Viewsonic VX2370Smh-LED - 1/3 of LED not working

[JarrodHook]

Hi team, hope you are all well.

I have a viewsonic monitor, model VX2370Smh-LED - a older unit, but I am fond of it and feel like this may be fixable.

1/3 of the LEDs on the light strip for the backlight do not work when powered on, or, rather, they flash on for a half a second and then cut off.

I've inspected the LED board and found that they all look ok, however running a continuity test with my multimeter shows some of them do not light up as 'steady' as some of the others in the strip, just a FYI, maybe a red herring?

Because all lights light up for a half second before 1/3 do not, I think it may be the mainboard.

As a FYI, there is a marker on the LED board at LED number 16 indicating LED (I mean, that makes sense since it's nothing but LEDS but anyway ) and there are clearly three segments on this board so that is why I am thinking it's a cap - especially how in the image of the board there are three caps near the power feed for the backlight..

I've had a search for schematics for the mainboard, but have had no luck.

The number on the mainboard is 0171-2271-4683

I've attached some photos as below to assist in any ideas. My gut feeling is a cap that is not able to hold its charge, however it has been more than a few years since I did this kind of thing so any help welcome!

Thank you in advance.

[R_J]

Re: Viewsonic VX2370Smh-LED - 1/3 of LED not working

The caps are not for each led line, they are likely for the boosted led voltage which is common to the 3 strings, the caps are not the problem, you likely have one bad led on the string that won't light. One end of the led string connects to the boosted voltage, the other end (return) is controlled by the ic. If one led is open/shorted in the string the ic will detect the wrong current draw and shut down.

[ZackN]

Re: Viewsonic VX2370Smh-LED - 1/3 of LED not working

I have a similar situation. Glad you posted this recently.

It would appear that the fix for this would to be either find and replace the ONE led that may be causing the variable current or to replace the LED assembly. Does anyone know of sources for this? I think it would be easier to replace the whole assembly, not sure what the cost vs time break down would be. Thanks OP for posting and thanks RJ for the potential diagnostic.

[JarrodHook]

Re: Viewsonic VX2370Smh-LED - 1/3 of LED not working

If one led is open/shorted in the string the ic will detect the wrong current draw and shut down.

RJ thank you for your response, I appreciate it. Thanks for the clarification about those caps too! You can see from my post count that I am very much a learner but have my moments (Tho they are few and far between according to my wife!)

As mentioned, I ran my multimeter over a few of the LED's in the section that is failing and I feel as if a few of them are not working, so when you say that if one LED is open or shorted, am I able to just patch a wire between them, taking the one LED out of the circuit?

Sorry for the basic question, 2020 has done a number on some of my skills!

I have a similar situation. Glad you posted this recently.

It would appear that the fix for this would to be either find and replace the ONE led that may be causing the variable current or to replace the LED assembly. Does anyone know of sources for this? I think it would be easier to replace the whole assembly, not sure what the cost vs time break down would be. Thanks OP for posting and thanks RJ for the potential diagnostic.

No problem ZackN, I always like to try and leave as much of a trail for those in the future if they come across this kind of board and post. As per my reply above, I'm hoping I can just remove the one faulty LED, but I shall wait for the advice from RJ.

Regardless, I did a google for the whole assembly very quickly before work but was unable to find it.

I shall post a update later on today, one of the joys of working from home is one can tinker during their 'lunch breaks'

[R_J]

Re: Viewsonic VX2370Smh-LED - 1/3 of LED not working

The led's in a string will draw a certain amount of current, and the ic is usually set up to monitor that current. shorting out one led will usually alter the current enough to trip the protection

[JarrodHook]

Re: Viewsonic VX2370Smh-LED - 1/3 of LED not working

Thanks again RJ - as I was waiting for your reply I just checked and three of them seem to be faulty, funny thing, after doing a really bad reflow on one of the LEDs when I power it on the entire board lights up and then goes black (normal for it's boot process)

Previously, it was not doing that, it would be 1/3 dead after a millisecond....so I wonder if my bodge resolder has helped, on this one LED, and the others just need a touch up too.

Failing that, I will try and see if I have any SMD LEDs in old devices I can nick.

Cross fingers!

[JarrodHook]

Re: Viewsonic VX2370Smh-LED - 1/3 of LED not working

A quick update, looking at the board it would be a pain to replace the LEDS, so on a whim I emailed Viewsonic support and service here in New Zealand and got a call a hour later from a chap in one of our other main cities.

I explained to him what I had done and what I had found, etc, and he is going to send me a replacement LED board for free, which is crazy!

I'll update this thread in future if I get it and if it all works, but FYI for anyone out there, it never hurts to ask politely!

Regards
Jarrod

[momaka]

Re: Viewsonic VX2370Smh-LED - 1/3 of LED not working

Sounds good, keep us posted what happens.

Regarding the LED strip that worked after you retouched / resoldered a few LEDs...
Some LEDs will get a die bond issue (typically due to being pushed to work too hard over a long time). Reheating can temporarily "revive" the LED for a while. But usually, the LED will fail in short order again. And furthermore if one LED failed because it was likely worked too hard, that means the other LEDs in the strip are probably not far behind and likely will fail too sometime soon.

So all in all, you're doing the right thing by replacing the entire LED strip board rather than messing about with replacing individual LEDs.

Of course, you can keep the old LED strip in case you encounter any projects in the future where you have to replace or use an LED. So if you have the "electronic hobbyist" in ya, you may find the old LED strip board useful for future projects.

And last but not least, those three bigger electrolytic caps on the main board by the "330" inductor appear to all be cheap brands. While they may not cause any issues anytime soon (or maybe never if the board runs cool and they are not over-worked), you could also try replacing them with quality Japanese brand caps if you intend to keep this monitor for a long time (and if you have the tools and time to do the soldering, of course.) Otherwise, you can just leave those caps as-is.

[JarrodHook]

Re: Viewsonic VX2370Smh-LED - 1/3 of LED not working

Thanks for the super informative post Momaka - I indeed now have a old LED strip in my 'pile of things' for future use if needed!

On Monday this week I got a box from Viewsonic Christchurch, NZ, sent for free, no cost for postage or the part!

Plugged the new LED board in, and it worked perfectly.

I emailed the chap in thanks of this and got this email back (whose name I quote in full below because I am super grateful to him)

"Hi Jarrod

Its my pleasure , great to hear the monitor is working and that you take the time and effort to get things working again, instead of throwing them away.

If you have any other electronic item that need parts or repairs we are here to help.
Have a great weekend

Regards
Pierre de Bliquy"

So - the moral here is that there are indeed good people left in the world (For those feeling down about the whole Covid thing, like me!) and that indeed, repairing things is awesome.

But hey, you all knew that, why else are you on these forums?

So, big big thanks to Viewsonic support Aus/NZ! I'll reassemble this weekend and post a final picture then.

[sam_sam_sam]

Re: Viewsonic VX2370Smh-LED - 1/3 of LED not working

I am really surprised that you got this kind-a response from the manufacturer but you are right there still good thing happening and there still good working people out there it is just hard to find it in this day and age

I have even had technical support personal have bent over backwards to to help me fix our machine but it is rare to find people that are willing to do this anymore