NEC Multisync 1830 XtraView - Dead inverter

[EGuevarae]

Re: NEC Multisync 1830 XtraView - Dead inverter

Here's a picture of the area in question. If I put the probes as you said (well, in the places I THINK that are WHAT YOU SAID), I don't read any voltage drops.
I traced the tracks with a MM, and here's what I've found so far:

[Toasty]

Re: NEC Multisync 1830 XtraView - Dead inverter

Zero volts on all test points?

If zero volts across R1, then problem lies before Q5, as I suspected. The oscillator is not functioning. Check across the balance of the resistors. Polarity doesn't matter. Report back on any that show a voltage across them.

What voltage do you get (from ground) to pin 5 on IC U1 or across D4? -To the left of C5, above R4, right of R6. It has a band at left end and marking is C2. The banded end connects to U1 pin 5.

[EGuevarae]

Re: NEC Multisync 1830 XtraView - Dead inverter

Zero volts on all test points?

If zero volts across R1, then problem lies before Q5, as I suspected. The oscillator is not functioning. Check across the balance of the resistors. Polarity doesn't matter. Report back on any that show a voltage across them.

What voltage do you get (from ground) to pin 5 on IC U1 or across D4? -To the left of C5, above R4, right of R6. It has a band at left end and marking is C2. The banded end connects to U1 pin 5.

I just noticed a line in your signature - "I used to be paid to be a pain in the ass. Nowadays, I do it for FREE!". Great line.

And as for the readings, here they go:
(-) on Ground, and (+) on Pin #5 of U1 - Nothing (DMM just says 0.00 before I put the probe in the pin, and when I put it there, it shows -0.00, and return to 0.00 as soon as I remove the probe.
(-) on ground, (+) on D4 - Nothing.
I can't get V drops on anything.
That is as far as you asked. Now, here's something I found:
(-) to Pin 1 of input connector of the inverter (13v line), (+) on U1 Pin #5 : -12v
(+) to Pin 1 of input connector of the inverter (13v line), (1) on U1 Pin #5 :
12v (obviously, as probes are reversed and it is DC). But I get 12v this way too on D1,C11,C12,and output pins from the 5102 (5~8).

Have you heard "The more I learn the less I know"? Well. Now I am really confused.

[Wizard]

Re: NEC Multisync 1830 XtraView - Dead inverter

There are no R/C oscillator, this is network of drivers and load sensing. The many pins IC do this of PWM job and the series of resistors that burned or hot traces means transformer has bad winding. You need to make a ring tester and use a scope to see the waveform of the transformer. Shorted turn give very sharp short ring while good one have several decaying cycles.

The 8 pin IC is a transistor.

Cheers, Wizard

[EGuevarae]

Re: NEC Multisync 1830 XtraView - Dead inverter

There are no R/C oscillator, this is network of drivers and load sensing. The many pins IC do this of PWM job and the series of resistors that burned or hot traces means transformer has bad winding. You need to make a ring tester and use a scope to see the waveform of the transformer. Shorted turn give very sharp short ring while good one have several decaying cycles.

The 8 pin IC is a transistor.

Cheers, Wizard

I'm sorry, but what series of burned resistors?
And the T's had been taken apart and tested and they seem to be good. Are we talking of the same monitor here?

[Wizard]

Re: NEC Multisync 1830 XtraView - Dead inverter

Sorry. I was referring to other monitor about the series of resistors burnt up also this NEC monitor as well about the transformers.

Cheers, Wizard

[EGuevarae]

Re: NEC Multisync 1830 XtraView - Dead inverter

Sorry. I was referring to other monitor about the series of resistors burnt up also this NEC monitor as well about the transformers.

Cheers, Wizard

Ohh, I get it.
Well, now, seeing the progress of this specific case. What can you suggest? I have ordered a 4 output inverter already, but will love to fix this. Any Ideas?

