Schematics from NEC LCD1830 inverter: ALPS UHP061104

(pdf)alps uhp061104

Similar to mrzilza's post reply above I found on the invertor board HIU-319C all fuses F2, F3, F4 and F4 broken and transistors Q5 and/or Q6 shorted emitter to collector. This board drives 4 lamps but it hosts 8 ferrite trafos, with every second trafo connected in parallel to the previous one. Each trafo pair is driven by a pair of two FMMT619 transistors. Moreover, it seems that all these switchers are somehow syncronised by means of secondary windings in the transformes.

I guess that if Q5, Q6 gone short-circuit then the oscillation of all other transistor pairs where stopped and this is the reason why all fuses blow up.

Has somebody a diagram for this invertor board? Or maybe had the same problem? I would proceed simple by replacing Q5/Q6 and the fuses ... but prior experince may help to avoid further pitfalls.

hiu-391c schematic

Hi all

I have the NEC LCD1830 lcd backlight shutdown problem with green power led staying on and I stumbled upon this thread which is very informative thank you

But I'm no electronic tech and weary to buy a new inverter board incase that wouldn't fix the problem. One thing though happened last evening as I opened the monitor to get familiar with the inside. I disconnected the inverter board to further inspect it visualy, didn't seem to have bad soldering in eye sight, though when I re-assembled the monitor together, to my surprise it worked and displayed throughout the bootup up to the XP welcome screen then finaly to shut down as expected.

What could that mean?

Thanks

P.S. all connections have been checked internaly and Monitor To PC incase something was loose, but no, everything shown to be tight.

alps inverter

Hello, thanks very much for the previous posts,
I have a NEC 2010x with the same backlight-turns-off-after-a-minute-problem.
I tried to compare & understand the inverter-board-circuit ,but
it's a little bit different!
Has someone any schematics or tips for this LCD-type NEC 2010x
Multisync, please then post it!
Bye & good luck!!

laptop backlight inverter schematic diagram

Hello again, here is the solution for the backlight flickering of the NEC 2010x MultiSync LCD-monitor:
On the power-board there is a relay (black rectangular box located just a few cm from the AC 220V input jack, with the number G3M-203P-xxx on it)
Now go ahead, switch on the monitor and when the lights go out give it a short sharp snip with a screwdriver's end, for example.
If the light comes back be happy- you have found the solution!

Greetings & good weldings!!

nec 2010x-t connections

I had the same issue with my inverter. R11 to R14 appeared to be soldered ok, but when I soldered one side, the entire resistor became loose, meaning that there was a cold solder.
Thank you for that tip !

ccfl inverter schematic

w_m0zart said:

... R11 thru R14 were badly welded. I hope it helps someone.
w_m0zart

Click to expand...

Wow - this sure helped me. I did a google for the model number, found your article, and checked the resistors carefully with a microscope - hairline cracks in the solder joints. I re-soldered and got my friend's monitor back again.

Thanks a million!!

alps uhp 061104

i got one off eBay, it arrived in like new condition, when i connected it up it operated just like above. nothing on the screen what so ever. i opened it up and got down to the boards. i connected all the cables up again and turned it on. after a few minutes i felt the power board and the memory, processor board and both were warm (have power going thru them) the back lite board was cold as ice. i reheated the solider connections on r11 thru r14 and also c11 and c12 and reconnected everything back and it came right on. this method works for a few reasons. all three boards were built by different company's the power and processor boards are top knotch built by Mitsubishi and LG. the back lite board is not that great a part (really cheaply assembled) most likely by someones wife at home lol. when they connected all the circuits on this board most were cold soldered (done too fast to be right) and when you reheat them up, well i think you get the picture or your monitor will. i figured all this out with the help of the people on this forum. i am not a electronics repair man. just a tattoo artist that wanted his new monitor to work. a regular solider iron with a filed sharp tip is all you need and a digital camera to take pictures of it as you take it apart (to help you remember how it was connected when reassembling) the whole gig took 6 hours including dinner. i hope this helps someone else and thank you ALL very much for posting all this different information. cliff at zebra tattooz.

