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Old 11-25-2017, 04:40 AM   #1
Evekniv
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Default NEC MultiSync V552 power on and off (E-Waste Dumpster Diving)

Just collected a Nec Multisync v552 from the E-waste. well i was happy and all in heaven when i saw it!! omg is it for real? never in my lifte time i have seen that GOOD E-wast. most of it i find is just some smalls but god anyway.. but this was frickin awesome!!!

I hope i can get some advice here Or maybe it belong at the e-waste after all.

When power it on lcd blink and then it powering off, Nec has a diagnostic mod it goes into. 2 red flash and a solid. then repeats it.. i tried google the light code, but whit no luck..


PSU and Inverter (i think) and a overall pictures.

All help is met with big arms and a wide smile

Thanks..
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File Type: jpg Inver.jpg (601.4 KB, 77 views)
File Type: jpg PSU.jpg (169.2 KB, 59 views)
File Type: jpg overall.jpg (3.83 MB, 53 views)
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Old 11-25-2017, 05:01 AM   #2
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Default Re: NEC MultiSync V552 power on and off (E-Waste Dumpster Diving)

Multimeter shows right volt out on all pins on psu.
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Old 11-25-2017, 07:38 AM   #3
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Default Re: NEC MultiSync V552 power on and off (E-Waste Dumpster Diving)

Here is where I would start I would replace all caps that are 47uf and lower and see if it will stay powered up

You could take it little further and replace all caps that 100uf and lower and see if it makes a difference or not

If you have not solder much take your time when taking out those small caps it is very easy to pull the small pads right off the board i done a lot of these small caps and every once in awhile I will have ‘this happen to me
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Last edited by sam_sam_sam; 11-25-2017 at 07:46 AM..
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Old 11-25-2017, 08:40 AM   #4
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Default Re: NEC MultiSync V552 power on and off (E-Waste Dumpster Diving)

Thanks! ill do that.
good im a rc hobbyist, got all the tools. (almost)

wich tool is good to use to measure capacitor. as i understand you canot do it in circuit..

also, is it normal to hear the relay when it`s powering on

Last edited by Evekniv; 11-25-2017 at 08:43 AM..
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Old 11-25-2017, 08:57 AM   #5
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Default Re: NEC MultiSync V552 power on and off (E-Waste Dumpster Diving)

This is a monitor right? How much inches? First of all i don't think you have to change any caps for now, the second you have to put a valid source in the monitor for ex. pc image through VGA port, then switch on monitor and see if you can see the image for a moment, if yes then shut off and test those 3 whit fuses on the 1st picture board on the top.
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Old 11-25-2017, 09:17 AM   #6
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Default Re: NEC MultiSync V552 power on and off (E-Waste Dumpster Diving)

well i think your right its a monitor.. 55".
but i tryed it whit hdmi on my computer, and still the same. ill try whit vga asap

and wich 3 whit fuses*? i only see tow. (ceramic fuse) and if i done it right they where good.. multi and continuity test?
you meen on psu right?
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Old 11-25-2017, 09:53 AM   #7
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Default Re: NEC MultiSync V552 power on and off (E-Waste Dumpster Diving)

AAARGH!! Sorry not "whit".. WHITE fuses... i've already pointed at the first picture board, you don't read? It's a backlight LED driver board. Are marked on pcb "Fxxx"

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Old 11-25-2017, 10:42 AM   #8
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Default Re: NEC MultiSync V552 power on and off (E-Waste Dumpster Diving)

here are the 3 fuses.
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Old 11-25-2017, 11:16 AM   #9
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Default Re: NEC MultiSync V552 power on and off (E-Waste Dumpster Diving)

Is it possible to test them whit a multimeter?
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Old 11-25-2017, 12:01 PM   #10
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Default Re: NEC MultiSync V552 power on and off (E-Waste Dumpster Diving)

Yes, sure... use continuity without current in circuit, or voltmeter with current, (volt on both pins)..
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Old 11-26-2017, 05:32 AM   #11
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Default Re: NEC MultiSync V552 power on and off (E-Waste Dumpster Diving)

It's probably the backlight if it's LED backlit, looks like that's an LED driver.
https://www.badcaps.net/forum/attach...0&d=1511605764

You want to check for (I think) 24V input to that board

You want to check for the VH1, VH2 pins on , these are the high voltage outputs. I'd expect at least 100V. These will go to the Anodes (+) of the LED strips.

You want to check each of the VFB pins. Any that measure more than a few volts are likely to be at fault. These will go to the Cathodes (-) of the LED strips.

It's like christmas lights. If one LED goes bad the whole set dies. Bad design - but hey what can you do...

