My Viewsonic VX924 monitor died!

[jfr1326]

Re: My Viewsonic VX924 monitor died!

What country do you live in? Shipping for USA customers is around $2.75 USD.

I live in the UK. Shipping for DigiKey, Mouser, RS etc etc.. are all a fixed minimum of 12GBP. If I knew of anybody shipping at a reasonable rate, I would buy from them.

[jetadm123]

Re: My Viewsonic VX924 monitor died!

Thanks PlainBill and Jetadm123. The transistors and poly caps arrived with the usual exorbitant postal costs from DigiKey. They are now soldered in and ........a lovely bright, colourful monitor. Thanks guys.

Congrats on the repair! Yeah, I'm grateful that I have access to digikey with low cost shipping.

[Perineum]

Re: My Viewsonic VX924 monitor died!

I have recapped the entire PSU and now the monitor turns on, but only for a second.

It turns on, then turns off about once a second, repeating. The MBR10100 tested fine when I pulled it out.

I have not touched the logic board yet but that is where I was about to head to.... I've read 3 or more threads on this monitor and I'm still not sure what the blinking green power LED means....

[pedro]

Re: My Viewsonic VX924 monitor died!

I have recapped the entire PSU and now the monitor turns on, but only for a second.

It turns on, then turns off about once a second, repeating. The MBR10100 tested fine when I pulled it out.

What brand/series of caps did you use in the recap?

I have not touched the logic board yet but that is where I was about to head to.... I've read 3 or more threads on this monitor and I'm still not sure what the blinking green power LED means....

Usually a power LED blinking about once a second is symptomatic of the SMPS attempting to start, failing, and repeating this pattern. Typical causes are faulty (or inappropriate) caps, faulty rectifiers, short on an output rail, etc.

As a first step, address the cap replacement questions - what you used, and whether you replaced ALL the electros (other than the biggie). Don't bother with the video board yet, until the PSU is cleared of suspicion.

[Perineum]

Re: My Viewsonic VX924 monitor died!

I replaced the 400v 100uF with a nichicon PT(M)

The (2) 25v 470uF caps by the MBR10100CT are UCC KZE

The (C21) location I put a 35v 330uF Rubycon MHE

Beside the largest cap I placed a nichicon 10uF 50v VZ(M)

Lastly, the cap near the 6 pin connector is another 35v 330uF Rubycon MHE

The values should all be fine or overkill now except I may have messed up and not used low ESR caps where I needed to....

Also, I went through the board and hopefully (maybe I missed a few?) touched up all the pins to make sure there wasn't a cold solder joint.

Thank you for your help

[Perineum]

Re: My Viewsonic VX924 monitor died!

Okay, I found https://www.badcaps.net/forum/showthread.php?t=2280

The nichicons and Rubycons I used aren't on that list.

I suppose that is my issue? Which caps are part of the SMPS circuit?

[PlainBill]

Re: My Viewsonic VX924 monitor died!

All except the big (100 uF, 450 volt) one. OK, technically it is, but it does not have to be a low ESR cap,

PlainBill

[Perineum]

Re: My Viewsonic VX924 monitor died!

The (C21) location I put a 35v 330uF Rubycon MHE
The cap near the 6 pin connector is another 35v 330uF Rubycon MHE
Beside the largest cap I placed a nichicon 10uF 50v VZ(M)

Ok, swapped out the 35v 330uF Rubycons for ZL's of the same values.
Then swapped the 50v 10uF Nichicon for a UCC KY of the same.

All caps report correct capacitance according to my Fluke 12, but I have no idea if the ESR is off (No ESR meter here)

The monitor's symptoms are slightly different now. The picture is there, but the backlight comes on.....

"grey to dull, suddenly bright, then off, then repeating about 4 seconds later" - according to the girlfriend.

[Perineum]

Re: My Viewsonic VX924 monitor died!

So what should my next step be?

I'm afraid that my soldering is much much better than my troubleshooting skills.

Should I be checking ESR on the replacement caps?

[alexanna]

Re: My Viewsonic VX924 monitor died!

So what should my next step be?

I'm afraid that my soldering is much much better than my troubleshooting skills.

Should I be checking ESR on the replacement caps?

