Dead Acer AL2416W monitor, need help choosing replacement caps

[hackdog]

Last week I got an Acer AL2416W monitor (VGA only model) from a friend, exhibiting the "2 seconds to black" problem (the monitor, that is, not the friend). I've read the service manual and this forum on what others had to say about their model, then opened it up and did some structured testing.

I think only the caps on the inverter board are shot:
- Acer logo shows, then disappears
- Picture is faintly visible with a flashlight. Top tip: shine the flashlight while moving a white window around on the PC attached to it -- it's much easier to detect faint movements that are in perfect sync with your hand, than it is to see a static image.
- If I leave the display powered, but turn off the video signal for a few minutes, then turning it back on, it often works normally for a few seconds, then turns back to black. That tells me that the power supply, the video decoder and the CCFL tubes are all OK. And even the inverter briefly works.
- Measured fuses F1, F2 and F3; all are very low resistance, so good.
- Measured MOSFETs Q3, Q4, Q5, Q6: all terminal combinations are infinite resistance, so good.

So all things considered, I think I just need to replace the 10 caps. None look out of the ordinary, but I don't have an ESR meter yet so I can't measure them. I've looked around on a suitable webshop and found two suitable replacement models among their selection: Rubycon 35ZLH100MEFC6.3X11 and 35ZLJ100M6.3X11. Any reasons favouring one of them? The ZLJ is slightly cheaper but that's not a major concern.

[Pentium4]

Re: Dead Acer AL2416W monitor, need help choosing replacement caps

I like to use UCC KY series and Panasonic FC/FM. Can you post some pictures?

[jetadm123]

Re: Dead Acer AL2416W monitor, need help choosing replacement caps

Either Rubycon ZLH or ZLJ should work fine. Might be a slightly tighter fit, since they're a little larger. Also, check the bottom of the original NKCON 100uf 35v caps. You should them bulged out.

[hackdog]

Re: Dead Acer AL2416W monitor, need help choosing replacement caps

Attached are two pictures from the lower and upper side of the inverter board, viewing the caps from the top side. These were taken last weekend; at the moment I can't access the monitor, but I'll post pictures of the bottom side of the caps tomorrow. I think I might get away with using slightly longer caps, as there's some room left.

[retiredcaps]

Re: Dead Acer AL2416W monitor, need help choosing replacement caps

Before replacing the caps, keep in mind, 2 seconds to black is not limited to one problem area. You could have multiple problems with the monitor.

2 seconds to black can be

a) bad caps
b) bad ccfls
c) bad ccfl wiring (especially the return wiring)
d) bad secondary windings on the inverter transformer

More details starting with post #19 at

https://www.badcaps.net/forum/showthread.php?t=10419

Also, see budm's Inverter tester using old CFL

https://www.badcaps.net/forum/showthread.php?t=19987

I suggest you check 2b, 2c, and 2d.

[retiredcaps]

Re: Dead Acer AL2416W monitor, need help choosing replacement caps

- If I leave the display powered, but turn off the video signal for a few minutes, then turning it back on, it often works normally for a few seconds, then turns back to black. That tells me that the power supply, the video decoder and the CCFL tubes are all OK. And even the inverter briefly works.

If I understood what you wrote above, I disagree with your conclusion that the ccfls are good. They could be good, but you can't rule them out by your described symptoms.

The inverter pwm IC works as an "all or nothing". Either all the ccfls work or none at all. During the initial power up, the pwc IC lights up all the ccfls (typically 2 seconds), but if one is bad, all are shutdown.

[hackdog]

Re: Dead Acer AL2416W monitor, need help choosing replacement caps

@retiredcaps: okay, I see what you mean -- even though all CCFLs light up, one or more could electrically behave quirky, which the inverter driver then detects within a few seconds and then shuts itself down. I'll do more testing this weekend before ordering any replacement parts.