Thank you for your help in creating the schematics. However d3a and b do not connect to V++. On my board, they connect as feedback from T1 pin 3 (T2 pin 3). This voltage is fed back into the comparators to prevent the comparators from making the display too bright. I had the same problem of poor solder on R11-14 as well (cracked underneath pad) and re-soldered them. I am waiting for two samples on the Zetex ZXTN25015DFHTA, but I'm sure it will work OK. You can short c26 to see if the 339 gets 12v. Whenever you repair something electronic you're trying to find what's broke! NOT modify the circuit. It will work fine if you replace the defective part or find the solder break. As a CCFL (cold cathode fluorescent lamp) ages it becomes ionized at the ends no different than an overhead fluorescent lamp and thus harder to drive with the same current level. If the transistors are aged, their performance has been degraded over time by heat and switching cycles. Naturally they might runaway thermally and short circuit. Which is what I discovered in my monitor board. If you get away with just R11-14 re-soldered you're lucky!

Anyone know what the value of Q1 is on the NEC1830 inverter board? It only says 5102 on the useful schematic and on the 8pin chip. The chip also has the letters 'OM' I believe. When I searched on line for it I couldn't find anything. Is Q1 an n-channel or p-channel? Is there an equivalent part I could use? The schematic is drawn showing a p-channel but should it be an n-channel since there is only positive voltage at the gate unless I have my logic reverse?
Thanks for your help.:|

I have an 1830 with a all black display. The inverter seems to be at fault. First problem was one side of R11 unsoldered. I should have stopped there but I went on to replaced Q8 and Q9. I think I blew up one with improper handling and static discharge. Fuse F1 is now open. I would like to try again to replace Q8 and Q9. Does anyone now the current rating of fuse F1?
I would appreciate any comments.
Best regards,
Ted
P.S. How about the part number and manufacture for Q1

Awesome! I just picked one of these up for $15, no back-light. R13 had a bad solder, poked at it and the light flickered on. Thanks for sharing your wisdom!!

Re: nec lcd 2010x backlight board schematic

Marc
do you know the part number for Q1 and F1 (or equivalent parts)

thanks IV

Re: nec lcd 2010x backlight board schematic

Hi all I to have a NEC LCD1830 monitor with the same problems of having no back lighting, after some research and going though this website have left me stumped as to tracing out the problem as the inverter has a full load on pin 7 (brightness / contrast line ) of about 9.6 volts when no input signal is received , then it drops to 0.7 volts when i attach a vga cable from my laptop to the monitor, so a signal is sent to turn the back-lighting on. have found that pin 5 (the lamp on/off ) is at 3.3 v not 3.7 v as the reversed engineered schematic by Marc Nijdam shows, by the way nice work marc. I have found out that (Q1 5102) is a IRF 7726 a -30V Single P-channel HexFET Power MOSFET in a Micro 8 Package a data sheet is avaliable from IRF7726 datasheet - -30V Single P-channel HexFET Power MOSFET in a Micro . Marc do you know where the pin7 on cn1 of your schematic leads to ? have traced it back to 6.g5 after cn202 on the main pwb schematic diagram page 7 of 8 of model lcd1830 then dissapers i can not locate it on eny of the other pages, have you worked out the brightness / contrast section as what ever govens that section may be responable for shutting off the backlighting by not feeding enough power to pin 7 on the inverter board.

Re: nec lcd 2010x backlight board schematic

Thanks everyone you have been a big help. I have 3 of these monitors with 2 of them not working. I put the working inverter board in the nonworking monitors and both came to life. I was able to repair one of the inverter boards by heating the solder but still have a problem with the last one. I don't need this monitor right now but at least I know what is wrong when I decide to repair it... well... I know what board is faulty at least.