Need some advice on which caps to replace.

[Vinhlol]

Hello everyone,

I stumbled upon this forum after searching for a way to fix my old monitor.
It used to flicker a lot but nowadays it randomly shows a black screen for a few minutes before turning back to normal. (sometimes the green led is blinking)

I'm guessing I need to replace the caps because I disassembled the monitor and found out that all the caps are from Capxon and I found a vid about the same monitor on youtube: http://www.youtube.com/watch?v=fT9H2bn0Lio (the board does not look the same though)

Do I need to replace all the caps including the purple ones? because I can't seem to find any good replacement caps with the same size for those.
And if I have to replace them all, does someone know how to easily remove the white stuff?


Pictures:

Overview: http://i.imgur.com/TcRcRij.jpg

Purple caps: http://imgur.com/GOmup3C

White stuff: http://imgur.com/yLUEgTu


Capxon SZ series
150uf 25v 8x7 340 ripple 0.40 impudence
Replacement:???????????????????

Capxon KF series
470uf 25v 10x16 1200 ripple 0.076 impudence
Replacement: http://nl.rs-online.com/web/p/alumin...itors/7497202/

Capxon KF series
100uf 25v 6.3x11 370 ripple 0.35 impudence
Replacement: http://nl.rs-online.com/web/p/alumin...itors/7497199/

Capxon KM series
470uf - 10v - 8x11.5 - 290 ripple - ??? impudence
Replacement: http://nl.rs-online.com/web/p/alumin...itors/7442000/

Please confirm if the replacement caps I found are good.

Cheers

[mariushm]

Re: Need some advice on which caps to replace.

The white stuff is glue, you can scrape it away.

The Capxon capacitors are bad but they don't look like they're breaking down. Still, I would replace them

Don't worry too much about the size, as long as you can safely put the lid back, you can use taller capacitors. Just make sure the diameter of the new capacitors is not too large, so large that they wouldn't fit in the place you have there. You could even put capacitors on their side on the pcb if they're too tall.

The capacitors you selected are decent but I'd go for panasonic FM or FR just because they have better tolerance to heat. They're much better in specs but they should still work fine.

The transformer on the top left seems like it overheated or heats up more than the other one during use.
This could be a sign of a bad capacitor (the pink one below it) but could also be a sign of dying cfl tubes which pull more current from the transformer.

Double check the area around that hot transformer and if you see something that looks like it may not be soldered properly, it might be worst touching up that spot by adding a bit of solder to make sure it's soldered properly.

ps. You can use capacitors rated for 35v or 50v for those 150uF 25v capacitors. In general, you can choose capacitors rated for higher voltage. I also think it would be safe to use 180uF-220uF capacitors instead of 150uF for those 2 particular capacitors, it shouldn't affect the monitor negatively.
For example this looks ok : http://nl.rs-online.com/web/p/alumin...itors/5261632/

ps2. If you have room on the board, just use 470uF 25v instead of 470uF 10v - get a pack of 5 or 10 470uF 25-35v and you're done. No need to get two different ones unless you really can't fit a 25/35v rated one in that place.
ex :
http://nl.rs-online.com/web/p/alumin...itors/7083721/
http://nl.rs-online.com/web/p/alumin...itors/5261553/
http://nl.rs-online.com/web/p/alumin...itors/7396822/
http://nl.rs-online.com/web/p/alumin...itors/7083945/

[Vinhlol]

Re: Need some advice on which caps to replace.

So I finally managed to replace the caps using my sloppy soldering skills (1st time using a solder) and it seems like my monitor is working again!

(ignore the yellowish tint. it's from f.lux)

Let's just hope it doesn't randomly show a black screen again.

Thanks for the advice Mariushm!

[Vinhlol]

Re: Need some advice on which caps to replace.

Hey guys,

It seems like replacing the capacitors did not fix the problem.

The monitor works but after using it for a while it randomly goes to a black screen with the green power led blinking.
Then after a while the monitor goes back to normal.

Anyone has a clue what the problem could be? Should I just get rid of the monitor?

[momaka]

Re: Need some advice on which caps to replace.

Given the pink hue, either the CCLFs are at the end of their life or the inverter isn't working properly.

[shovenose]

Re: Need some advice on which caps to replace.

Given the pink hue, either the CCLFs are at the end of their life or the inverter isn't working properly.

Um no, read his post.
http://justgetflux.com/

[momaka]

Re: Need some advice on which caps to replace.

Ah okay, I see. I thought that f.lux was typo or something and so I read over it. (And I have a CRT monitor, on which I can turn the brightness down quite a lot for night viewing, so that f.lux stuff is irrelevant for me ).