Viewsonic VX2235WM - blank screen on/off

[jetadm123]

Re: Viewsonic VX2235WM - blank screen on/off

One thing to note that even if the capacitance values measure within 20%, the ESR value is more important. Therefore, if the cap value measures okay, but the impedance (ESR) value is too high, it can cause the cap not to perform correctly causing the problems you see. You need an ESR meter to measure the ESR value for each cap.

[Mrx3750]

Re: Viewsonic VX2235WM - blank screen on/off

Yeah, I know. I wish I had an ESR meter, but I don't, and last I checked, they cost way more then I can afford. Well, looking on Ebay now, I see there are some cheapish ones. If I get $60 to blow I'll see what I can do about it.

In the meantime all I have to go by is capacitance and looking for bulging tops. The filter cap may not have been the problem, but it was bulging slightly, and I'm sure enough it was or would become a problem soon.

[budm]

Re: Viewsonic VX2235WM - blank screen on/off

Since the Blue LED is still on, it can be that the Inverter on signal from the main board had dropped out or the inverter circuits had shutdown, or the B+ for the inverter section dropped out. You will need to monitor those signals first to find out what is not present when the backlights go out.

[Mrx3750]

Re: Viewsonic VX2235WM - blank screen on/off

What would cause either of those two symptoms?

[budm]

Re: Viewsonic VX2235WM - blank screen on/off

Failed components, unstable power supply voltage, etc. Cannot tell until you can narrow down what section is bad first. Slightly bulging is not good at all, it means it is failing already. I would replace the set of caps since some already went bad, unstable voltages can cause lots of inconsistent operation.

[Mrx3750]

Re: Viewsonic VX2235WM - blank screen on/off

All right. Where would I test for these voltages? Should I nab pics of the power supply for you, or can you point out the areas I need to check?

[budm]

Re: Viewsonic VX2235WM - blank screen on/off

So right now you do not have any more slightly bulging top caps on the board, right? If you do, then replace them first.
I will need the good clear pictures of the power supply/inverter board, top and bottom sides.

[Mrx3750]

Re: Viewsonic VX2235WM - blank screen on/off

Okay. Tomorrow I'll take out the power supply and grab pics.

No, there are no more bulging caps, and I've pulled out half the caps and tested them, best I could. Replaced a few already even though the ones I pulled out tested fine.

[Mrx3750]

Re: Viewsonic VX2235WM - blank screen on/off

Attached is a shot of the power supply hooked up, and a picture of the underside of the power supply.

Most of the capacitors have been tested using my capacitance meter, and a few were replaced just because I had known good replacements on hand, and wanted to rule them out as a problem. It's gonna be a bit tricky, but where should I connect the multimeter leads, and what voltages should I look for?

[budm]

Re: Viewsonic VX2235WM - blank screen on/off

OK, on the multi-pin connector, the pins are labeled, on my pictures I did not take good pictures that show all the label of the pins. Can you write down what they are?
Here are some of my pictures:
http://s807.photobucket.com/user/bud...tml?sort=3&o=6

[Rtech]

Re: Viewsonic VX2235WM - blank screen on/off

If the Led is still Blue then the monitor can see the input PC signal.So you need to check that the Backlight on Signal is sent from the logic Board to the Psu/inverter.This will be in the region of 3-4 volts DC, and if you have that then it looks like '2 secs to Black' symptoms and follows the sticky.Not all Monitors show a dark image when the Backlights fail so you cannot assume that they are OK.

[Mrx3750]

Re: Viewsonic VX2235WM - blank screen on/off

OK, on the multi-pin connector, the pins are labeled, on my pictures I did not take good pictures that show all the label of the pins. Can you write down what they are?
Here are some of my pictures:
http://s807.photobucket.com/user/bud...tml?sort=3&o=6

Starting from the row of pins closest to the 1000uf 25v capacitor:

EUA
GND
DET
+5V
V_adj
SHUT (I think, it's hard to read.)
ACR+
AOL+

[budm]

Re: Viewsonic VX2235WM - blank screen on/off

Hmm, what is the full model number of this monitor? It should have -1, 2, ect. after the WM. there are at least 9 versions of this VX2235WM.

[Mrx3750]

Re: Viewsonic VX2235WM - blank screen on/off

Nope, no number after the WM. See for yourself.

[budm]

Re: Viewsonic VX2235WM - blank screen on/off

OK, pin 15 on the main board is the INverter on/off pin, it should change state when the monitor is on and when it is off, black probe on the chassis, red probe on pin 15.
I believe this should match your main board.

[Mrx3750]

Re: Viewsonic VX2235WM - blank screen on/off

Ah. Embarrassingly, I'm not that good with schematics. Could you point out pin 15, say in the picture I took?

[budm]

Re: Viewsonic VX2235WM - blank screen on/off

See picture of PIN 15 on the POWER SUPPLY BOARD.

[Mrx3750]

Re: Viewsonic VX2235WM - blank screen on/off

The plot thickens.

I rigged up a jumper wire to pin 15 on the power supply so I could connect my multimeter, and plugged it in. The connector is slightly off kilter now but all pins still make contact. I read 3.01 volts from pin 15 when the display is lit.

Now here's where it gets interesting. I held the monitor on its side for 10 minutes waiting for it to fail and it didn't. Finally my arm got tired and I shut it down.

I'm gonna check the solder joints for the pins on the power supply and logic board.

[budm]

Re: Viewsonic VX2235WM - blank screen on/off

I looked more at the pin out, not sure if it is using pin to pin between main board and the power supply board or not, if it is not pin 15 on the main board may be connected to pin 16 on the power supply board, not 15 to 15, you can get to pin 16 on the top side of the board and check the voltage on that pin also.
Re-flow the solder on those pins is a good idea.

[Mrx3750]

Re: Viewsonic VX2235WM - blank screen on/off

Just got done resoldering every pin on both boards, plugged in the monitor for a quick test and it came up fine. The connection for pin 15 on the logic board looked a little iffy. I'm gonna try running the monitor and see if it fails again. If it does, I'll look at pin 16. If it runs for an hour with no problem, then I might have fixed it.

Edit: Ahhhh nope! Just went out again!