Chimei CMV 946A caps

[NobbyJones]

Re: Chimei CMV 946A caps

Yes have found some more pictures of the board now and you are right, there are 2 small caps in the centre. Im fairly new to this and at the risk of sounding useless... are these other caps of a different type as they arent the same as the 6 i have replaced (red-ish coloured) or are they just a different brand?

Unfortunately I am unable to take any better pictures at the moment as my camera has been taken on holiday 8-)

Thanks.

[alexanna]

Re: Chimei CMV 946A caps

The 2 smaller capacitors should be of the low ESR type FM- FC- FR would work well.
Out of the larger capacitors which one did you not replace?

[NobbyJones]

Re: Chimei CMV 946A caps

Next to the 6 I have replaced there is a horizontally mounted cap (see pic in first post), there is also a very large cap near to the mains socket. I havnt touched either of these.

[alexanna]

Re: Chimei CMV 946A caps

So all of the larger capacitors with the exception of the large 450V have been replaced?
Here is how I think I would proceed with you monitor.
Do not disassemble the LCD panel.
Do you have another panel or any spare CCFLs?
I think you may have a problem with CCFLs wiring,
Could you try substituting known good CCFL/s one at a time and see if you can eliminate the flickering/turning off?

EDIT is this the 005 board?

[alexanna]

Re: Chimei CMV 946A caps

One more question if your board is the DAC-19m005.
Is fuse that was marked with a 'w' in thr inverter area still a 4A fast blow fuse?

[PlainBill]

Re: Chimei CMV 946A caps

Next to the 6 I have replaced there is a horizontally mounted cap (see pic in first post), there is also a very large cap near to the mains socket. I havnt touched either of these.

If that horizontally mounted cap is rated at 25 - 35 volts it is very likely part of the inverter supply, and may be the cause of your problem.

The large one near the mains supply rarely fails.

The two small ones near the SMPS transformer cause a variety of problems if they fail. I usually replace them when I replace the rest; they are inexpensive.

PlainBill

[alexanna]

Re: Chimei CMV 946A caps

I misunderstood about what caps were replaced, Yes The horizontally mounted cap is part of the inverter supply,Its most likley a 25v 220uf cap

[NobbyJones]

Re: Chimei CMV 946A caps

Right ive attempted a picture of the board using my phone...

The caps circled in red are the ones I have replaced.

The green, Yellow and Purple ones I have not touched, green is 47uF 50v, cant see what the other two are without getting them out.

When I said the flickering fades out, I meant it gradually gets better over the space of about 15 seconds then stops and is fine, i.e. no flickering - the screen does not go black and none of the backlights go out completely. Sorry if i didnt make that very clear before :P

[NobbyJones]

Re: Chimei CMV 946A caps

Managed to bend the purple cap up enough to read... its a 470uF 25v

[ipman]

Re: Chimei CMV 946A caps

That one can be filtering the rail to the inverter. It can be problematic also.
What brand/series?

[NobbyJones]

Re: Chimei CMV 946A caps

CapXon, so yea I think i'll replace the other 3 that i havnt already

[alexanna]

Re: Chimei CMV 946A caps

Managed to bend the purple cap up enough to read... its a 470uF 25v

I have had been really lucky to work on quite a few of monitors with this power supply, I cannot remember ever seeing a 25V 470UF capacitor in the position of your purple circled capacitor, They have all been 25V 220UF.
However that doesn't mean that in on one of the revisions of the power supply the manufacture decided to change it.
One other thing i have noticed is that when a capacitor is on it's side there always has been an outline on the circuit board to indicate the capacitor is laying flat on the board
The purple circled capacitor also looks different than I usually see, was there any indication that it had already been replaced?

[NobbyJones]

Re: Chimei CMV 946A caps

Right, I've replaced the 3 remaining caps like for like and the flickering is there there.

You say you havnt seen a 470uF cap on this board before? Would it be worthwhile trying a 220uF? There was no evidence that it had been replaced no.

[alexanna]

Re: Chimei CMV 946A caps

Right, I've replaced the 3 remaining caps like for like and the flickering is there there.

You say you havnt seen a 470uF cap on this board before? Would it be worthwhile trying a 220uF? There was no evidence that it had been replaced no.

Have you owned this monitor long enough where the symptom occured when you were using it,or did you inherit it?


If all of the capacitors 12.5mm and lower have been replaced with a good quality ESR type hold off with changing anything yet.
Even though you are not having a 2 second to black problem,I think it would be a good idea to rule out a CCFL problem.Do not dissemble your panel.
Do you have another panel or some spare CCFLs of similar size?

[jetadm123]

Re: Chimei CMV 946A caps

Right, I've replaced the 3 remaining caps like for like and the flickering is there there.

You say you havnt seen a 470uF cap on this board before? Would it be worthwhile trying a 220uF? There was no evidence that it had been replaced no.

There were several revisions of this board and if you had to remove the white adhesive to remove the original cap, then it's probably safe to assume the original cap was 470uf.

What brand/series of replacement caps are you using?

Also, there seems to be a burn mark slightly below right of that 470uf cap.

[NobbyJones]

Re: Chimei CMV 946A caps

No I inherited it a few days ago

All of the caps have now been replaced (appart from the 450v) with Panasonic FC or FR.

Ive tried disconnecting all the CCFL's one at a time on the offchance that one of them was bad, still flickering. I have tried with a CCFL out of another panel and it seems ok but hard to tell whether its flickering or not realy.

I have found a repair kit for these boards on ebay and they include all the caps, 2 inverter mosfets and a replacement fuse. Its obviously not the fuse else it wouldnt work at all? So could the inverter mosfets be causing the problem?

[alexanna]

Re: Chimei CMV 946A caps

So when you leave 3 CCFLs hooked up from the problem monitor and you hook up 1 spare CCFL,Have you looked on the screen of the problem monitor or just the spair CCFL?

[NobbyJones]

Re: Chimei CMV 946A caps

Both, I couldnt say for sure if the external/spare ccfl flickers or not.

[alexanna]

Re: Chimei CMV 946A caps

If you haven done so already try the spare CCFL in the other connectors,see if you notice flickering on the image on the screen

[NobbyJones]

Re: Chimei CMV 946A caps

Already tried that and no change.

Oh well I think ill just accept the fact that it flickers for the first 20 seconds, its not a major problem!

Thanks for all your help guys its much appriciated.