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w_m0zart
Joined: 21 Aug 2005
Posts: 16
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 02 Nov 2005 1:51 Schematics from NEC LCD1830 inverter: ALPS UHP061104 |
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Here is a reverse engineered drawing from an inverter for the background light from a NEC LCD1830 TFT.
Two transistors were broken: Q8 and Q9. Fuse had been blown and R11 thru R14 were badly welded.
I hope it helps someone.
w_m0zart
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edw
Joined: 13 Jan 2006
Posts: 1
Helped: 1
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| 13 Jan 2006 18:05 Re: Schematics from NEC LCD1830 inverter: ALPS UHP061104 |
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I started troubleshooting my NEC LCD 1830 do to the monitor flicker problem. The monitor when turn on will display image for couple of second then turn black. The monitor status led is still green. This will happen each time it is turn on. The symptom at appear to come from the inverter board. I've check it will oscilloscope
and the high voltage circuit is weak and intermittent. Your schematic of the inverter was very helpful in troubleshooting this problem.
Thank you.
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wulw
Joined: 20 Oct 2006
Posts: 1
Helped: 1
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| 21 Oct 2006 20:57 Re: Schematics from NEC LCD1830 inverter: ALPS UHP061104 |
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Hello w_m0zart!
Thank you very very much for this schematic. 
Symptom: Backlight flashes short after start and then shut down.
I've invested several hours:
power board
- checked out power supply capacitors
- fuse 25V / 2.5A
inverterboard
- replaced C11 and C12 = 180nF / 250V
- check fuse F1
When the monitor was warm > 25° - it works
Next day - dark screen.
replaced the whole inverter board --> the same 
Then I found your schematic:
CN1 / 7: 250 Hz square 8Vss = duty cycle for brightness
The protection circuit causes shut down the backlight.
Each lamp connector CN2 – CN5 has a feedback with a rectifier. The DC voltage is measured above C13, C22, C24 and C25 and should be about 5V.
The comparator U1C and U1D compare this voltage against 1.55V (Pin 8,10 – C16).
The feedback of CN5.2 ( C25) had only 1V in cold condition. So the backlight shut down.
Next try only with power OFF / ON.
I change the connector CN5 and CN4 and also CN2 an CN3 – oh, oh – this fault moves to C24.
Okay, the backlight has a little problem. This is okay, because it has plenty of hours on duty every working day the last five years.
Change R28 from 680Ohm to 1kOhm, and increase C16 from 1µF to 220µF
Now the backlight turns on for 10sec. ignoring the protection circuit.
Backlight warm up and turns to normal operation.
Attention: This modification is no general repairing method for the dark backlight.
You’ve carefully checkout the behaviour with an oscilloscope before your change the components. Check the power consumption on the 12V CN1 / 1 (1.2A @brightness=50%; 2.2A @ brightness= 100%).
In case of disabling the protection circuit even for 10 seconds you might destroy the power circuit or the high voltage inverter.
 This case: more or less weakness of the backlight bulb.
Good Luck!
Werner
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stanw
Joined: 06 Feb 2007
Posts: 1
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| 07 Feb 2007 2:38 Re: Schematics from NEC LCD1830 inverter: ALPS UHP061104 |
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| R11 - R14 badly welded. Resoldered and monitor works like new. Thanks!!!!
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dolphin42
Joined: 09 Apr 2007
Posts: 5
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| 09 Apr 2007 6:01 Re: Schematics from NEC LCD1830 inverter: ALPS UHP061104 |
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Oh my I've been looking for info on this inverter board for ages, I've got two of these monitors that both blow fuses. Can I assume that I should
1. replace bulbs and pico fuses - old bulbs set off the over current detection?
2. troubleshoot any remaining problems
And many thanks for sharing your work with us!!
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w_m0zart
Joined: 21 Aug 2005
Posts: 16
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| 14 Apr 2007 1:23 Re: Schematics from NEC LCD1830 inverter: ALPS UHP061104 |
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> 1. replace bulbs and pico fuses - old bulbs set off the over current detection?
yes this seems very likely possible.
> 2. troubleshoot any remaining problems
Please, be more precise in what you mean.
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dolphin42
Joined: 09 Apr 2007
Posts: 5
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| 14 Apr 2007 5:39 Re: Schematics from NEC LCD1830 inverter: ALPS UHP061104 |
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ahh well at the time I didn't know what problems remained 
however I have repaired the unit and the monitor lived happily ever after.
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dolphin42
Joined: 09 Apr 2007
Posts: 5
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| 15 Apr 2007 11:08 Re: Schematics from NEC LCD1830 inverter: ALPS UHP061104 |
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I suppose I should put in my 2 cents worth here, and share what I've learned.
