Acer AL1913W, bad PSU, bad inverter, or bad CCFL's?

[justanothercanuck]

I got a pair of Acer 1913w's that seem to have gone south. (I got them that way)

Cracked them open and replaced the caps on the inverter board. Was rather surprised to see through-hole caps being used on a surface-mount board, but I digress. (Must buy alcohol to clean flux.)

But apparently that wasn't enough to get them working. I'll turn them on, they'll try to fire up the backlight a couple times, and go black. The backlight seems to stay on for a fraction of a second when it tries to fire up. Then the LED turns red.

I selectively checked all the bulbs and they appear to be firing up okay, so I know they're not dead (but still maybe dying). They don't stay on for very long if I run them all at the same time, but I noticed they run for a couple more seconds if I unplug one of them (doesn't matter which one).

Unfortunately, they both died in the same fashion, so I can't mix and match parts to get one working, and I'd hopefully like to get both going.

But another thing I noticed was that the light on the power brick dims when I try to turn on the monitor... but that could also be a symptom of the inverter/backlight wanting too much power. Sad thing is, the power brick is sealed, and I can't get it open. I can probably buy new ones though. The bricks do seem to output 19v, but I don't have a load I can connect it to to test it for current.

These things aren't like my Dells, you change a few caps on those and you got a new monitor... These things seem like a chore.

Anywho, the service manual is garbage as usual, so I'm not sure which is at fault... so... bad PSU, bad inverter, or bad CCFL's?

Thanks

[Rtech]

Re: Acer AL1913W, bad PSU, bad inverter, or bad CCFL's?

Can we assume that when you apply a signal from the PC,the Power led changes colour when it recognises the computer, and then trys to switch on,fails and THEN the led reverts to the colour it started with when you first applied Power ????
If that is the case, then you need to measure each of the 8 pins on the connector,for DC Volts..and you need to identify the pin that shows approx 3v when it gets a signal from the PC on switch on,but then disappears when the led reverts to normal (ie the Backlight on Signal).From there we can confirm with another test whether the fault is Inverter or the main board.
You also need to check Resistance on each of the secondaries of each inverter transformer and advise,I would do this first.

[justanothercanuck]

Re: Acer AL1913W, bad PSU, bad inverter, or bad CCFL's?

Sorry, I guess I forgot to mention it doesn't matter if I have a computer hooked up to it, it still blips twice and turns the LED red.

Where do I measure the transformers? There's no pads on the bottom and I'm not exactly sure where to measure on the top...

Thanks

[Rtech]

Re: Acer AL1913W, bad PSU, bad inverter, or bad CCFL's?

The thicker wires on the transformers are the primary,and the thinner ones going out to the Lamp connectors are the secondaries.However I cannot see all the connections from the photo, so suggest as follows.....Number ALL pins on one of the transformers,in any order you wish..then measure resistance from 1-2, 1-3,1-4,1-5.1-6 etc,then 2-3,2-4,2-5,2-6,etc,then 3-4,3-5,3-6,etc then 4-5,4-6 etc, until you complete the readings on all pins,then do the same on all the transformers, the same way,in the same sequence,and advise the results.

[retiredcaps]

Re: Acer AL1913W, bad PSU, bad inverter, or bad CCFL's?

It sounds like you have 2 seconds to black.

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