Post some in focus photos of your power supply front and back,using managed attachments.
The blinking PLED could be caused by voltages coming and going, Maybe from an overload on the power supply causing it to start and stop.
Are there any voltages listed at the connector from the power supply to the logic board.
If they are printed on the board what are they and are they steady?

[Perineum]

Re: My Viewsonic VX924 monitor died!

Post some in focus photos of your power supply front and back,using managed attachments.

All the pictures are here: https://www.badcaps.net/forum/showpo...50&postcount=3

The blinking PLED could be caused by voltages coming and going, Maybe from an overload on the power supply causing it to start and stop.
Are there any voltages listed at the connector from the power supply to the logic board.
If they are printed on the board what are they and are they steady?

Sorry for the long delay, I've been working 12 - 15 hour shifts right now. I will measure voltages when I can (soon hopefully). However, I did score a 4.5 amp 12 volt power supply so I can try that as well.

[Perineum]

Re: My Viewsonic VX924 monitor died!

I would like to report that the 12 volts from the PSU is fluctuating.

I would guess that the logic board is OK as the image looks fine for the half second it is up on the screen.

Am I still looking at a capacitor problem?

[Perineum]

Re: My Viewsonic VX924 monitor died!

Using the DC adapter to give it power via the capacitor nearest the 6 pin connector resulted in the monitor turning on once and then not again.

When I removed the connector it resumed it's normal non-working behaviour.

I did not have the AC plugged in at the same time as the adapter. Is AC needed at the same time?

[bo2000]

Re: My Viewsonic VX924 monitor died!

Hi!
I found this thread with google.
Awesome board!

I got an old VX924 from work to play with.
The problem was: You can turn it on, it shows a picture for about 1 second, then it wents black. The green power LED stays on.
When you remove the VGA- (or DVI-) cable and put it back on, it also shows a picture for ~1s and turns black again.

Now I changed all the caps like described, but the problem is the same.
But I just noticed, that I forgot one cap. C320. Could that be the problem?

I also checked the polarity and the connection of the new caps.
The logic board gets 12V steady.

2 pictures of my board attached.

Thanks in advance for your help and greetings from Germany

[Jasgriff]

Re: My Viewsonic VX924 monitor died!

Hi Bo,

Welcome to the forum and great job on the clear pics.

Do you have a spare working CCFL that you can use to do a few tests?

[Jasgriff]

Re: My Viewsonic VX924 monitor died!

What have you done with the main filter Cap in the middle?

[bo2000]

Re: My Viewsonic VX924 monitor died!

Hi Bo,

Welcome to the forum and great job on the clear pics.

Do you have a spare working CCFL that you can use to do a few tests?

Thank you!

I don't have a CCFL but a multimeter if that helps.

What have you done with the main filter Cap in the middle?

Yeah, I know it looks odd, but I only got one of these:

and I had to extend the feet to get it connected to the board.

[notrash]

Re: My Viewsonic VX924 monitor died!

Hi,

Great board.
Good to see that i'm not the only one with this problem.

As described I replaced all the caps on the board. I also replaced the two parts mounted on the heatsinks.
But still... if i start my PC the screen looks normal for ~1s and then goes black (as described by bo2000).
The green power LED always stays on.

I tried to measure the voltages at the connector to the second board. One of the top pins shows 12V the other two ~0V...

Any solution for this problem yet?

Thanks,
Martin

[selldoor]

Re: My Viewsonic VX924 monitor died!

@Notrash - Do you see an image of what is on the pc when the screen goes black.
try with a flashlght

When you tried to test the voltages was it all connected up

[Scenic]

Re: My Viewsonic VX924 monitor died!

Check the 4 inverter transistors on the backside of the board (Q6, Q7, Q8, Q9) for shorts

My Belinea 101910 (which uses the same PSU board) died on me while using it a couple months back.
One of those transistors was shorted and actually had a hole in it. When you tried powering it up, the backlight would just flash for a bit less than a second (inverter shut down), but the monitor stayed on (green power LED)

Replacing all 4 of them and resoldering the inverter transformers should bring it back to life.

According to the Belinea Servicemanual (parts list on page 61, inverter on page 46), Q6-Q9 are 2A 50V NPN transistors in SOT-89 package, specifically 2SC4672 by Rohm.

Keyword for these dying POS inverters is "royer oscillator". Searching for that on here will bring up a metric f*ckton of BenQ and Dell LCD monitor threads.. all of them with more or less the same problem.