NEC Multisync 1830 XtraView - Dead inverter

[EGuevarae]

Looking around the forums for an answer to my problem, I found none, so here I go.
I got a NEC 1830 from eBay, stated that powered on but black screen. I bought it just because $25.00 shipped for a 18" is not that much and would be a very didactic experience. Well, my didactic experience is quite bad so far.

I found a thread in another forum regarding this specific monitor. Then, on another page, I found references of the same monitor, same problem (inverter). It is signed "Cheers, Wizard", so maybe it is the same Wizard in this forum (hopefully, so he can give me some advice).

So far, I've tried the resoldering of R11~R14, and C11 & C12. Measuring the Rs in question , all but R12 measure 268~272 (R12 measures 202Ohms).
If I check Q8 & Q9, I get continuity on all three pins (shorted?). Then if I measure resistance on C11 & C12, I get 0ohms (shorted also?).
If I turn on the monitor and turn on the lamps with my lamp tester, the monitor works OK (except maybe the issue with the PSU, that humms when in standby/no signal)
Any advice (besides throwing the inverter to the dumpster) would be greatly appreciated.

--- I posted pics of the whole inverter, but in sections, for it to be clearer ---

[Wizard]

Re: NEC Multisync 1830 XtraView - Dead inverter

This is exact LCD monitor I fixed by using a samsung inverter board from a 17"-19" and wired it in. The lamp plugs right in. Takes some work to mount the board to the metal back and yet can fit metal box on.

Performance is ok for this monitor. Not exactly a gamer's and with no DVI, forces you to use native resolution for sharpness.

Cheers, Wizard

[EGuevarae]

Re: NEC Multisync 1830 XtraView - Dead inverter

So, in your opinion, it is better to find a replacement than mess with this one? I've done that kind of adaptation before. I just wanted to know if it was possible (due to my limited electronics knowledge) to fix the original instead of going that route. I guess this will be the only solution to this case and the Totevision 18" one.
And thanks for answering.

[Toasty]

Re: NEC Multisync 1830 XtraView - Dead inverter

Did a quick look about and found this schematic. Perhaps it can help?

Schematics from NEC LCD1830 inverter: ALPS UHP061104

Toast

[EGuevarae]

Re: NEC Multisync 1830 XtraView - Dead inverter

Did a quick look about and found this schematic. Perhaps it can help?

Schematics from NEC LCD1830 inverter: ALPS UHP061104

Toast

I got that already (even printed. First schematic I ever print ....). It would be really useful if I can traduce it to plain English (understand it), or even better, to Spanish! , but I really can't do mush, as my electronics knowledge is rather limited. I resoldered (the so called reflow) the indicated resistances, and caps. I still have a dead inverter. I guess it has something to do with the two shorted caps I found and the shorted Qs, but I have no way to test further as I don't have the Qs, and the value for the shorted caps is not available, so replacement is not an option.... so bad , as I really like the monitor.

[Wizard]

Re: NEC Multisync 1830 XtraView - Dead inverter

Reason this particular failed is the transformer shorting out and pumping low output in one of transformers and shuts down.

I use scope with probe 10x set and volt/div .1 and around 20uS sweep for sine wave. If one transformer is low amptitude than other then is busted. I don't have to probe directly, I lay side of the probe against the ferrite core where halves meet. Works well on flyback and SMPS transformers since I can't hear very high frequencies so this scope is what I visiually check.

Cheers, Wizard

[EGuevarae]

Re: NEC Multisync 1830 XtraView - Dead inverter

Do you think that this inverter can be a suitable solution, or it has to be one from a bigger LCd, let's say 17"?

[Toasty]

Re: NEC Multisync 1830 XtraView - Dead inverter

The most likely reason that the transistors(Q's) and caps are reading 0 (zero) ohms is that they are across the transformer coils. Tough to short those caps as they (from what I've read) are the ceramic chip type and in the in the picofarad range. (1uf = 1,000,000pF)

Also, try reversing the probes of your ohmmeter when you test a suspected component. Many meters present enough voltage/current when testing on the low ohms setting to forward bias (turn on) diodes and transistors. You get a reading one way, but when you reverse the probes, you get nothing or a different reading than the first one.

Are the fuses good?

If you power it up, does one transformer get warm and the other stays cold?

Toast

[Toasty]

Re: NEC Multisync 1830 XtraView - Dead inverter

Lot of 5 dead ones for $20.50 with shipping. Make one maybe, or fix one?

Ebay # 390024509540

[EGuevarae]

Re: NEC Multisync 1830 XtraView - Dead inverter

Lot of 5 dead ones for $20.50 with shipping. Make one maybe, or fix one?

Ebay # 390024509540

That's how I found the thread where you got the schematic.
This guy posted a ton of things he/she has already done to that inverters, so I don't' think that (at least me) could pull one working out.
As for the transformers, let me reassemble it and test. And I checked with the probes on both ways. But re checking does not hurt.

Also, can someone tell me why my signature sometimes shows and sometimes does not?