But I'm surprised to hear that a CCFL could appear to shine fine, while upsetting the inverter. What sort of characteristic would it show in this case that triggers the driver shutdown? Something like excessive lamp current or ripple?

[kc8adu]

Re: Dead Acer AL2416W monitor, need help choosing replacement caps

i would start with ALL the caps.
the ones you show on the inverter are prone to going high esr and can cause your symptom.but so can a bad tube,transformer,ect.

[budm]

Re: Dead Acer AL2416W monitor, need help choosing replacement caps

The CCFL will still flash on even if the wire is not making contact but sitting real close to it with the end connection of the lamp, the high voltage will arc over to flash the lamp on but it will not be able to sustain the current flow through the lamp so the inverter circuits will shutdown.
http://s807.photobucket.com/albums/y...klight%20lamp/

I can use the CFL to check and see if the HV is present at the output of the transformer or not but it will not tell you if the transformer is good or not since bad transformer can still put out the voltage but not sustaining voltage.
http://s807.photobucket.com/albums/y...t=DSC01236.jpg

[hackdog]

Re: Dead Acer AL2416W monitor, need help choosing replacement caps

I've removed the inverter board and took some closeups of the bung side. Looks normal, no popped bungs, but as they're prone to failure and relatively easy to replace, I'd like to swap them for good ones anyway.

While looking for replacement parts, I've noticed that RS Components unfortunately doesn't deliver to private customers, at least not in Belgium or the Netherlands; the registration process requires an official company registration number. Perhaps this is useful info to add to the where to buy thread. And Digikey's shipping charges alone greatly exceed the cost of the caps themselves, so that's a bit of a shame. Any other recommended webshops that spring to mind where hobbyists can buy a few parts from?

[mariushm]

Re: Dead Acer AL2416W monitor, need help choosing replacement caps

See Farnell : http://be.farnell.com/

Not many Nichicon in stock, but they do have Panasonic and Rubycon. Though I've heard they have some big shipping fees in some countries.. to my country it's a reasonable 3-4 euros.

This site's store does sell some capacitors, check the site's online store, however being sent from US shipping might still be a bit much.. Contact the owner to see if he can give you a deal.

If you really can't find anything convenient, I might be able to mail you some capacitors from my own stock for the Farnell price + about 2 euro for postage and envelope... But again, only if you can't find something... I'm not doing business here.

PS. There's usually a PAIR of cfl lamps on each side of the monitor, so you might see lights showing up on both ends, but one of the lamps on the sides may not light up or may have a bad contact. It's worth checking out first, I've had a 17" lcd monitor recently in which one of the return wires was unsoldered. The panel lit up and then turned off after a few seconds.

Might be worth measuring the resistances in the coils of all small transformers.. if one's resistance is different than the others, it might be the cause of your problems.

[hackdog]

Re: Dead Acer AL2416W monitor, need help choosing replacement caps

With great pleasure I can now announce that I've successfully fixed my monitor!

I figured I'd replace the suspicious caps first, as they can relatively easily be replaced by known good ones. Electronics shop AITEC (aitec.be) told me that they order regularly through Farnell, and so they could include my preferred caps in their next batch. I went for Rubycon 35ZLJ100M6.3X11.

I replaced the caps one by one, forming the legs of each new cap with needle-nose tweezers into S shapes suitable for soldering on the pads. Cleaned off the flux residue with isopropyl alcohol. After final inspection I put the inverter board back in and wired it up. And sure enough, it worked flawlessly!

I'll keep the bad caps in case I get around to test their ESR. Thanks for all your support, and let's hope that the second life of this monitor will be a long one!

[budm]

Re: Dead Acer AL2416W monitor, need help choosing replacement caps

By the way, I just fixed this inverter board yesterday, I heat up those 100uF 35V caps with hairdryer, then the inverter will come on (I do have 24VDC, but the inverter will not run). I replaced them all with Panasonic FM series. If you look at the caps with scope, you will see lots of high frequency on those caps.