[Wizard]

Re: NEC Multisync 1830 XtraView - Dead inverter

Ring the transformers as I advised. Only solution is rewind it but this is not worth the trouble and substitute the inverter supply board into these monitors like I did with several like this model and other models, not just Nec.

Cheers, Wizard

[Toasty]

Re: NEC Multisync 1830 XtraView - Dead inverter

>>But I get 12v this way too on D1,C11,C12,and output pins from the 5102 (5~8).<<

You're reading voltage (actually ground) up thru the E-B junctions of Q8, Q9 then thru R111, R112, then L1.

Are you getting power (read from ground) to pins 5 and/or 7 of the power connector (CN1) when you turn the monitor on by it's power button? The schem looks like it says 0 volts when off and 3.7 volts when on. This will be funny but sad if there is a problem with the input voltage to trigger the inverter on. Check the voltage on CN1 with it disconnected from inverter also.

[EGuevarae]

Re: NEC Multisync 1830 XtraView - Dead inverter

Are you getting power (read from ground) to pins 5 and/or 7 of the power connector (CN1) when you turn the monitor on by it's power button? The schem looks like it says 0 volts when off and 3.7 volts when on. This will be funny but sad if there is a problem with the input voltage to trigger the inverter on. Check the voltage on CN1 with it disconnected from inverter also.

I figured out the Pin assignments before I got the schematic. I had the readings in my notes, but anyway I re tested them and here's the data.
With CN1 Connected
1 - 13.27v
2 - 13.27v
3 - GND
4 - GND
5 - BL_ON : 3.3v w/VGA signal, 0v without it
6 - GND
7 - 9.13~9.26v ON but with no VGA Signal. 0.04V with input signal (Green LED)

With CN1 Disconnected:
All readings are the same, except for the 7th pin : it is dead without the inverter connected. Nothing gets in or out of there (on the VBoard side). Is a return or something?
Should I try connecting the inverter WITHOUT pin 7 cable attached?

[Toasty]

Re: NEC Multisync 1830 XtraView - Dead inverter

I think we have run into the unit tripping its overcurrent protection. There is a possible "fix" by increasing the value of 1 resistor and 1 cap. It's on the forums where you got the schematic back in the beginning. There's also a bit about checking the small black resistor-looking type fuse on the other board.

[EGuevarae]

Re: NEC Multisync 1830 XtraView - Dead inverter

I think we have run into the unit tripping its overcurrent protection. There is a possible "fix" by increasing the value of 1 resistor and 1 cap. It's on the forums where you got the schematic back in the beginning. There's also a bit about checking the small black resistor-looking type fuse on the other board.

OK, I'll give it a try, but will it last long (give me your best guess)?

And thanks for the help so far.

[Toasty]

Re: NEC Multisync 1830 XtraView - Dead inverter

Have you tried new tubes? It's been so long, I don't remember if you tried another converter on this unit's tubes or not. Or, if you tried tubes from another on this one.

How long will it last? Sorry, my crystal ball is cracked. DAMN CAT !!

[EGuevarae]

Re: NEC Multisync 1830 XtraView - Dead inverter

Have you tried new tubes? It's been so long, I don't remember if you tried another converter on this unit's tubes or not. Or, if you tried tubes from another on this one.

How long will it last? Sorry, my crystal ball is cracked. DAMN CAT !!

Maybe you have crap caps on the PSU of your crystal ball. Carefully open it up, AND GIVE ME THE BRAND AND SERIES of any cap you see.

Here's a picture of the LCD with the screen lighted by the two lower lamps using my super duper amazing out of this world $3.00 custom made lamp tester. I tested both pairs this way, and they lit evenly and beautifully, so it is the inverter that the problem lies within.

