Schematics from NEC LCD1830 inverter: ALPS UHP061104

schematic inverter lcd

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..

nec multisync lcd 1830 no image fix

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.

lcd1830 inverter

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.

inverter hiu-391c

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.

lcd+inverter+with+lm339

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...

lcd iverter schematic

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...

multisync lcd 1830

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.

multisync lcd 1830, take apart

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

nec 1830

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

inverter board tft monitor schematic

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

laptop inverter board schematic

Hello,

I increase R28 from 680 Ohm to 1KOhm, because of the Information from wulw.
He change R28 and C15 and the TFT ist running.
I think, that R18 is to limit the current through die Diode.

Now, i can't meassure, because me measurement is dead.

Can you give me a tip, how I can repair die TFT, that it run over 15 seconds?

I'm happy about any answer.

Thanks

Marcel

nec lcd 2010x backlight board schematic

Marcel, from your postings, it looks like you are not having a lot of knowledge of electronics. If that is the case, it's hard for me to explain to you how the circuit exactly works, in order for you to understand it. Besides I feel you are wasting my and that of others their time. From the things you experimented with, it looks more like you did some random testing, instead of first understanding the circuit structured. Also in your case, working measuring equipment is a must if you want to 'get your hands dirty'. How can someone understand what is going on, if you can't measure anything? How should the community know then what's your problem?

Anyway, from the schematic, I see comparator U1C and U1D, which play the essential role in measuring lamp current. Initially, when Q12 is triggered via a positive puls across C26, Q3, Q4b and Q4a will be triggered as well. With this, the comparator LM339 itself will be powered and being able to compare voltages. The voltages of the 'Measure lamp current' circuit (see at the bottom of the schematic) are compared against a voltage which is offered at the negative input, pin 8 and 10 of U1C and U1D. Via R10, zener D4 regulates the voltage at 6.2 V, which is divided with R17 and R18, which gives a voltage of: 6.2*(100k/(100k+270k))=6.2*10/37=62/37=1.7V. For the comparators in order to remain powered, it makes sense, the output of U1C and U1D, pin 13 and 14 must remain 'high' (open collector output!). With that R34 will guarantee through Q13 that this condition will stay. However, as soon as the output of U1C and U1D becomes low, the comparators will be switched of, via Q13 and Q3.

The 'Measure lamp current' circuit should provide a voltage on the comparator positive input to be at least MORE than the previously calculated 1.8 volt. You can see at R30, I wrote 0.27v, which must be incorrect. It means that the voltage at the anode of D12a should be 0.27v+0.7v. Since 0.97v (+input)<1.8v (-input), comparators U1C and U1D will shut down themselves via Q13.

The 'Measure lamp current' circuit has only one importance, that is to protect the transformer of building up high voltage, when lamps are open. In that situation, the voltage across R30, R29, R.. and R.. (I did not draw that part of the schematic, as it is identical to that of CN5 and CN4) will get lower, because the lamps are contributing LESS to the voltage across R28, R25, etc.
One thing for sure is that the voltage across R28 etc. should be higher than 1.7v (Due to D12a/b and D11b,D9b). With that the voltage across R30, R29, R.. and R.. will raise as well. Basically the voltage across R28, R25 etc. can be measured as well at the positive inputs of the comparator. So if you measure in lamp 'warm condition' 1.7v or less across R28, R25, R.. and R.., or pins 9 and 11 of the comparators, you know the problem has to do with either the CCFL's or as well something with the royer-oscillator.

Unfortunately I can't supply you with accurate measurements which voltages you should expect in normal 'warm' operation. I've seen that other users here mentioned 1.55 volt at pin 8 and 10 of U1C/D, which is a bit different than the 1.7v I mentioned. I've read at a lot of sources, what lamp currents can be expected. Some sources mention 4 mA. If these CCFL lamps are also in this inverter, the voltage across R28, R25, etc. will be roughly 2.5v.

Regards, Marc

ccfl backlight for nec lcd 1830

Hi Marc,

thanks for your very good posting. It's very good. Now I decrease R18, so the voltage to compare ist lower than 0,97V which is at the diode.
The monitor run and doesn't shut down, but the backlights glimmer. Can you explain why?
Is there anything dead?


Regrads Marcel

manual nec lcd1830

My first post & I wanted to say THANKS for the info in this thread. My LCD1830 died and when I got it apart, I figured it had to be the inverter board (screen completely dark). Did a google on the board part number, ended up here, touched up the solder on those 4 resistors and ... ta da !! It works again. Thanks.

nec lcd 1830 repair

Why can't I find those Rs from the inverter schema?

I got similar problem on Acer AL1914bm LCD monitor. Changed the four ccfls. Still has the same problem. Monitor come on for one or two seconds then gone. Power light always green.

Can't find the schematic for AL1914bm any where :-(

schematic inverterboard 1830

These resistors are part of the royer-oscillator, and can be found between Q8 and Q9, marked as R1112. To enable larger power dissipation, for each branch, two resistors of 270 Ohm each are connected in series. You are right it's not drawn in the schematic, but if you understand how the circuit works, I'd say it is not that hard to find them though.

backlight inverter schematics

Hi all I was having trouble with a nec 1712 lcd monitor it stays on for about half a second then the backlight turns off and I was wandering if any one had the schematics so I could try and fix.

laptop lcd inverter schematics

Does anyone know the value of F1 on the inverter board. I have Q8 and Q9 blown plus F1 and I can't find the value of it.

nec uhp061104 c11,c12

I had the same issue with my NEC 1830 monitor working for 2 to 10 seconds (green light on) and then blinking off (green light still on). Don't know if these values will help others - but here's what worked for me: I swapped R18 with a 4.7K resistor, and I swapped C16 with a 1000uf cap (the higher the value, the less flickering you get). This has kept the U1C and U1D comparator from switching off. (Just re-flowing the solder joints on R11 thru R14 and the other caps mentioned in previous posts didn't work for me.)

Good luck!

backlight schematic

Good morrow to all,
Please can someone specify what Voltage the F2-F5 1.25A Fuses are? I know of an electronics manufacturer I would approach instead of buying F4 and F5 on a reel of 5000. Maybe as I worked there once they might spare them or order them for me. They look like 0402 1.25A but that's as far as I got.