AL196W Acer Monitor- Slightly Different Issue

[Solder Boy]

Hello all before getting into this I did take a look at the AL196W thread that already exists but I didn't quite see anything that resembles the issue I have with the one I am trying to fix ( Either that or I am blind lol)

Briefly C204 is a new cap, and the cap beside C103 is also a new one.

After I replaced these caps and turned it on, all I got was a very brief flicker and that was it. I have a set of working CCFL's as testers, I plugged them in and they didn't even fire. However the green/orange power light was on.

The main filter cap is missing because I initially thought it was bad, will be replacing it.

I have about 6 or 7 of these monitors to look at.

Tested the main fuse.. seems to be okay.. I'm a bit rusty with this been away due to medical reasons..

Any ideas?

[jetadm123]

Re: AL196W Acer Monitor- Slightly Different Issue

If the main filter cap is missing, you should not operate the power supply, since a large amount of AC ripple is going unfiltered and will damage the other components.

[Solder Boy]

Re: AL196W Acer Monitor- Slightly Different Issue

If the main filter cap is missing, you should not operate the power supply, since a large amount of AC ripple is going unfiltered and will damage the other components.

I know that I haven't operated the PSU without it.. I said I'm going to replace it. It was previously installed and that's how I know what it is or is not doing.

[jetadm123]

Re: AL196W Acer Monitor- Slightly Different Issue

Below the inverter transformer in your first photo are two mosfets, Q205 and Q206. Check them for shorts as they are a known problem on your board.

[Rtech]

Re: AL196W Acer Monitor- Slightly Different Issue

And if my memory serves me correctly there is also an SMD fuse on the bottom that blows when the Mosfet/s fail.

[selldoor]

Re: AL196W Acer Monitor- Slightly Different Issue

And if my memory serves me correctly there is also an SMD fuse on the bottom that blows when the Mosfet/s fail.

There is a fuse its a small black one marked N top left in the bottom board picture. Test - meter on ohms probe each end of fuse - should read same as touching the probes together.

[budm]

Re: AL196W Acer Monitor- Slightly Different Issue

Yes, there are two fuses, as jetadm123 has indicated, those two MOSFET's usually shorted out nad blown the surface mounted fuse and some time also takse out the Gate drive resistors and Diodes with them also.
Also check the secondary of the transformer windings.

[Solder Boy]

Re: AL196W Acer Monitor- Slightly Different Issue

Thanks for the input guys.. greatly appreciated will get back to you with my findings soon!

[selldoor]

Re: AL196W Acer Monitor- Slightly Different Issue

Hmm in that case there are 3 (Three! ) fuses. 1x N and 2 x W

[budm]

Re: AL196W Acer Monitor- Slightly Different Issue

Darn selldoor, your good set of eyes see the third fuse, where?
Never mind, I see it now close to the top left.

[Solder Boy]

Re: AL196W Acer Monitor- Slightly Different Issue

I've had a chance to do some measurements:

The N fuse reads normal
The W fuses all read normal as well.

On the transformer it read open on both measuring points as indicated in the edited photo.

The 2 MOSFETS near the transformer both read that they were shorted ( not sure if I tested them right though)

Last time I tried to get a replacement transformer from Delta, they told me I was out of luck.

[selldoor]

Re: AL196W Acer Monitor- Slightly Different Issue

Can you do a close up pic of the w fuses

Mosfet test from retiredcaps 2 seconds to black guide
https://www.badcaps.net/forum/showthread.php?t=10419- worth reading
start at post 19
Mosfets

If you have a manual range multimeter, set it to 200 ohms (two hundred). This is for 3 pin ICs only. You can test a mosfet (Q, IC designation) "in circuit" by (power off and unplugged)

a) black on pin 1- red on pin 2 - record ohms
b) black on pin 1- red on pin 3 - record ohms
c) black on pin 2- red on pin 3 - record ohms

If any reading is less than 30 ohms you might have shorted mosfet. Remove from circuit and repeat the tests to verify.