[EGuevarae]

Re: NEC Multisync 1830 XtraView - Dead inverter

Just to close this "case".
The original inverter never worked again. I will keep it because the transformers and other components are good.
The 4 CCFL generic inverter arrived, and I installed it using pins 1,5 & 6 (two blanks/unused between 5& 6), and it is working (10 hours so far). The bright works (the 13v input voltage varies as Brightness is manipulated in the control panel/menu of the LCD. It turns on & off when signal is applied/removed, etc.
Too bad I didn't fix the original. The monitor is working fine. The cost of the inverter was $15 USD shipped. Not bad for a 18" LCD.

[EGuevarae]

Re: NEC Multisync 1830 XtraView - Dead inverter

I just received another unit that besides being black instead of white/beige, has the same components and the same problem. The readings so far are just the same as the other one. THE SAME.
- Did I run into a common failure here? (The lady with more than 50 pieces damaged selling them on eBay on lots of 10 came to my mind ...)
- Should I apply the same "Generic medicine" as the last time?

[Wizard]

Re: NEC Multisync 1830 XtraView - Dead inverter

It is transformers. You will find that one is pumping less voltage than others.

I have suggested doing a ring test on these transformer to be sure.

Like testing a bell, it rings clean and clear while cracked or flawed one simply with very short ding/clank. Shorted transformer nearly doesn't ring at all.

Details on how to do this ring test is everywhere on google and bob parker did create flyback ringer tester as well.

Cheers, Wizard

[EGuevarae]

Re: NEC Multisync 1830 XtraView - Dead inverter

It is transformers. You will find that one is pumping less voltage than others.

I have suggested doing a ring test on these transformer to be sure.

Like testing a bell, it rings clean and clear while cracked or flawed one simply with very short ding/clank. Shorted transformer nearly doesn't ring at all.

Details on how to do this ring test is everywhere on google and bob parker did create flyback ringer tester as well.

Cheers, Wizard

Sounds interesting (I've done some research...), but it is too way out of my current scope/limited knowledge ....
What is killing me is that both inverters read the same, as if I was reading the same inverter twice. Maybe I'll buy the 5 units for $20.00 from eBay just to see if they have the same values, just to dissipate any doubt.

[Zir]

Re: NEC Multisync 1830 XtraView - Dead inverter

Hello everybody,
Quite new on this forum(s), but find VERY useful information so far.
Thanks a lot! Looks like my first post. Sorry for my poor English.
Just fixing one of NEC1830 wit problem EXACTLY the same as the author of this topic. My first one of this model. But still not giving up.
First of all, R11 to R13 if well soldered on the board should measure about 202 ohms each across individually,
because each one is in parallel with the other three in series.
Checking Q8 and Q9 in situ with a DMM showed OK as well as F1.
Then searched for defeat to enable comparators U1A to U1D working i.e. get at least power on its pin 3. Got it by making a short from U1 pin 8 (or 10) to GND.
Then I got backlight working but very dim. Trying to disconnect one by one CCFL, same results. Did a brute test by measuring T1/T2 primary current by placing an
A-meter across Q1 (S-D) an such a way completely disabling the PWM. Backlight worked with full brightness (I think) but not so long because Q8 and Q9 smoked and burned.
Didn't have the replacements, so somehow fit 2SC5707 and now the backlight works fine, but when the brightness control is not
set at maximum (100% duty cycle), the inverter oscillator(s) make audible noise. Not terribly bad, but I would like to get rid of that as well.
I suspect that is due to my transistors, so I ordered the originals (FMMT619) and hopefully get them in two days. Yesterday I checked output voltages with
a scope; all four lamps are getting about 2500 Vpp sine at 40 kHz. So I concluded that both transformers must be OK. Anybody has an idea what else can produce this noise when
the PWM is in the play.
I will post again if I make any progress. I hope this will also help someone, especially eguevarae.
Regards from Vancouver.

[Wizard]

Re: NEC Multisync 1830 XtraView - Dead inverter

Reason the transistors burned up is that one of transformers has shorted turn.

I can see the difference with the scope probe body against tranformer. The bad one has lower ampititude than other one.

Cheers, Wizard