Chimei CMV221D black screen ?

[mattclanga]

G,day
I have a chemei CMV221D 22inch LCD monitor When turned on and running works fine. After about 10minutes to half an hour screen turns black but LED stays green. by turning LED (on/off switch) off then on again it resumes running fine for another 10mins then screen turns black again.
It certainly stays on longer than a few seconds. Has anybody expierienced same problem or has a fix
thanks

[PlainBill]

Re: Chimei CMV221D black screen ?

G,day
I have a chemei CMV221D 22inch LCD monitor When turned on and running works fine. After about 10minutes to half an hour screen turns black but LED stays green. by turning LED (on/off switch) off then on again it resumes running fine for another 10mins then screen turns black again.
It certainly stays on longer than a few seconds. Has anybody expierienced same problem or has a fix
thanks

Testing... testing.... testing... Sorry, the crystal ball isn't working today. We'll have to do this the hard way.

The symptoms suggest something is overheating, rather than a 'hard' failure such as a bad CCFL or shorted transformer. Open up the monitor and attach a good picture of the power supply / inverter board. If you see several capacitors that are trying to imitate Mt Vesuvius, plan on replacing caps.

PlainBill

[PCBONEZ]

Re: Chimei CMV221D black screen ?

Common failure mode.
I've done that one more with laptops in which it's usually a bad inverter or tubes.
Desktop screens are a bit different and it could be a PSU issue too.
There are 4-5 folks in here that are experts at desktop LCD screens.
[But that wouldn't be me.]
Post [upload] some pics of the PCB[s] in the thread here and odds are one or two will jump in and start helping you figure it out. [Use the "Go Advanced" button below and you'll see how to upload pics.]
.

[PCBONEZ]

Re: Chimei CMV221D black screen ?

PlainBill <- Yeah! You are saved! He's one of them screen experts.

[mattclanga]

Re: Chimei CMV221D black screen ?

Thanks for the reply's
find attached photo's of board. after reading some posts about changing bulging caps i had a go at changing one that looked a bit dodgy. it was the one next to the fuse. i re-assembled and still the same fault.
If more photos or info required let me know.

This is a bit different to working on 600 ton mining equiptment

[Bobdee]

Re: Chimei CMV221D black screen ?

That looks the same Power suppy/Inverter as this Thread
https://www.badcaps.net/forum/showthread.php?t=8265
Might help with Common faults

[PCBONEZ]

Re: Chimei CMV221D black screen ?

Thanks Bobdee - That does look like the same board.

Often different makes/models use the same PCBs. That's another reason these guys the see lots of screens are so handy. They may never have seen your screen but they might have seen the same board in a different screen.

[PlainBill]

Re: Chimei CMV221D black screen ?

Nice pictures. The question I have is this a failure of the backlights, or a failure of the logic card / panel? I have two tests to suggest.

The first is easy. When the screen goes black try viewing it from an angle while shining a bright light on it. If you can see the desktop (or whatever you were viewing when it went black), it's almost certainly a backlight problem.

The second is a little more demanding. Check the voltage from the small pigtail fuse near the center of the board to the metal fram of the monitor. Does it change when the screen goes black.

PlainBill

[mattclanga]

Re: Chimei CMV221D black screen ?

Thanks for guidance
First test - screen went black 15 minutes after power up shone torch on screen looked from side and nothing
Second test - measured voltage from pigtail fuse circled in red to metal body 19.5 volts when screen went black voltage increased to 21.6 volts.
When screen working buzzing noise coming from part circled in green.

[PlainBill]

Re: Chimei CMV221D black screen ?

Thanks for guidance
First test - screen went black 15 minutes after power up shone torch on screen looked from side and nothing
Second test - measured voltage from pigtail fuse circled in red to metal body 19.5 volts when screen went black voltage increased to 21.6 volts.
When screen working buzzing noise coming from part circled in green.

It might be a bad transformer, or it might be bad glue. The glue around the capacitors has been blamed for problems with inverters. Scrape it all away and see if that fixes it.

If that doesn't do it, I would like top and bottom pictures of the area around the connector that links the power supply / inverter to the logic card.

PlainBill

[mattclanga]

Re: Chimei CMV221D black screen ?

Thanks Plainbill
I removed glue from around caps and the fault is still present. Have attached pics of underside of board. Should i be replaceing all of the caps as a matter of course.

[Agent24]

Re: Chimei CMV221D black screen ?

Did you ever find out what was wrong? I seem to be getting a similar problem myself with a CMV-221D.

[Cpt_AaronB]

Re: Chimei CMV221D black screen ?

I am wondering also. I reformatted my comp and now my second monitor will not work. It started out going black after awhile and now I cannot get it to come on at all. I really do not want to have to go get an new monitor if it is an easy fix.

