Help opening Acer AL1916 monitor

[(*steve*)]

I have one of these LCD monitors that turns on OK, then the screen goes dark and the power light flashes on and off.

I'm going to have a bit of a poke around inside, but I can't get the cover off.

Any ideas?

Any ideas about the fault? I'm leaning toward it being a backlight inverter issue.

 

[Mitchekj]

http://www.go-gddq.com/upload/2009_06/09060313346662.pdf

I was going to ask if it was sonic welded together before I found that. Page 26 outlines the procedure. They even include a board layout, and schematics, neat! Why can't more companies provide this stuff?

If I were to guess, it sounds like the monitor is losing/not getting an "ok" signal from the video card, since the power light is flashing.

 

[(*steve*)]

Thanks for pointing me at the manual -- I googled for ages and didn't find that one.

The only problem is that my monitor does not have the 9 screws to release the back. There are no visible screws once the stand has been removed.

I've tried "unsnapping" the back cover by sliding a thin screwdriver in there, but it's really stubborn and I've already made several marks in the plastic.

Incidentally, this is the same monitor that required eprom reprogramming whilst in warranty, and there are no marks whatsoever from that, so there must be some *magic* way to get inside. I'd prefer to find that before I break something opening it with brute force

...15 minutes pass...

Success!

I made a few rounded pieces of thin plastic from a fruit juice container and slipped them into the join. The clips "popped" without any damage to the plastic.

For the first few I had to slip in another shim of plastic to stop them popping back together, but as I moved around the bezel, this was no longer necessary.

 

[(*steve*)]

Edit: The shims were made from PETE plastic (it has a 1 inside the recycle triangle)

Well, I stuffed that up, didn't I.

 

[(*steve*)]

It looks like I have the boxed set of swollen capacitors.

Anyone think these might be a problem?

Almost all of them rated 470uF 25V 105C. All manufactured by "CapXon"

Sorry the photos are a bit rubbish, but you should get the idea.

 

[(*steve*)]

OK, all of those capacitors had a measured ESR of between 5 and 7 ohms, and capacitance of about 1/4 or less than their rated values.

The new capacitors have ESR of 0.08 ohms and the correct capacitance (for 470uF/25V) and ESR of 0.12 ohms (for 470uF/10V).

Unfortunately I couldn't see the other capacitors and from their size, assumed they were 470uF 35V, so I won't be able to replace them until tomorrow when I get some 1000uF 10V low ESR caps.

Normally I would have removed them and verified what they were, but SHMBO hurried me up

I'm actually quite surprised that the replacement caps are almost exactly the same size. When doing this trick on motherboards it has often been the case that the replacements were physically larger.

Oh, the replacements are branded "Suntan", and they don't seem to feature the same way as "CapXon" do in google

 

[Resqueline]

Ah, modern times... How long must we live with this modern "disease"..?
Sometimes it's quite a challenge to find a store that sells caps with better ratings than the originals, and that still fits.
Get physically larger caps if you can. I general the bigger they are the higher their ripple current and lifetime will be. Going up in either capacitance or voltage will do the same trick.

 

[(*steve*)]

I think we must live with this modern disease until price is no longer the driving force in manufacture.

I would hate to think that such faults could occur in medical equipment, but I fear they may not be immune.

Alas in most cases, the components are so close together that replacements which are not the same size cause huge problems. I had a motherboard that ended up with capacitors at odd angles on on their sides to fit the smallest replacements I could find. In high frequency applications (i.e. some of these switchers) the added inductance in the longer capacitor leads can apparently be an issue too

With this power supply, I am extremely limited in the width of the replacements, and somewhat constrained in height (I might be able to get away with an additional 2 or 3 mm).

Having only recently built a decent ESR meter, and also having only recently obtained a decent capacitance meter, I was *extremely* shocked at the results of measuring some of these capacitors. Even the least physically damaged was bad as the one which seemed to have the most minor of domed tops.

It makes me wonder how bad these capacitors get before they show physical signs.

 

[Mitchekj]

Aluminum caps aren't really that bad if you make all efforts to reduce ripple current and keep the temp down. Unfortunately, that means more components, which means more cost, which means it's not going to happen, so we'll keep seeing these things die.

There's just no fixing the whole, "I need a widget. Widget A sells for $20. Widget A' sells for $15. No brainer."

 

[(*steve*)]

Gee I'm glad there's a local supplier open on Sundays

The 1000uF/10V replacement low ESR capacitors are narrower and taller than the originals. I noted before that I had about 3mm to play with... Well these used every mm of that. They are almost touching the top cover of the PSU, but that is lined with plastic, so it's not a huge deal.

The smoke test passed and the monitor starts up properly.

In further tests, it runs without shutting down (previously it would display the startup image then start flashing the green power light)

Looks like it's fixed.

 

[Mitchekj]

Nice. Love it when something comes back to life. That feeling is what has kept me in the electronics field all these years.

So it would seem the controller was shutting down since it detected an out of tolerance supply voltage? Curious if you'd delved any deeper into the root cause.

 

[(*steve*)]

A second monitor also fixed -- same problem, but not quite as bad (the monitor still worked most of the time).

Those with eagle eyes may note the obvious mistake in my first repair job that I fixed after taking the above photo.

However one of the capacitors was not bad, and I was able to confirm ESD and Capacitance close to the values of the replacement.

ESD of the others was in excess of ten times larger and capacitance about one tenth of the rated amount.

 

[(*steve*)]

Curious if you'd delved any deeper into the root cause.

I think the root cause is likely to be ripple current and temperature.

These monitors were a pair that were on 24/7 for the best part of 4 years. They were replaced within months of each other and moved to locations where they were rarely used (on servers and almost always turned off).

The circuit diagram I have suggests that a NCP1203D60R2G is used for the switchmode controller. The actual boards use a 28 pin device with a part number that I couldn't read on the first board and forgot to read on the second.

Whilst the circuit diagram doesn't suggest it uses anything more than the chip's short circuit protection, the newer (I assume) boards I have seem to contain a lot more stuff in SMD on the rear of the board. I would not be surprised if it has overvoltage or other protections built in.

It is interesting that the monitor that had totally failed continued to power up and display the ACER logo before shutting down. It may well be that the signal to shut down comes from the logic board (and I've not looked at that at all).

The very small amount of research I've done indicates that the power supply board *may* be a third party module. Flashing power LEDs seem to be a very common symptom of "dead" LCD monitors, so it may well be that several manufacturers are using similar power supplies and logic.

 

[jerryg50]

I have one of these LCD monitors that turns on OK, then the screen goes dark and the power light flashes on and off.

I'm going to have a bit of a poke around inside, but I can't get the cover off.

Any ideas?

Any ideas about the fault? I'm leaning toward it being a backlight inverter issue.

A common cause in these monitors, there are a number of electrolytic caps in the power supply area that become thermo sensitive over time. When they heat up they go out of spec. Going from memory there are something like 8 to 12 of these caps. If you are experienced at servicing, you can verify them using a heat gun, freeze spray, and testing with an ESR meter. It will involved a few hours of work to service this.

The explanation above does not rule out any other potential faults. I am explaining the most common cause that I have seen. Giving the monitor for out of warranty service would not be feasible when a new one can be bought for very cheap.


Jerry G.

 

[(*steve*)]

It was.

Replacing the swollen and no longer low-esr capacitors in the power supply rectified the problem in 2 similar monitors.

Perhaps you could put your talents to use on more recent posts