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Crumbtrail TV Forums: TV Equipment: LCD TV Forum:
iiyama ProLite X486S backlight not working

 

 


kbs1
New User

Aug 20, 2012, 3:47 PM

Post #1 of 5 (2265 views)
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iiyama ProLite X486S backlight not working Can't Post

Hello, I have this 19 inch PC monitor IIYAMA ProLite X846S whose back light is not working. I can see the picture when I shine a flashlight on it. It was working and then one day poof - nothing.

I did a lot of short circuit troubleshooting on the inverter board only to find out nothing I checked is shorted - that includes diodes, mosfets, other transistors, random resistors and so on.

Now I know this is not a television but a PC monitor, but this forum seems to be most vivid and I feel there might be some good help around here.

In the time the monitor is broken I have already bought a new one, but having two monitors seems like a really good idea, so I'd like to repair it.

Now I have bought / did previously have this equipment:
1) a cheapo DMM (ohms, amps, voltage, diodes, continutiy)
2) 20MHZ oscilloscope
3) a good LCR meter (to test capacitors)
4) soldering iron

Now the backlight does not come on at all, never. I have even measured voltage coming directly to CCFLs when the monitor is ON (even accepting the fact that this could ruin my cheapo multimeter / whole monitor) and there are 0 volts AC and 0 volts DC measuring any possible combination of the 4 input pins.

So measuring that I have (possibly) ruled out the possibility of bad CCFLs, which leaves the the fault to be in one place - the power supply.

The board is visually undamaged, unburnt, and I can post detailed pictures, just let me know. I also have similar PSU diagrams and datasheets. The PSU part number is 715G1236-3-AS ver:A

Now, any ideas where to probe? I have only a very basic knowledge of electronics. Thanks :)


(This post was edited by kbs1 on Aug 20, 2012, 3:48 PM)



jts1957
Veteran


Aug 21, 2012, 4:31 PM

Post #2 of 5 (2249 views)
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Re: [kbs1] iiyama ProLite X486S backlight not working [In reply to] Can't Post

Which model of the 2 you mention is it?

DVM and CCFLs = Not a good idea.

Inverter board has VCC?
Inverter board has enable?


-------------------------
Location: Far, Far Away

(This post was edited by jts1957 on Aug 21, 2012, 4:36 PM)


arizanotlari
New User


Aug 24, 2012, 3:51 PM

Post #3 of 5 (2233 views)
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Re: [kbs1] iiyama ProLite X486S backlight not working [In reply to] Can't Post

Hello.

Does the inverter voltage transformers?
Do you have a voltage capacitors marked with a red circle?
values are marked in yellow leg transformers the same?

I hope you understand what I wrote, so I am not familiar to English.

http://arizanotlari.com/...es/715G1236-3-AS.jpg


kbs1
New User

Sep 11, 2012, 9:18 AM

Post #4 of 5 (2179 views)
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Re: [arizanotlari] iiyama ProLite X486S backlight not working [In reply to] Can't Post

Hello, the problem is there is only 13.18 volts DC on the inverter transformers. The driver chip IC201 only drives on output pin19, nowhere else. I do not know what is causing this.

The board is the same as you posted. I'd like to send you the datasheets but there is no option for attachments.


arizanotlari
New User


Sep 13, 2012, 10:34 AM

Post #5 of 5 (2162 views)
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Re: [kbs1] iiyama ProLite X486S backlight not working [In reply to] Can't Post

I think one of the backlight floresan failed.

 
 
 


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