Acer AL1916W

[zwahelian]

Hey all,

I've been lurking around this forum for the last two weeks as I have recently become interested in repairing dead monitors, and after successfully repairing an emachines monitor with bulging caps, my inexperience got the best of me with an Acer AL1916W. I got two from my corporate office, one dead and one working fine. After replacing the smaller caps on the dead monitor's power supply, I still have a dead monitor. The power LED light doesn't light up at all. I swapped PSU's with the good monitor and it works fine, so at least I've narrowed it down to the PSU. The only capacitor I didn't replace was the big 100uF 450v su'scon. When the PSU is plugged in, I get no voltage from the leads of the large cap with my volt meter. Should I replace the large cap or is there something else that would be causing my woes?

Thank you for any help!

[PlainBill]

Re: Acer AL1916W

Hey all,

I've been lurking around this forum for the last two weeks as I have recently become interested in repairing dead monitors, and after successfully repairing an emachines monitor with bulging caps, my inexperience got the best of me with an Acer AL1916W. I got two from my corporate office, one dead and one working fine. After replacing the smaller caps on the dead monitor's power supply, I still have a dead monitor. The power LED light doesn't light up at all. I swapped PSU's with the good monitor and it works fine, so at least I've narrowed it down to the PSU. The only capacitor I didn't replace was the big 100uF 450v su'scon. When the PSU is plugged in, I get no voltage from the leads of the large cap with my volt meter. Should I replace the large cap or is there something else that would be causing my woes?

Thank you for any help!

Did you check the fuse? (half hidden by the green wire in the first picture).

PlainBill

[retiredcaps]

Re: Acer AL1916W

The power LED light doesn't light up at all. I swapped PSU's with the good monitor and it works fine, so at least I've narrowed it down to the PSU. The only capacitor I didn't replace was the big 100uF 450v su'scon. When the PSU is plugged in, I get no voltage from the leads of the large cap with my volt meter.

Members here hate su'scon and you may want to replace this cap. But before you do, try (with power off and unplugged)

1) test fuse to see if it is open
2) test rectifier to see if it shorted (it is the black long rectangular thing and should be marked with a D on the PCB)

[zwahelian]

Re: Acer AL1916W

The fuse is fine, how do I test the rectifier to see if it is shorted?

[retiredcaps]

Re: Acer AL1916W

The fuse is fine, how do I test the rectifier to see if it is shorted?

With power off and unplugged.

1) set your multimeter on ohm
2) number the rectifier pins 1 to 4
3) put black on 1, red on 2 - record ohm
4) put black on 1, red on 3 - record ohm
5) put black on 1, red on 4 - record ohm
6) put black on 2, red on 3 - record ohm
7) put black on 2, red on 4 - record ohm
8) put black on 3, red on 4 - record ohm

You should have 6 ohm readings.

Do same test as above, but with diode setting AND you want to reverse black and red.

You should have 12 diode readings.

[zwahelian]

Re: Acer AL1916W

Please bare with me... I am a total noob when it comes to this stuff. The multimeter I'm using has many different settings, and I found the resistance tone setting which should give me a tone when touching the leads of the 2A/250V fuse, right? I think I was using it incorrectly and misread that the fuse was fine. I get no tone at all when touching the ends of the fuse. Should I go ahead and order a replacement from digikey?

Also, could someone recommend the most appropriate fuse on Digikey's site?

Will part # F3292-ND or F3297-ND do the trick?


Thanks again, gaining the experience is invaluable.

[BullPar]

Re: Acer AL1916W

What kind of meter are you using? Dont use the tone setting that can give you false readings.

[retiredcaps]

Re: Acer AL1916W

What kind of meter are you using? Dont use the tone setting that can give you false readings.

Agreed. I used the continuity setting and got a false reading on a picofuse. It read 18 ohm and that lead me to believe the fuse was good when in fact it was bad. It depends on the multimeter, but some meters will beep if the measurement is under 30 ohms.

A good fuse should read 0.3 ohm.

Post a picture of your multimeter.

Before you order anything, you should check the bridge rectifier. That may be shorted.

[zwahelian]

Re: Acer AL1916W

Here is a picture of my multimeter.

[zwahelian]

Re: Acer AL1916W

Just to clarify, I should check the rectifier with it desoldered from the circuit board?

[retiredcaps]

Re: Acer AL1916W

Just to clarify, I should check the rectifier with it desoldered from the circuit board?

I test the bridge rectifier in circuit.

[alexanna]

Re: Acer AL1916W

Quick question ,Have we ever determined if the fuse is good?
Al.

[zwahelian]

Re: Acer AL1916W

With power off and unplugged.