[Agent24]

Re: Chimei CMV221D black screen ?

I am wondering also. I reformatted my comp and now my second monitor will not work. It started out going black after awhile and now I cannot get it to come on at all. I really do not want to have to go get an new monitor if it is an easy fix.

If you've got a problem with your own monitor, please start a new thread in the monitor section detailing what brand and model your monitor is, what is wrong, what you have tried etc.

Opening it up and uploading photos of the insides would also help.

[cashkennedy]

Re: Chimei CMV221D black screen ?

I picked up one of these CMV221D's cheaply on craigslist with just the buzzing noise, after a few weeks it got to be louder and the backlight started flickering a little / not putting out a consistent brightness, so i figured it was time to operate.

Caps c200 , ce101, ce102, ce103, ce105 all look bulged and are all CapXon. Crackling noise appears to come from around the backlight transformers though as other people have mentioned.

After replacing c200, ce101, ce102, ce103 with Panasonic FM/FC caps the noise is significantly decreased and the backlight no longer flashes or strobes in different intensities. The remaining noise occurs generally only when i turn the screen on / or off or resize the resolution of the screen (probably causes a on / off for the screen as well to adjust) and the noise only lasts less then a second.

Gonna see if i can order a replacement for ce105 (the 2200uf cap) that will fit in the space (panasonic FM caps seem to always be bigger then what they replace ). Hoping that the fact that the noise occurs primarily while switching on / off indicates this is a cap issue, and not a bad transformer.

Will report back if problem gets worse again (my fear), or if it stays the same / goes away compleatly after replacing the 2200uf cap.

[retiredcaps]

Re: Chimei CMV221D black screen ?

Caps c200 , ce101, ce102, ce103, ce105 all look bulged and are all CapXon.

You didn't supply a picture or say how many caps there are in total, but 5 bad Capxon caps is enough to replace them ALL due to guilt by association.

[cashkennedy]

Re: Chimei CMV221D black screen ?

People above have posted pics and list of the caps so I didnt figure it was very important. Plus Im too much in a rush to start soldering to ever take a picture before i start removing the bad caps, and your lucky i got some pics after i was done. Plus my phones camera is bad lol (learned lesson about compressed air and ccd)

There's around 9 electrolytic caps on this board
-1 is the huge ac filter cap that is fine
-2 are from some more reputable brand (i think it might have been nichicon, they are the green ones that are in the lower right of board/ left of picture) one is 1000uf 10v and one is 330uf 25v
-the rest are all CapXon caps that are buldging. (3x 220uf 25v, 2x 1000uf 25v, and 1 x 2200uf 10v)


As you see from the closeup i replaced them all with panasonic caps except the 2200uf one that you can still see is buldging in the pics. You can also see my bad soldering job on the one on the left of board (top of pic) that is slightly unevenly seated on the board

[retiredcaps]

Re: Chimei CMV221D black screen ?

People above have posted pics and list of the caps so I didnt figure it was very important.

Manufacturers change board revisions or even completely with a new design, but keep the same model number.

Plus Im too much in a rush to start soldering to ever take a picture before i start removing the bad caps, and your lucky i got some pics after i was done.

About once every 2 weeks, we have someone who doesn't take a picture or write down a "cap map" and ask what capacitors go into which holes because they forgot or were in a rush.

There's around 9 electrolytic caps on this board
-2 are from some more reputable brand (i think it might have been nichicon, they are the green ones that are in the lower right of board/ left of picture) one is 1000uf 10v and one is 330uf 25v

If the green ones are Samxon GF series, they are a problematic series. So you have more than a 50% failure rate in caps (5/9), this would suggest that the other 4 can't be far behind in failure. In addition, the cost of an extra 4 caps is probably $2.50?

[cashkennedy]

Re: Chimei CMV221D black screen ?

Jeez I feel like im being attacked! I will assume it's out of love though!

I dont know the board revision / Since all the posts on the model matched mine I didnt check revision / board part number.

I did write down a schema of where each cap went and what it's capacitance and voltage were before beggining, and also to aid in ordering parts. Plus while soldering i remove the same types, replace, then go on to the next type.

Next time i take it appart i will look if they are Samxon GF, otherwise im not really a strong proponent of the replace all caps lifestyle, unless the problem persists / or you know the brand is questionable. Which is partially because these repairs are being done for my own items, not for stuff i plan to sell. If i was selling it / with some sort of warranty, I would probably want to do them all.

[Agent24]

Re: Chimei CMV221D black screen ?

The capacitors are so cheap why only replace some? It makes more sense to replace them all at once, and save yourself hassle in the future.

Anyway - what's the model number and revision of your PSU? I have one of these monitors and if it has the same PSU I can try to give you a capacitor list.