If you see high voltage on the outputs, but there are some VFBx-x that measure high, then you have open circuit LEDs in the panel. So you have the fun task of stripping the panel to find and replace the LEDs.

You might find that the driver board is dead though if the VH1,VH2 are missing or low.

You might find everything is ok and the main board is shutting down for some other reason.

If you can find the model number of the LCD panel then you will likely be able to find the pin out for that connector. Though it is probably similar to LCD CCFL backlit TVs and there is an error output pin which will indicate the fault and cause the set to shut down with the "2" code.
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Last edited by tom66; 11-26-2017 at 05:36 AM..
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Old 08-29-2019, 01:12 PM   #12
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Default Re: NEC MultiSync V552 power on and off (E-Waste Dumpster Diving)

Any update on this issue? I have the exact same problem with the exact same model and i cant figure it out...
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Old 01-24-2021, 12:27 AM   #13
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Default Re: NEC MultiSync V552 power on and off (E-Waste Dumpster Diving)

Hello guys, i got the service manual, i'll upload it have fun!
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Old 05-12-2021, 04:06 AM   #14
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Default Re: NEC MultiSync V552 power on and off (E-Waste Dumpster Diving)

I've got the same problem here.

+110V backlight is good.
+24V line is steady and good
+12V line steady and good
+5V line steady and good

Fused are all okay

Monitor boots up, shows source (HDMI) for a second, then flashes green, then shuts down and this cycle continues for 10-15 seconds. After that the main relay is disconnected and red light flashes 2x and repeats this "error code"

The service manual does not really provide more information to me...

I tried disconnecting the ERR_OUT pin to the main board, but no success.

I have no idea what this can be, any suggestions?
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Old 05-12-2021, 07:40 AM   #15
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Default Re: NEC MultiSync V552 power on and off (E-Waste Dumpster Diving)

It could well be a backlight inverter board problem or even a led problem.

"Fuses are all OK." These are the 3 that are on the inverter board and hecked out OK?
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Old 05-12-2021, 11:13 AM   #16
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Default Re: NEC MultiSync V552 power on and off (E-Waste Dumpster Diving)

There is an ERR pin that runs from the backlight module to the powerboard, where it is directly connected through to the mainboard.

What seems to be the problem -> backlight module shuts down after 10 min and reports an error -> mainboard resets the powerboard and this cycle happens over and over again.

I monitored the 24V to the backlight module during this "shutdown" -> no change, no dips nothing. The output voltage from the backlight module just suddenly drops from 117V -> 24V (the boards VCC).

I cut the ERR wire running to the mainboard (logic) and grounded it.
The mainboard and powersupply now are running continuously, but after 10 min the backlight stops working. The TV remains operational and reports no errors (apart from the screen being black due to no backlight)

For some reason when the PWM input op the backlight module gets connected to the mainboard PWM output to control the brightness, the backlight module does not even try to start.

You can manually restart the backlight module by grounding and releasing the VBLON pin.

Tried upgrading the capacitors of the backlight module, with no luck. By adding more capacitance the module cuts out quicker then with the standard capacitors.

Now I'm quite certain the issue lies in the backlight module, I ordered a new one from aliexpress for 10 dollars...

https://nl.aliexpress.com/item/32826821184.html

Lets hope this one works, otherwise there might be some kind of problem with the backlight?

It gets warm, but not hot, and the screen works perfectly for 10 min, so don't suspect the led backlight to have an issue.

Will let you know
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Old 05-13-2021, 03:51 AM   #17
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Default Re: NEC MultiSync V552 power on and off (E-Waste Dumpster Diving)

Okay after doing some more measurements to check what @tom66 said;

All of the VFBX pins (the negative side of the leds) are measuring 0.5~ish V.
Except 2, VFB2-2 and VFB2-3. VFB2-2 measures 6.2V when the TV is cold and 6.3 when its gets warm. The VFB2-3 pin start around 9.1V and rises until 9.2V when the TV gets warm.

At VFB2-3 = 9.23~V the backlight driver shuts down and the backlight stops working.

Is this due to failing backlight LED's? Would this mean that I need to replace 2 strings?

Do you think its worth it (2 strings cost approx. 10 EU)?

Last edited by chagay; 05-13-2021 at 04:02 AM..
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Old 05-16-2021, 11:02 AM   #18
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Default Re: NEC MultiSync V552 power on and off (E-Waste Dumpster Diving)

I "fixed" it by connecting the VFB2-2 and VFB2-3 to VFB2-1.
This way the backlight driver does not "see" the rising voltage across the led strips 2 and 3 and keeps working.

Only downside is that you can now visually see that in the upper right corner the backlight is a little dimmer.
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