Acer AL1916W, can't find the problem

[Phoenix83]

Hi everybody.
Have in my hands monitor AL1916W, but is broken. Both leds (green and amber) lighting at the same time and that's all. I changed the Electrolytic capacitors on the power board. Seems it works, because on the connector to the logic board I measured all the tensions, but slightly different. On the PCB is written +13,8V I measured 14,08 and is written +5V measured 4,97V. I don't know if it can be the problem, don't think so. On the logical board measured 3,29V on both Voltage regulators ABF646 (U6, U7) marked with red circle on the pic. I do not know whether to be both 3.3 V, or one of them is wrong. I have the service manual but for a different model and there is one 3,3V and the other one 1,8V...

Also the inverter transformer is too noisy. I need to build a tester to check it out.

I'm sorry for my english

[selldoor]

Re: Acer AL1916W, can't find the problem

Probably ok but did you check the little white fuse on the main board near the connector to the power board. - Can you post picture of the bottom of the power board.

[selldoor]

Re: Acer AL1916W, can't find the problem

There is another small fuse F200? on the back of the power supply?


And another one maybe F300? one has an S (2amps) on it the other a W (4amps)

[Phoenix83]

Re: Acer AL1916W, can't find the problem

Fuse on the logical board is ok, also fuse 200 on the back of power PCB.
Here's photo of the power PCB back

[selldoor]

Re: Acer AL1916W, can't find the problem

And Another - see late edit


So 3 fuses 0ne green one one with and S and one with a W

[Phoenix83]

Re: Acer AL1916W, can't find the problem

I found them. Are fine.

[selldoor]

Re: Acer AL1916W, can't find the problem

I found them. Are fine.

Drat - I love a blown fuse

Also that green fuse is a new type replacement for a fuse with a W, so someone has changed it?

How about testing the secondary windings on the inverter transformer.
Does the backlight ever flash?
Looks like someone has been soldering there as well?? Cant tell for the glue but the middle connectors dont look great.
Power off - meter on ohms 2000 test S1 to S2 and S3 to S4 as in pic

[Phoenix83]

Re: Acer AL1916W, can't find the problem

I think someone has played with this monitor. Friend gave me it, cuz is broken. I only changed the capacitors. The backlight do nothing. Only thing the monitor do is both leds lighting up.

S1 to S2 = 745 ohm
S3 to S4 = 747 ohm

[Phoenix83]

Re: Acer AL1916W, can't find the problem

Shouldn't there be some capacitor? Like above? See pic.

[selldoor]

Re: Acer AL1916W, can't find the problem

Well the transformer seems good - when there is a lull in suggestions I would remove the glue and old solder and resolder it.
Also now we know it has been "played with" check any of the joints that have been resoldered AND the components in case old faulty ones have been put in or caps replaced the wrong way round. Caps that have been replaced also make a list of board numbers C*** and the uf and v values on them and we will try and check they are in the correct positions. - perhaps a tomorrow job ?

[selldoor]

Re: Acer AL1916W, can't find the problem

Shouldn't there be some capacitor? Like above? See pic.

Doesnt look like there has ever been one there.

I would say test the ccfl bulbs on something but as you have no voltages at all
doesnt seem much point yet.

[Phoenix83]

Re: Acer AL1916W, can't find the problem

Well the transformer seems good - when there is a lull in suggestions I would remove the glue and old solder and resolder it.
Also now we know it has been "played with" check any of the joints that have been resoldered AND the components in case old faulty ones have been put in or caps replaced the wrong way round. Caps that have been replaced also make a list of board numbers C*** and the uf and v values on them and we will try and check they are in the correct positions. - perhaps a tomorrow job ?

I'll leave it for tomorrow. I'm already tired.

Thanks

[Rtech]

Re: Acer AL1916W, can't find the problem

Check the mosfets next to the inverter transformer,,they do fail on a regular basis.

[Phoenix83]

Re: Acer AL1916W, can't find the problem

Hi

Here's the list of changed caps
CE101 - 220uF/35 V
CE102 - 1000uF/16 V
CE103 - 1000uF/35 V
CE104 - 1000uF/35 V
CE105 - 2200uF/16 V
CE107 - 47uF/63 V
CE108 - 22uF/50 V
C204 - 220uF-35 V

Tested the mosfets Q205 and 206, seems been OK.

I tested them as follows (out of circuit):
Multimeter on diode test.
1st connect negative lead to the Mostet's source.
2nd connect positive lead to the gate.
3rd moved the positive lead to the drain. DMM should show a short circuit.
4th with the DMM still connected (-to S, and + to D), connect together Source and gate with some wire. DMM should show a open circuit. Then the mosfet should be good.
I do not know of another method, this one I remember from the school.

[Davi.p]

Re: Acer AL1916W, can't find the problem

R105 smd near output connector must be tested, anyway if is ok your problem seems to be on main/scaler board. I'm not able to find datasheet for ABF646 so you must post all 3 pins voltages.
anyway them has no resistors near so must be fixed output..

[Phoenix83]

Re: Acer AL1916W, can't find the problem

R105 = 0,5 ohm
I'm unable to find it too. But I think is something like LM117MPX-3.3.
Here's voltages on that regulators. (pic)

[Davi.p]

Re: Acer AL1916W, can't find the problem

Regulators are surely good, at this point i don't know which steps you can do, if you have an oscilloscope you can test if the quarz osc. is working, if you don't you can try and replace it, but changing blind-like is not funny, last chance is to search for a replacement main/scaler bd or a replacement RTD2120S that i don't have searched but i guess is a mcu, you need one programmed for this monitor model.

[selldoor]

Re: Acer AL1916W, can't find the problem

Hi

Here's the list of changed caps
CE101 - 220uF/35 V
CE102 - 1000uF/16 V
CE103 - 1000uF/35 V
CE104 - 1000uF/35 V
CE105 - 2200uF/16 V
CE107 - 47uF/63 V
CE108 - 22uF/50 V
C204 - 220uF-35 V

All I can find so far is that they all appear to be in the right way round
and that CE107 is meant to be 47uf - will continue tomorrow.

Looking at the back of the board some of the soldering is really bad - I was going to try and find a picture of someone elses board but have not had time.

Please check carefully and resolder as required the red one doesnt look to have any solder on at all!! That may be right but cant tell what is on the other side?

[Davi.p]

Re: Acer AL1916W, can't find the problem

I don't think that those solder joints are bad, it's only a fact of reflections, after those compo. soldered have no influence in monitor functioning, are for filtering noise that psu produces versus mains (electrical net)...

[Phoenix83]

Re: Acer AL1916W, can't find the problem

The solderings are fine, like Davi.p wrote, is only reflections. I do not have an oscilloscope. I'm biding one USB osc. on Ebay.