[Wizard]

Re: NEC Multisync 1830 XtraView - Dead inverter

The one you found on first ebay link is for 15" LCD but could be great on second ebay if you can find two good transformers from bunch of inverters but why the effort and they had failure rate? Too short tube length (they are determined by starting and running voltage. you want a driver board in that range between 17" and 19". This NEC is odd 18" size but even a 17" inverter works and reason I used samsung is I can buy new because we're authorized shop for samsung.

Cheers, Wizard

[EGuevarae]

Re: NEC Multisync 1830 XtraView - Dead inverter

I was using a VE500 inverter on the ToteVision (18" also), but only 2 of the 4 CCFLs were working, and I wanted to light the 4 ... So in the long run it will mean trouble?

[Wizard]

Re: NEC Multisync 1830 XtraView - Dead inverter

Are you SURE the CCFLs are the problem as it is impossible to tell without scope due to very high frequency (over 100KHz or more and at very low mA, only 3 to 6mA per CCFL depending.) also to see if transformers are outputting strong enough or shorted? (waveforms tell you lot by comparing to good transformer vs bad or something else.

And yes, it is a problem to run unloaded inverter or high voltage transformers because unloaded condition the output voltage climb so high and arc/burn thorugh transformer secondary HV windings.

Also not good idea to use underrated inverter made for shorter length CCFL or drive more CCFLs instead of designed for can burn out the transformer delicate secondary windings.

Cheers, Wizard

[EGuevarae]

Re: NEC Multisync 1830 XtraView - Dead inverter

Are you SURE the CCFLs are the problem as it is impossible to tell without scope due to very high frequency (over 100KHz or more and at very low mA, only 3 to 6mA per CCFL depending.) also to see if transformers are outputting strong enough or shorted? (waveforms tell you lot by comparing to good transformer vs bad or something else.

And yes, it is a problem to run unloaded inverter or high voltage transformers because unloaded condition the output voltage climb so high and arc/burn thorugh transformer secondary HV windings.

Also not good idea to use underrated inverter made for shorter length CCFL or drive more CCFLs instead of designed for can burn out the transformer delicate secondary windings.

Cheers, Wizard

If you are referring to "only 2 out of the 4 CCFLs", the inverter I adapted had only two outputs, that's why I wanted to fix the original, 4 outputs one.

And as for the scope, I barely have a pen soldering iron....

[Wizard]

Re: NEC Multisync 1830 XtraView - Dead inverter

Ahh!

That is ok all you get is a dimmer LCD with only 2 CCFL lit.

Up to 20" usually are 4 CCFLs, The inverter need to be 4 CCFL outputs (usually two transformers or four, but 17"-19" inverters can drive this kind of length of CCFL like yours.

Cheers, Wizard

[EGuevarae]

Re: NEC Multisync 1830 XtraView - Dead inverter

Ahh!

That is ok all you get is a dimmer LCD with only 2 CCFL lit.

Up to 20" usually are 4 CCFLs, The inverter need to be 4 CCFL outputs (usually two transformers or four, but 17"-19" inverters can drive this kind of length of CCFL like yours.

Cheers, Wizard

For the ones I've seen, it goes like this :
<14" : 1
14~16 : 2 (yes, I've seen a 16 one .... strange ...)
17~19 : 4
20~22 : either 4 or 6

I haven't seen bigger than 22", but I remember an eBay listing of an inverter with 8 outputs.

And yes, Screem was dimmer with just two CCFLs, but it was OK, I just wanted it to be with the four lamps, but, anyway .... I guess I'll end up with two 18" with "foreign" inverters and maybe two lamps lit only ...

And why my signature is not showing? ([ ] Show your signature is checked, by the way ...)

[Toasty]

Re: NEC Multisync 1830 XtraView - Dead inverter

...guy posted a ton of things he/she has already done to that inverters...

No, he's saying that he doesn't know how to fix them, but somebody might.

He is quoting from the website about the problems, under the red lettering "Information on Web", not that he tried to fix them and failed.

All I'm saying is that you may get all the parts to fix yours from the 5 that you'll get from him. Odds of all 10 transformers being bad...??? You might get one or 2 of those boards that just need the re-flow work done.

Re: signature missing - Best to contact a moderator like willawake or the admin Topcat by PM or post it up on the Site Suggestions thread.

Cheers!
Toast

[PCBONEZ]

Re: NEC Multisync 1830 XtraView - Dead inverter

Re: signature missing -
The signature here sort of comes and goes when it wants to.

[EGuevarae]

Re: NEC Multisync 1830 XtraView - Dead inverter

Re: signature missing -
The signature here sort of comes and goes when it wants to.

[EGuevarae]

Re: NEC Multisync 1830 XtraView - Dead inverter

No, he's saying that he doesn't know how to fix them, but somebody might.

He is quoting from the website about the problems, under the red lettering "Information on Web", not that he tried to fix them and failed.

All I'm saying is that you may get all the parts to fix yours from the 5 that you'll get from him. Odds of all 10 transformers being bad...??? You might get one or 2 of those boards that just need the re-flow work done.

Re: signature missing - Best to contact a moderator like willawake or the admin Topcat by PM or post it up on the Site Suggestions thread.

Cheers!
Toast

Ohh. Let me contact him. Maybe he's a nice guy, and will answer some questions. Lemme see my notes ......I think I've contacted him in the past.