Some mosfets are more than 3 pins. To test those, identify the part number and search for its datasheet. Once you find the datasheet, the pins will be designated source (S), gate (G), and drain (D). It will probably be documented as S1, S2, G1, G2, D1, D2.

Simply test

a) black on pin S1- red on pin G1 - record ohms
b) black on pin S1- red on pin D1 - record ohms
c) black on pin G1- red on pin D1 - record ohms

Repeat for the "2" pins. That is S2-G2, S2-D2, G2-D2.

Note: a shorted mosfet would likely cause a very brief flash of the backlight or no backlight.


Transformer - Unusual for BOTH to be open check that your meter was on 2000 ohms
and also that there was no lacquer on the pins like in Budms picture scrape down to bare metal

[Solder Boy]

Re: AL196W Acer Monitor- Slightly Different Issue

Thanks for the additional input selldoor, will do the additional measurements tomorrow.

Regarding the transformers I did peel off the silicone, will use a different meter.. the one I used didn't have a selector switch.

As I said earlier.. little rusty doing this.. hadn't done much service work lately.

[budm]

Re: AL196W Acer Monitor- Slightly Different Issue

If you find out that this monitor has bad the transformer, shorted out MOSFET's, blown fuses, needs a set of caps, and hope that it does not have bad lamp/s. You may want to total up all the parts to see if it is worth to repair it not. But for learning how to troubleshoot the problem, that will be priceless.

[Solder Boy]

Re: AL196W Acer Monitor- Slightly Different Issue

If you have a manual range multimeter, set it to 200 ohms (two hundred). This is for 3 pin ICs only. You can test a mosfet (Q, IC designation) "in circuit" by (power off and unplugged)

a) black on pin 1- red on pin 2 - record ohms Open

(b) black on pin 1- red on pin 3 - record ohms Open
(c) black on pin 2- red on pin 3 - record ohms Resistance varied then read open.. 2nd Mosfet read 176 then instantly read open
If any reading is less than 30 ohms you might have shorted mosfet. Remove from circuit and repeat the tests to verify.



Transformer - Unusual for BOTH to be open check that your meter was on 2000 ohms
and also that there was no lacquer on the pins like in Budms picture scrape down to bare metal

I used my digital MM with a selector switch obtained reading of 751 and 749 OHM respectively

I retested the SMD fuses again this morning.. I did find one of the W fuses that read open.

Tried taking a close up of the W fuse in question turned out blurry. If I can get a clear closeup I will post a pic.

[Solder Boy]

Re: AL196W Acer Monitor- Slightly Different Issue

If you find out that this monitor has bad the transformer, shorted out MOSFET's, blown fuses, needs a set of caps, and hope that it does not have bad lamp/s. You may want to total up all the parts to see if it is worth to repair it not. But for learning how to troubleshoot the problem, that will be priceless.

Well it was a learning experience that is for sure, after thoroughly testing the PS board with the help from this forum.. I think it might be a case of not worth fixing.

I'll certainly be a bit more thorough with my diagnostics in the future before I go ordering caps assuming that alone will solve the problem.

[jetadm123]

Re: AL196W Acer Monitor- Slightly Different Issue

You might be able use parts from this monitor to repair the other monitor you're looking at.

[Rtech]

Re: AL196W Acer Monitor- Slightly Different Issue

The transformer readings look Ok now,and normally replacement of the two mosfets and the fuse, would restore it to life.

[Solder Boy]

Re: AL196W Acer Monitor- Slightly Different Issue

The transformer readings look Ok now,and normally replacement of the two mosfets and the fuse, would restore it to life.

I hear you on the mosfets, those I'm sure I can source out but the little W fuse is another story. I have no idea what value it is or even the foggiest idea where I would get it from.

If anyone has knowledge in that dept please let me know

[selldoor]

Re: AL196W Acer Monitor- Slightly Different Issue

Id keep this one as spares and use the other "w" fuse to replace the one in the screen you seemed to quickly set aside as it had a blown "w" fuse?

Try google smd fuse marking