I had an 1810 display, not an 1830 (the 1810 has *8* lamps and a rather lossy screen with a near 180 degree viewing angle, very nice especially considering how old it is) - but your schematic was still helpful in that the design was similar enough... I had two bad (shorted) transistors on one of the transformer psuedo multivibrator output circuits. on the 1810 they simply drive four series-parallel bulb circuits, they double up the output circuit (two sets of transistors and transformers) and then take one side of the output on each transformer and ground it. The other side, I'll call it the "high" side of the two transformers - is used to drive two bulbs in series.
but the basic circuit, even the drive transistors, are the same types. The protection circuit is similar but there is also a 5th "master" fuse feeding the "big powerdown fet" and smaller fuses at each of the 4 subsections.
I suppose sometime soon I should try to generate a schematic for this board, as I have another 1810(the DVI input version) waiting for the same repair treatment...
if you can release the orcad .sch file that would be a timesaver but either way - I figure there is a lot excellent monitors out there that can be saved from the trashpile (and shame on NEC for leaving the schematic for the inverter boards out of the service manuals!)
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w_m0zart
Joined: 21 Aug 2005
Posts: 16
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| 17 Apr 2007 15:39 Re: Schematics from NEC LCD1830 inverter: ALPS UHP061104 |
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Here is an Orcad formatted file.
It contains several NEC Multisync related (unfinished) schematics from the LCD 1810/1830.
The inverter board HIU-391C (Partially; from the LCD 1810, which I tried to repair, but the scaler IC had severe heating problems. Later on I bought another one. It had the same problem).
The inverter board ALPS UHP061104
Power supply PCB DC-DC Conv. PWB PWE-627
The Control PCB PWE-588
The Control PWB (This is only the PCB with front panel switches)
The PCB with the AD Converter and Scaler E46669-711V
Good luck.
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Guitarman
Joined: 25 Apr 2007
Posts: 1
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| 25 Apr 2007 18:48 Schematics from NEC LCD1830 inverter: ALPS UHP061104 |
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| I have an NEC LCD 2010X that is having the same issue, intermittent backlight flickering on and off. This is the second one I have had with this issue. The first one just plain stopped coming on (still had green led). I purchased a second one off of ebay that had good working backlights but cracked LCD screen I used all the guts from the ebay one and just the LCD screen from the flickering one to create a good working monitor. It is now starting to do the same thing. I am hoping that the inverter is close to the same so I can try the repairs listed here. Does anyone have any suggestions??
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dolphin42
Joined: 09 Apr 2007
Posts: 5
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| 25 Apr 2007 20:04 Re: Schematics from NEC LCD1830 inverter: ALPS UHP061104 |
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thanks. I have a "complete" service manual for the 1810 (but no backlight schematic!!!) and if anyone wants a copy of the pdf, please feel free to send me an email...
dolphin
strangeanimals
net
and I will provide you a set.
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Jaspaa
Joined: 09 Jan 2005
Posts: 12
Helped: 1
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| 26 Apr 2007 23:35 Re: Schematics from NEC LCD1830 inverter: ALPS UHP061104 |
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Thanks for the schematic, really helped making things clear..I wonder though, I blew the 5102 Fet, but I have NO idea about the replacement for it. Does anyone have any clue which device this is?
Thanks!
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mini-me
Joined: 11 May 2007
Posts: 3
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| 14 May 2007 19:48 Re: Schematics from NEC LCD1830 inverter: ALPS UHP061104 |
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| I am also working on the Nec 1830 model inverter. Q8 and Q9 still left to replace. Has anyone found a suitable replacement for this transistor (FMMT619) ?
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Jaspaa
Joined: 09 Jan 2005
Posts: 12
Helped: 1
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| 14 May 2007 22:05 Re: Schematics from NEC LCD1830 inverter: ALPS UHP061104 |
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| mini-me wrote: |
| I am also working on the Nec 1830 model inverter. Q8 and Q9 still left to replace. Has anyone found a suitable replacement for this transistor (FMMT619) ? |
I have used the ZXTN25015DFHTA from Zetex, which seems to be doing very well. It's stocked by digikey.
