Re: iiyama ProLite X486S dead - psu / inverter issue

Oh, sorry, I forgot about those. They are:
- KME 50V 10uF (the nearest one)
- KME 50V 22uF (the other one)

Below are enclosed close up pictures of main board caps, there are 4 brands of capacitors on the board:

- first is "TL" in circle
- second is "EL" in circle
- third is looks like an eye with three eyelashes (on closeup - nearest capacitor on the photo - sorry for quality) [2 pieces on whole board, second is to the right of the brown capacitor] - the same capacitor (voltage & capacity)
- the fourth brand is HERMEI - only one capacitor on board - sorry for closeup quality (my camera's macro is not the best)

[selldoor]

Re: iiyama ProLite X486S dead - psu / inverter issue

Pics will do ok for this.
Probably a poor set of caps all round apart from the Rubycon.
KME is probably Samyoung or Korea chemicon - poor
TL is a manufacturer in its own right but cant find if good or not.- probably poor
EL is probably the other way up - I see it as a black F in a white T in an elipse. cant find it anywhere.
Eye with 3 eyelashes is probable WC (a w on top of a c) and is related to Hermei so poor.
Plainbill may be able to identify EL and may suggest which to replace first to try and get it going if he thinks caps are the problem.
In the UK I would just replace all as on these boards there are not many and they are relatively cheap.

[jetadm123]

Re: iiyama ProLite X486S dead - psu / inverter issue

I would suggest you test the 8-pin surface mount transistors Q204,208,209 and 210 located on the bottom of your power board for shorts. What are their part numbers?

[kbs1]

Re: iiyama ProLite X486S dead - psu / inverter issue

Selldoor - I'll check in my local store if I can find a better brand of capacitors, which I'm not sure. But that will not be before monday, because they are closed on weekends. Last time I bought capacitors from them (to fix my LG LCD adapter), they worked OK but the adapter had burnt a week later.

jetadm123 - How do I test those out using simple multimeter? I have exactly the one attached in the picture below. It has PNP / NPN testing functions but I am not sure if I can use that.

Their part numbers are the same on all four:
45120
AA6FZ

[kbs1]

Re: iiyama ProLite X486S dead - psu / inverter issue

Selldoor - I have located my old LG Flatron L1960TR-BF 12V 3.5A adapter (the monitor now runs on 15V 3.5A notebook charger with 3x 6A diodes on positive 12V lead with CPU cooler on top of them [just heatsink] connected in series before input to the monitor - works like a charm ;-) Input voltage with warmed-up diodes is 12.03V

Anyway, the capacitors I bought from my local store are:
- 25V 1000uF brand "SAMWHD"
- 25V 10uF brand "Aishi"
- 50V 22uF brand "TK" in circle

Are those any good or should I ask them for better quality capacitors in case we decide to replace them?

[jetadm123]

Re: iiyama ProLite X486S dead - psu / inverter issue

Selldoor - I'll check in my local store if I can find a better brand of capacitors, which I'm not sure. But that will not be before monday, because they are closed on weekends. Last time I bought capacitors from them (to fix my LG LCD adapter), they worked OK but the adapter had burnt a week later.

jetadm123 - How do I test those out using simple multimeter? I have exactly the one attached in the picture below. It has PNP / NPN testing functions but I am not sure if I can use that.

Their part numbers are the same on all four:
45120
AA6FZ

Unfortunately, most local stores do not sell low-esr caps, which are required for these type of repairs. The type of of caps you need are listed here:

https://www.badcaps.net/forum/showthread.php?t=2280


I cannot seem to locate the datasheets for the part number you listed. If we figure out what the actual part number is, then you can test them per retiredcaps guide:

https://www.badcaps.net/forum/showthread.php?t=10419

[selldoor]

Re: iiyama ProLite X486S dead - psu / inverter issue

I was just going to say- see what they have got then post details on here.
Is it SamwhD or SamwhA - samwha are poor. Samwhd probably related
Aishi - not much known but probably poor
TK if like attached are Good!


I have been trying to find data sheet for the ICs but have drawn a blank
hope they test ok.