1) set your multimeter on ohm
2) number the rectifier pins 1 to 4
3) put black on 1, red on 2 - record ohm
4) put black on 1, red on 3 - record ohm
5) put black on 1, red on 4 - record ohm
6) put black on 2, red on 3 - record ohm
7) put black on 2, red on 4 - record ohm
8) put black on 3, red on 4 - record ohm

You should have 6 ohm readings.

Do same test as above, but with diode setting AND you want to reverse black and red.

You should have 12 diode readings.

with the multimeter set to 200k ohm:

black on 1, red on 2 - infinity
black on 1, red on 3 - 1
black on 1, red on 4 - infinity
black on 2, red on 3 - 1
black on 2, red on 4 - 0
black on 3, red on 4 - 1

red on 1, black on 2 - infinity
red on 1, black on 3 - 1
red on 1, black on 4 - infinity
red on 2, black on 3 - 1
red on 2, black on 4 - 0
red on 3, black on 4 - 1

diode test:

black on 1, red on 2 - 1
black on 1, red on 3 - 1
black on 1, red on 4 - 1
black on 2, red on 3 - .512
black on 2, red on 4 - 0
black on 3, red on 4 - 1

red on 1, black on 2 - .477
red on 1, black on 3 - .517
red on 1, black on 4 - .476
red on 2, black on 3 - 1
red on 2, black on 4 - 0
red on 3, black on 4 - .511

please tell me I did this right.

[retiredcaps]

Re: Acer AL1916W

with the multimeter set to 200k ohm:

black on 1, red on 2 - infinity
black on 1, red on 3 - 1
black on 1, red on 4 - infinity
black on 2, red on 3 - 1
black on 2, red on 4 - 0
black on 3, red on 4 - 1

diode test:

black on 1, red on 2 - 1
black on 1, red on 3 - 1
black on 1, red on 4 - 1
black on 2, red on 3 - .512
black on 2, red on 4 - 0
black on 3, red on 4 - 1

red on 1, black on 2 - .477
red on 1, black on 3 - .517
red on 1, black on 4 - .476
red on 2, black on 3 - 1
red on 2, black on 4 - 0
red on 3, black on 4 - .511

please tell me I did this right.

Please retest the ohm test with your multimeter set on 200 setting (the one just left of the continuity rotary setting). 200k ohm is too high. Pin 2 to 4 will be the interesting one to re-measure.

If pin 2 and 4 on the 200ohm test still shows a low reading (like < 2 ohms), you have a probably shorted bridge rectifier. To verify, remove it from the board and retest out of circuit just to be sure. If it is bad, you will need the model number and replace it.

[zwahelian]

Re: Acer AL1916W

with the multimeter set to 200 ohm:

black on 1, red on 2 - 1
black on 1, red on 3 - 1
black on 1, red on 4 - 1
black on 2, red on 3 - 1
black on 2, red on 4 - .4
black on 3, red on 4 - 1

red on 1, black on 2 - 1
red on 1, black on 3 - 1
red on 1, black on 4 - 1
red on 2, black on 3 - 1
red on 2, black on 4 - .4
red on 3, black on 4 - 1

I will remove the rectifier tonight and retest.

Thanks

[retiredcaps]

Re: Acer AL1916W

with the multimeter set to 200 ohm:

black on 2, red on 4 - .4
red on 2, black on 4 - .4

I will remove the rectifier tonight and retest.

Thanks

Just a FYI, for resistance test, you don't need to reverse the probes.

Diodes are supposed to allow current to flow only in one direction so that is why you need to test the in both directions. One side should read 0.5 to 0.7 and the other reading should be 0L.

This definitely sounds like a shorted bridge rectifier.

[mscott03]

Re: Acer AL1916W

Hey guys- I've been searching for this info all day and glad I found this place! I started to test my rectifier and noticed my numbers were all over the place.

Does anyone have the specific range that all the contacts need to have between the others?

[retiredcaps]

Re: Acer AL1916W

I started to test my rectifier and noticed my numbers were all over the place.

Does anyone have the specific range that all the contacts need to have between the others?

If it reads less than 100 ohm, I would suspect a shorted bridge rectifier. To be sure, you need to remove it and test it out of circuit.

If it is above 100 ohms, the bridge rectifier is probably good.

[mscott03]

Re: Acer AL1916W

OK, I will work on that tonight. Any suggestion on which one / where to order a new rectifier from?

[retiredcaps]

Re: Acer AL1916W

Any suggestion on which one / where to order a new rectifier from?

If you are the USA, try digikey.com. What makes you think that the bridge rectifier is bad in the first place?