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tnap1979
Joined: 01 Jun 2007
Posts: 1
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| 01 Jun 2007 6:08 backlight inverter problem.. need major help and info.. |
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hey all, lookin for some tips here,
i have the same nec lcd1830 white monitor, and it has the failing backlight problem,
i turn on the lcd and the backlight goes dead after like 15 seconds, the lcd still works,
i put a white led flashlight up to the screen to verify and screen still works, just no backlight...
now im on a low budget, not alot of money to buy the new inverter board previously mentioned in this post, so im looking for the cheapest and quickest alternative fix,
any help and info would be great from anyone who has fixed this monitor in the past,
i know its not difficult to fix, i just need to know what to fix, as i dont have an oscilliscope or testing tools like that, all i have is a multimeter and a soldering pen, i have plenty of old mobo's and electronics i could pick parts off of, or even better i have a parts supplier 5 blocks away,
just need to know the stuff to pull and replace, or alternatives to replace the dead ones with
like i siad, desperate and low budget, any help is more then no help
thanx all
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mini-me
Joined: 11 May 2007
Posts: 3
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| 06 Jun 2007 17:52 Re: Schematics from NEC LCD1830 inverter: ALPS UHP061104 |
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| It sounds like it may be a connection problem. Inspect the inverter board for bad/cold solder connections, especially around the 4 resistors mentioned in an earlier post. use a fine tip soldering iron.
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kellys_eye
Joined: 18 Jul 2007
Posts: 1
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| 26 Jul 2007 23:19 Re: Schematics from NEC LCD1830 inverter: ALPS UHP061104 |
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some excellent and useful advice posted here - thanks to all who contributed.
I'm currently reverse engineering the HIU-391C pcb and hope to post the schematic shortly.
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googlehopf
Joined: 04 Sep 2007
Posts: 1
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| 06 Sep 2007 9:31 Re: Schematics from NEC LCD1830 inverter: ALPS UHP061104 |
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Many thanks to w_m0zart !
Great work to reverse engineer the inverter circuit! Without this I had not been able to repair the monitor.
I have got a defect LCD1830 the backlight off. With the schematic and the comments in this forum I find a way to get the backlight working.
At my LCD1830 the comperator shuts down after 175ms operation. Due to all 4 current feedbacks increase the voltage with the same gradient and the comperators reference voltage at pin 8/10 have also the same gradient, I guess the bulb tubs are aged. Changing C16 to about 5uF does not help, but with 220 uF the backlight is switching on.
With 100% brightness the inverter draws 2,7A at cold condition and 2,5 A at warm state.
The current feedback voltage is about 7 V at every of the 4 bulb tubes. (C25, C24, ...)
Are these values similar to these from the others in this forum? The protection circuit does not switch off at static operation, so I think the feedback current is ok.
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rsure
Joined: 30 Oct 2007
Posts: 1
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| 30 Oct 2007 15:11 Re: Schematics from NEC LCD1830 inverter: ALPS UHP061104 |
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Hello,
I also have an NEC lcd 1830.
After flickering of the screen it went black.
Now it stays black but the lite goes on green.
When i push the reset button i see very dark a small display.
i used it for many years and almost the hole day.
Is this the backlight or can it also be something else.
Is it worth repairing or should i look for a new one?
thanks in advance
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jorb
Joined: 18 Nov 2007
Posts: 1
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| 18 Nov 2007 7:55 Re: Schematics from NEC LCD1830 inverter: ALPS UHP061104 |
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| Thanks for the schematic! Problem found. R11 badly "welded" on one end causing intermittent operation. Seems to be common on these from the other posts I read
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eagledot
Joined: 14 Oct 2007
Posts: 3
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| 29 Nov 2007 8:43 Re: Schematics from NEC LCD1830 inverter: ALPS UHP061104 |
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| I have a 2x LCD1810 that have problems with the backlight unit, if anyone have the schematics (reverse engineered I assume). It would be very helpfull..
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cbstrak
Joined: 02 Dec 2007
Posts: 1
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| 04 Dec 2007 19:51 Re: Schematics from NEC LCD1830 inverter: ALPS UHP061104 |
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I purchased the multisync 1810 from Milwaukee craigslist and it has the same backlight problems as many people are having.
screw fixing the inverter! I am in the process of converting the backlight to an all LED backlight. But I'm doing this on a budget so I am using the LEDs from LED flashlights purchesed at Doller Tree stores.
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mattelhart
Joined: 16 Jan 2008
Posts: 1
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| 17 Jan 2008 0:28 Re: Schematics from NEC LCD1830 inverter: ALPS UHP061104 |
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| I'm experiencing the same issue with the backlight turning off after a couple seconds. I have verified that fuses F4 and F5 are blown. being that this is an old monitor and the bulbs are aged, would the best course of action be to replace the CCFL's and then the fuses to prevent the same issue from happening again? Or aren't the bulbs the likely source of the blown fuses? Or should I just up the size of the fuse to overcome the change in draw from the bulb? The bulbs seem to be about $11.99 each. That means over $100 with shipping. Not worth it on this old screen. Input is appreciated.
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emiliano1984
Joined: 29 Jan 2008
Posts: 1
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| 29 Jan 2008 8:05 Re: Schematics from NEC LCD1830 inverter: ALPS UHP061104 |
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Anybody has a guide on how to open these NEC LCD1830? I am trying to open one in order to replace the inverters but the plastic frame is just breaking all over the place.