[retiredcaps]

Re: iiyama ProLite X486S dead - psu / inverter issue

12 pin connector (I did this by placing negative voltmeter lead to pin 1 [GND, also marked on the wire by red dots], and positive lead to each other pin on the connector):
pin 1 => GND

Just one clarification. How do you know Pin 1 is GND? Is there some marking or legend that says it is GND? I can't spot anything from the pictures?

[retiredcaps]

Re: iiyama ProLite X486S dead - psu / inverter issue

jetadm123 - How do I test those out using simple multimeter?

Their part numbers are the same on all four:
45120
AA6FZ

See section on mosfets at

https://www.badcaps.net/forum/showpo...4&postcount=19

[retiredcaps]

Re: iiyama ProLite X486S dead - psu / inverter issue

The KY ones on the power board maybe Korea Chemicon
not much info on them but id guess not very good.

Small correction above to selldoor's post. KY is made by United Chemi-con, a Japanese company, and are good low ESR caps. UCC can be usually identified by the their brown color, a "crown" symbol, and a "Y" or Mercedes Benz vent.

[kbs1]

Re: iiyama ProLite X486S dead - psu / inverter issue

Hello, pin 1 looks like ground, the wire has red dots on it and the connector is marked by black marker at pin 1. I also tried measuring the voltages by placing negative lead of my multimeter to a nearby transistor heatsink, and positive to each pin. Pin 1 had 0V (bud did not "beep", so no short circuit). I thought this was normal.

[jetadm123]

Re: iiyama ProLite X486S dead - psu / inverter issue

Whew! Looks like the Toshiba AD174TW monitor uses a similar power supply (715G1236-1-AS). Not sure what the differences are, but the 4 8-pin mosfets might be: P3503QVG. Schematic is here:



To test: with power off, set your meter to 200ohms and place your probes across:

S1-G1
S1-D1
G1-D1

S2-G2
S2-D2
G2-D2

Perform this test for the other 3 transistors. If you see approx 0 ohms for any of your readings, then you have a short.


Also, on the 12-pin connector, looking at the schematic pin 1 on the power board is identified as on/off, not ground.

[retiredcaps]

Re: iiyama ProLite X486S dead - psu / inverter issue

Hello, pin 1 looks like ground, the wire has red dots on it and the connector is marked by black marker at pin 1.

Humor me, and redo the "negative voltage" measurements again this time using a ground screw on the power board for your black probe (GND).

[kbs1]

Re: iiyama ProLite X486S dead - psu / inverter issue

selldoor - My TK capacitors are not like that. They have a "TK" mark in circle and are blue. And the other ones - they are "samwha". So goes the capacitor quality at my local store Maybe that's why the LG adapter burned out a week later.

I have also tested all four Q's on the back site of the board with my multimeter set to "200" - resistance. I almost never got any reading, always just a bright flash and then immediately "out of range". I tested the 8-pin Q's by getting one lead on one leg on side A and other lead through all legs on side B. Then I moved the lead on leg 2 on side A and repeated the process. Therefore, I tested all possible combinations. I also tested the legs in all possible combinations on one side of the 8-leg transistor - same results. The other side legs were always soldered to the same PCB lead, so measuring there did show 0.1ohm resistance.

While I was measuring I checked the big transistor near big capacitor - setting 200 - never got any reading (out of range). Also tested with short circuit tester - did beep once for a very small split of a second - after that the resistance started to rise until out of range.

Other two "smaller" transistors - the same, except on one of them I can get a reading of ~94 ohms between pins 1 and 2 (pins 3 and 2 - out of range). The other one - always initial ~120 ohms, then jumps to out of range. On these two, pins 1 and 3 are soldered onto the same PCB lead.

Hope this helps. These readings do not tell me much at all

[kbs1]

Re: iiyama ProLite X486S dead - psu / inverter issue

Redone the measurements on P3503QVG's - they seem good. Always out of range measurement.

Main connector measurements - coming soon. I tried to use a ground screw the first time - but I could not even get a 12V measurement on pin 12 that way.