My Viewsonic VX924 monitor died!

[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!

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?

[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.

[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!

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?

[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

[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 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....

[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.

[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.

[retiredcaps]

Re: My Viewsonic VX924 monitor died!

the usual exorbitant postal costs from DigiKey.

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

[jfr1326]

Re: My Viewsonic VX924 monitor died!

Bingo!!! A bad poly cap will cause the transistors to fail.

If I recall correctly, the Belinea 101910 service manual is available, and is an exact match for this monitor.

PlainBill

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.

[PlainBill]

Re: My Viewsonic VX924 monitor died!

http://bambooz.pytalhost.net/badcaps...nea_101910.rar

Vielen Dank.

PlainBill

[Scenic]

Re: My Viewsonic VX924 monitor died!

If I recall correctly, the Belinea 101910 service manual is available, and is an exact match for this monitor.

http://bambooz.pytalhost.net/badcaps...nea_101910.rar

[jfr1326]

Re: My Viewsonic VX924 monitor died!

If it's the orange cap, then it's a poly cap. Replace both as these have been known to fail.


Hopefully, this makes sense. The "154" is capacitor code for:

15 is the cap value followed by the multiplier (in this case 4 zeros) and the value is in pf. Therefore, we have:

150,000pf = 150nf = .15uf

J is the tolerance: +/- 5% and +/- 10%

250=250 Volts

Thanks Jetadm123. I have ordered caps and tr's from Digikey. I'll let you know how it goes when they arrive.

[PlainBill]

Re: My Viewsonic VX924 monitor died!

Sorry about the missing 'v' PlainBill. I've got a sticking v key on my laptop. I have found something that looks suspicious; the capacitor C24 is not an electrolytic but it looks bulged to me. It has the markings H154JH 250MPP1. Any ideas what this is? If this had blown, would it have caused the shorting of the two tr's? I have not managed to find a circuit diagram for this board, so I'm groping in the dark a bit.

Bingo!!! A bad poly cap will cause the transistors to fail.

If I recall correctly, the Belinea 101910 service manual is available, and is an exact match for this monitor.

PlainBill

[jetadm123]

Re: My Viewsonic VX924 monitor died!

Sorry about the missing 'v' PlainBill. I've got a sticking v key on my laptop. I have found something that looks suspicious; the capacitor C24 is not an electrolytic but it looks bulged to me. It has the markings H154JH 250MPP1. Any ideas what this is? If this had blown, would it have caused the shorting of the two tr's? I have not managed to find a circuit diagram for this board, so I'm groping in the dark a bit.

If it's the orange cap, then it's a poly cap. Replace both as these have been known to fail.


Hopefully, this makes sense. The "154" is capacitor code for:

15 is the cap value followed by the multiplier (in this case 4 zeros) and the value is in pf. Therefore, we have:

150,000pf = 150nf = .15uf

J is the tolerance: +/- 5% and +/- 10%

250=250 Volts

[jfr1326]

Re: My Viewsonic VX924 monitor died!

A denture? No, but it will be an adventure. There are several possible causes for the shorted transistors. Check all points for bad solder joints, resolder the transformers, check all diodes, etc.

I have one of these but all replacement transistors short as soon as power is turned on. The transformer passes a ring test, no diodes are shorted. I haven't been able to identify the cause YET, but it's on my 'to do' list.

PlainBill

Sorry about the missing 'v' PlainBill. I've got a sticking v key on my laptop. I have found something that looks suspicious; the capacitor C24 is not an electrolytic but it looks bulged to me. It has the markings H154JH 250MPP1. Any ideas what this is? If this had blown, would it have caused the shorting of the two tr's? I have not managed to find a circuit diagram for this board, so I'm groping in the dark a bit.

[jfr1326]

Re: My Viewsonic VX924 monitor died!

The transistors marked "DK" are 2SC4672 manufactured by Rohm and are readily available at digikey.com. Also, remember to replace them in pairs.

Thanks a lot Jetadm123. I'll go buy them.

[PlainBill]

Re: My Viewsonic VX924 monitor died!

My vx924 has the normal flashing led symtoms and I've followed this thread with interest until I reached the above. I then found two of the four transistors marked DKQR have shorted causing the smps to keep dropping out. Any ideas what these transistors are and where to get them? Why will this be an adenture?

A denture? No, but it will be an adventure. There are several possible causes for the shorted transistors. Check all points for bad solder joints, resolder the transformers, check all diodes, etc.

I have one of these but all replacement transistors short as soon as power is turned on. The transformer passes a ring test, no diodes are shorted. I haven't been able to identify the cause YET, but it's on my 'to do' list.

PlainBill