Viewsonic VX2235WM-3 (M220EW01 V0 Panel)

[k3wf3w]

Hey guys, same problem as here

Monitor turns on, but white screen.

F1 is blown, replaced it, and it immediately blew again.

Have done some testing, not really too sure what I am looking for. From what I gather from reading other posts about this problem is there is most likely a short.

So I tested the surrounding caps and the one diode, I made notes on the picture itself, I tested the caps on both the ohm setting and the diode setting (don't know if that helps diagnose the problem or not).

Thanks in advance for any help.

[jetadm123]

Re: Viewsonic VX2235WM-3 (M220EW01 V0 Panel)

The fuse blowing is most likely due to a short. Looking at your readings, you measuring 1.2 ohms across a a few of the caps. That would indicate a potential short. However, other components in the circuit could affect the readings. All those caps on the right side of your photo showing 1.2 ohms appear to be connected in parallel. The sure fire method of checking the caps would be to unsolder/remove them one at a time and recheck their resistance reading to see if they still read 1.2 ohm. Also check C89. That's four caps total you need to recheck.

[Duncanbest]

Re: Viewsonic VX2235WM-3 (M220EW01 V0 Panel)

If you have a power supply with current limited function.

Like this

http://www.elexp.com/tst_3003.htm

Set current 0.1A & voltage 5V , connect to F1 for a while ,the NG part will perform like hot device with finger touch (or using temperature sensor ).

[k3wf3w]

Re: Viewsonic VX2235WM-3 (M220EW01 V0 Panel)

If you have a power supply with current limited function.

Like this

http://www.elexp.com/tst_3003.htm

Set current 0.1A & voltage 5V , connect to F1 for a while ,the NG part will perform like hot device with finger touch (or using temperature sensor ).

Hey, now that is a good idea. But I don't have such a power supply. How important is the Amperage? I have lots of computer power supplies that would provide 5V...

[k3wf3w]

Re: Viewsonic VX2235WM-3 (M220EW01 V0 Panel)

The fuse blowing is most likely due to a short. Looking at your readings, you measuring 1.2 ohms across a a few of the caps. That would indicate a potential short. However, other components in the circuit could affect the readings. All those caps on the right side of your photo showing 1.2 ohms appear to be connected in parallel. The sure fire method of checking the caps would be to unsolder/remove them one at a time and recheck their resistance reading to see if they still read 1.2 ohm. Also check C89. That's four caps total you need to recheck.

ok, took off C89 and it is infinite resistance...
also with it removed the other 3 capacitors mentioned all read 0.9 ohms.
Should I continue removing and testing the other 3?

Thanks for your help.

[k3wf3w]

Re: Viewsonic VX2235WM-3 (M220EW01 V0 Panel)

ok, took off C89 and it is infinite resistance...
also with it removed the other 3 capacitors mentioned all read 0.9 ohms.
Should I continue removing and testing the other 3?

Thanks for your help.

Ok, got bored, so I removed the other 3 caps that were in parallel and guess what, one of them read 0.9 ohms, and the other 2 were infinite. So do you think that was maybe the short?

[Duncanbest]

Re: Viewsonic VX2235WM-3 (M220EW01 V0 Panel)

Too much current -->maybe destroy other part,like burning print circuit copper or something.

[jetadm123]

Re: Viewsonic VX2235WM-3 (M220EW01 V0 Panel)

Not sure what "other 3" you're talking about. Those caps reading .9 ohm appear to be shorted and should be replaced. I would leave them off the board and check all the other caps (there are quite a few of them) on the board for shorts. Make sure you record the location of any other caps that you remove for additional checking.

[k3wf3w]

Re: Viewsonic VX2235WM-3 (M220EW01 V0 Panel)

Oh, the other 2 caps were fine, not other 3. So one of the 3 in parallel were shorted.
I Checked all the other caps in the vicinity and they all read infinite. I also checked all the other caps on the entire board and there were 3 of the larger ones on the far left hand side of the board (not pictured) that read like they might be shorted, but when I removed them from the board and tested them they were fine. There was also another larger one on the far right hand of the board (also not pictured) that read like it might be shorted but that one was fine as well after desoldering and testing it.

So how do I figure out what to replace the bad cap with? Is it by size and color? or do we need a schematic?

[k3wf3w]

Re: Viewsonic VX2235WM-3 (M220EW01 V0 Panel)

Too much current -->maybe destroy other part,like burning print circuit copper or something.