Any help is much appreciated!
thanks.
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ilijaf
Joined: 18 Dec 2007
Posts: 1
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| 14 Feb 2008 10:00 Re: Schematics from NEC LCD1830 inverter: ALPS UHP061104 |
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In my case Q8 and Q9 and F1 were broken, i replace them and when i power on the monitor the transistors Q8 and Q9 again were broken.
Please anybody help me...
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barryfish
Joined: 17 Feb 2008
Posts: 1
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| 17 Feb 2008 14:48 Re: Schematics from NEC LCD1830 - OT: NEC 2080 |
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Help !
I have a 2080 that seems to have a 1/2-dead line supply. There are 2 power sections: +5 and some other voltage (assumed to be 12V) The Green led is on and does not respond to front panel button pushing.
There are 3 optos in the supply assumed to be 12V FB, 5V FB and 12V power control. The power opto is saturated on, but that section is not running.
I've applied an external 12V and less than 100ma is drawn. There is no life. Is the switched supply 12V (the caps are 25V)???
Any help, service info, schematics or educated guesses will be appriciated.
regards,
Barry
Added after 37 minutes:
My own question answered,
The supply is 18V I looked at the opto ckt. FB comes from a typical prog zener. The opto turns on at 18V
The monitor seems to be coming on... (it's face down, but I saw video at a corner that hanging off the bench..)
About 2.1 Amps at 18V.
Now for the supply diag...
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mrzilza
Joined: 27 Feb 2008
Posts: 1
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| 27 Feb 2008 11:43 Re: Schematics from NEC LCD1830 inverter: ALPS UHP061104 |
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i have been screwing around with 10 lcd 1810´s witch have the inverter board hiu-391c.
now i have found some really interesting problems. in 1 inverter board we have found that the q5 and q6 both where broken so we replaced them. now it still did not all work. so still looking around trying to figger out what is happening all. so oke here we go big step we took but the fuse f4 and f5 that where broken. well just take a soldering pen and overpass them. i know this is not supose to be done because the fuse is there to protect well i really dont care haha i just want to figger out how the damm thing works again after 3 days of work i think i am making some progress.
so to check how the q5 and q6 are broken you get your multi meter and put it in resistance now put both the pen´s on the 2 feets beside each other if your meter cant reach it its oke when you see that he gives a reading its broken.
well i hope that i can help some people with this.
and please no messages about o you may not do this with fuses or what ever i am trying to help thanks.
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Candyman
Joined: 04 Mar 2008
Posts: 1
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| 05 Mar 2008 0:08 Re: Schematics from NEC LCD1830 inverter: ALPS UHP061104 |
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Just putting in my work on my monitor for others to read and gain experience by.
Monitor: NEC Multisync LCD1830
Problem: No display - Nothing ever appears on the screen, and the backlight never goes on. LED Goes green then orange. Remains green when signal applied.
Opened the monitor up and checked it out (it had seen some action - A lot of brown heat marks on the plastic and occasionally on the circuit board).
Both Powerboard fuses OK - No dry-joints (bad welding  ) on this board.
Power level appearing on CN1 Pin1 backlight connector 13.8V.
Problem appears to be the Backlight Board UHP061104.
Tested transistors Q8 and Q9 OK. Examined Resistors R11 thru to R14. Looked ok, but had obviously been 'heated' at some stage - Re-soldered them anyway.
Examined capacitors C11 and C12. Looked OK, but re-soldered anyway.
Monitor now powers up and works - All I did was re-flow solder on R11 to R14, C11, and C12 - They didn't look like they needed it really.
Unsure if I have 100% fixed as the backlight has been 'shaking' now and again whilst I have been looking at it - I will replace C11 and C12 anyway, as they could be the issue I think 180nF / 250V - Thanks for the values.
Thank you to the members on this page who helped me out.
Chris
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marcel.hirsch
Joined: 10 Mar 2008
Posts: 3
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| 12 Mar 2008 22:29 Re: Schematics from NEC LCD1830 inverter: ALPS UHP061104 |
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Hello,
i have a little problem with my monitor.
At the top of this topic, there was a problem, that die monitor is on for about 15 seconds and then the backlights switch off.
Can anybody help me to find the problem.
I change R28 from 680 Ohm to 1K an C16 from 1µ to 220µ without a success.
I increase C16 up to 500µ but it isn't better then before!
I'm happy for any tip.
Bye Marcel
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w_m0zart
Joined: 21 Aug 2005
Posts: 16
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| 17 Mar 2008 0:56 Re: Schematics from NEC LCD1830 inverter: ALPS UHP061104 |
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Hi Marcel, I can't figure out why increasing R28 would be a solution. Please explain.
Also it would be good if you share with us some measurement results you have done so far.
Regards, Marc
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