Acer AL1917 restarting

[Behemot]

When I first got it, it didn't work at all - blown rectifier and fuse on primary side. After replacing them I just fired it on for a couple seconds, seemed good.

Than I recapped it just for sure (full of Taicon and CapXon), now, when everything is connected, the display powers of for a fraction of seconds, than off and on again over and over. Unpluging CCFL stops this behaviour, I see image using flashlight. Changing all the caps on inverter power supply (various 25V caps, there is up to 24 V on it) back did not help.

This leads me to bad lamp, do you think it's possible? If it was shorted transformer or transistors on inverter side, I think it would not power on at all even without CCFLs connected.

[senndogg]

Re: Acer AL1917 restarting

do you have spare ccfls, just for a try? You know that if the ccfls are aging they drain much power, maybe this puts the system in a restart loop.

[Behemot]

Re: Acer AL1917 restarting

I can open one display I repaired recently. Maybe will take photos than too :-D For a quick try (connecting it from the second display directly into this firsts inverter) that should not be a problem…

[retiredcaps]

Re: Acer AL1917 restarting

Just curious, what voltages do you get across the

1) big filter cap? Is it stable?
2) little startup cap? Is it stable?
3) 5V SB?

when the problem happens?

[Behemot]

Re: Acer AL1917 restarting

Immediatelly as I plug in power cord.

Didn't measure voltage on input cap, but on the outputs everything was smooth (having just the power board alone, data board and CCFL unplugged).

[senndogg]

Re: Acer AL1917 restarting

yes, you can use them from a second monitor.
if you think you will be repairing more and more monitors, you have to collect several ccfls (of different sizes). they will be handy!

[Behemot]

Re: Acer AL1917 restarting

Well U usually resell whole display if electronics is bad, never encountered bad CCFLs so far.

[budm]

Re: Acer AL1917 restarting

"Changing all the caps on inverter power supply (various 25V caps, there is up to 24 V on it)" If it really has 24VDC on them, that is way too high for 19" monitor, typical 19" will use 14~18VDC for running the inverter circuits.
You can also use this for testing inverter circuits.
http://s807.photobucket.com/albums/y...g%20old%20CFL/

[Behemot]

Re: Acer AL1917 restarting

24 V without load, than it drops down to 22 V or so.

It has 5 V, 13,8 V for data/audio board, another separate 16-17 V rail and this 22 V for inverter. Most likely for better efficiency. Delta board.

[budm]

Re: Acer AL1917 restarting

Does your board look like this?
http://lcdalternatives.com/Repair-Ki...-P2060847.aspx
It sure does not sound like what you have, the AL1917.
Can we see the pictures?

[Behemot]

Re: Acer AL1917 restarting

Not even close…gimme some time, I have to finish some reviews and computer builds, than I will return to this again

[ben7]

Re: Acer AL1917 restarting

Check to see if there are any pinched HV wires. Also check for bad solder joints!

[Behemot]

Re: Acer AL1917 restarting

Yeeah I checked for cold joints right away, didn't see anything bad. Seems that Delta made good work in soldering.

[ben7]

Re: Acer AL1917 restarting

Check the MOSFETs that drive the transformers.

Is it happening with only one ccfl? or both?

Try changing the startup capacitor too

[Behemot]

Re: Acer AL1917 restarting

Even though there are two transformers in invertor, there is only one tube. At least I believe so. THe thing is, there are another four tiny transformers with CCFL-like connector, and I don't have any idea where it is attached to…

Didn't check transistors but I think if they were bad (short), it would restart/go to protect mode immediatelly, no? They are before the transformers thus still under voltage from the power supply part.

[ben7]

Re: Acer AL1917 restarting

Even though there are two transformers in invertor, there is only one tube. At least I believe so. THe thing is, there are another four tiny transformers with CCFL-like connector, and I don't have any idea where it is attached to…

Didn't check transistors but I think if they were bad (short), it would restart/go to protect mode immediatelly, no? They are before the transformers thus still under voltage from the power supply part.

One could be open circuit.

There must be more than one ccfl in this thing.

Could be get some pictures?

[budm]

Re: Acer AL1917 restarting

Are you sure this is AL1917? Those 4 tiny transformers are the high voltage balancers for lamps.

[Behemot]

Re: Acer AL1917 restarting

Yep, AL1917 C (line below it says: Version: 1917 Cs). Can they change whole interior with new revision??

[retiredcaps]

Re: Acer AL1917 restarting

Yep, AL1917 C (line below it says: Version: 1917 Cs). Can they change whole interior with new revision??

Yes, that is why we always ask for pictures.

[Behemot]

Re: Acer AL1917 restarting

I told ya I cannot do it right now, wait a while, OK? If it is supposed to be any good, I need room, time and equipment for that. I do not have any right now, there are computer parts everywhere and I need to finish this first.