That makes sense, I might get a power supply like you mentioned to make future troubleshooting easier.

Thanks for your help.

[jetadm123]

Re: Viewsonic VX2235WM-3 (M220EW01 V0 Panel)

There are three ways to determine the value, by schematic, scientific method and Wild Ass Guess (WAG) method:

1) schematics are hard to come by for these panels, but you can still try looking for one. You can try looking up the spec sheet for the multi-legged, U4?, chip on the far right of your photo. The manufacturer may have have an applications schematic that might give some insight into the cap values.

2) scientific method: since the caps were in parallel, they're probably all the same value. If you have a capacitance measurement capability on your meter, then all you would need to do is measure the value of a good cap.

3) WAG method: another member has suggested using a cap that's the same physical size as the shorted one.

[k3wf3w]

Re: Viewsonic VX2235WM-3 (M220EW01 V0 Panel)

There are three ways to determine the value, by schematic, scientific method and Wild Ass Guess (WAG) method:

1) schematics are hard to come by for these panels, but you can still try looking for one.

2) scientific method: since the caps were in parallel, they're probably all the same value. If you have a capacitance measurement capability on your meter, then all you would need to do is measure the value of a good cap.

3) WAG method: another member has suggested using a cap that's the same physical size as the shorted one.

hrm, no capacitance capability, there was mention of a schematic on the other thread... I will see if I can find one. Otherwise, WAG will be my only choice. Would it be alright to put in a capacitor that is one size larger (assuming it will fit)? or should I just make sure it is the same size?

Thanks so much for your time. I think I can figure the rest out from here.

[jetadm123]

Re: Viewsonic VX2235WM-3 (M220EW01 V0 Panel)

I think I mentioned U4 in my previous post. You can try looking up the spec shet for U4 in the hope that it contains an applications schematic that might give you a clue regarding cap value.

As for using a physically larger cap, it will probably be the wrong value, but please let us know your progress/results. Good Luck!

[budm]

Re: Viewsonic VX2235WM-3 (M220EW01 V0 Panel)

If they are in parallel with other 3 caps, they will more likely to be the same value, they have to use a bunch of them due to space limitation. You just have to measure one good cap, more likely to be MLCC around 10uf 16~25V rating, becareful when install these MLCC, they are easily cracked and easily damaged.

[Duncanbest]

Re: Viewsonic VX2235WM-3 (M220EW01 V0 Panel)

U4

https://www.google.com/search?client...hannel=suggest

boost function -->from 5V to ?? V (you can measure by meter)
then choose the 0805 MLCC voltage rating

[momaka]

Re: Viewsonic VX2235WM-3 (M220EW01 V0 Panel)

3) WAG method: another member has suggested using a cap that's the same physical size as the shorted one.

Now, I wonder who that is

Yes, I've been using the WAG method for a while now, with high success rate. Had 2 monitors that had this problem about 2 years ago. Both are still working fine after I fixed them. Chances are, your monitor will work even with that shorted cap removed and nothing in its place. However, it's better to add a cap in there anyways. I see another free spot (labeled C27). You can install even an additional cap in there.

At least in my observation, those t-con inverter circuits aren't really all that picky about the caps. As long as nothing is shorted, they will work fine.

If none of the other caps are shorted, just change that shorted cap, put a new fuse, and all should be fine.

[k3wf3w]

Re: Viewsonic VX2235WM-3 (M220EW01 V0 Panel)

Wow, thanks for all the help everyone. I will see what I can figure out. I have a new fuse in and have soldered back in all the caps that were good. I like the idea of putting in an additional cap at C27. It looks like C27 is in parallel with C24, and both C27 and C24 are in series with C23,25,26.

I will keep you all posted.

[k3wf3w]

Re: Viewsonic VX2235WM-3 (M220EW01 V0 Panel)

Here is U4 for those that were interested...

[k3wf3w]

Re: Viewsonic VX2235WM-3 (M220EW01 V0 Panel)

Bad picture, but you get the idea...

So I used caps off a broken motherboard, and I put an extra cap in C27, just because.

Thanks again everyone for all your help. It seems like this is quite a common problem with this particular panel, so I hope this helps others.

[momaka]

Re: Viewsonic VX2235WM-3 (M220EW01 V0 Panel)

I like the idea of putting in an additional cap at C27. It looks like C27 is in parallel with C24, and both C27 and C24 are in series with C23,25,26.

Actually all are in parallel.
But who cares about the details at this point - the monitor is working . Congrats!