Backlight problem on a AL1916W

[IRShifty]

I received this power supply board from a guy who wanted a repair on it. I replaced the two caps you see in the picture. I gave the power supply back to the guy, but he had the whole thing taken all the way apart. After reassembly it doesnt go together just right but it does now it power on just fine. Their is still however a problem with the backlights, they do not power on at all. The image can be faintly seen with external lighting. Now I did some research about a fuse keeping the backlights from powering on.

I don't have a lot of experience in fuses but if the red and green circles are fuses then when i test the green one for ohms it passes and the red one does not.

For the Mosfets, the blue one receives ohms through all 3 pins and the pink one does not.

If any of these things would apply to my current problem please let me know. If you think it is something else then lets hear it.

[PlainBill]

Re: Backlight problem on a AL1916W

I received this power supply board from a guy who wanted a repair on it. I replaced the two caps you see in the picture. I gave the power supply back to the guy, but he had the whole thing taken all the way apart. After reassembly it doesnt go together just right but it does now it power on just fine. Their is still however a problem with the backlights, they do not power on at all. The image can be faintly seen with external lighting. Now I did some research about a fuse keeping the backlights from powering on.

I don't have a lot of experience in fuses but if the red and green circles are fuses then when i test the green one for ohms it passes and the red one does not.

For the Mosfets, the blue one receives ohms through all 3 pins and the pink one does not.

If any of these things would apply to my current problem please let me know. If you think it is something else then lets hear it.

Been there, done that. This thread has all the details.

The two components you circled are resistors. The drill is simple. Replace both mosfets, replace the fuse, replace the caps. The fuse is a smd type on the copper side of the board. IIRC, I used a 4A fast blow. The mosfets are available on eBay.

Question: What caps did you use as replacements?

PlainBill

[IRShifty]

Re: Backlight problem on a AL1916W

Thanks for the fast reply Plainbill

I was reading that thread through before I made this one but did not see much about the backlights. I have had your ebay link to the mosfets open for awhile so I have that. Do you think I need to replace the fuse? or only if it is bad? For the replacement caps I used on hand crappy ones. aka radioshack, but they work for now.

[IRShifty]

Re: Backlight problem on a AL1916W

Also, do you know of anyone that has a tutorial or a guide or anything like that on disassembling/reassembling this monitor? I would prefer if it was back together properly. If not then its okay. all the parts will be inside and working.

Edit: reading through the first thread again i am seeing plenty about the backlight. I guess i was in a hurry before. Now i feel dumb for starting a new thread =X.

[PlainBill]

Re: Backlight problem on a AL1916W

Thanks for the fast reply Plainbill

I was reading that thread through before I made this one but did not see much about the backlights. I have had your ebay link to the mosfets open for awhile so I have that. Do you think I need to replace the fuse? or only if it is bad? For the replacement caps I used on hand crappy ones. aka radioshack, but they work for now.

Excuse me while I embark on a minor rant.

There is a famous proverb "It's a poor workman who blames his tools." Like most proverbs, it is only partially true. The most important asset for any workman is his mind. But even a genius needs some basic tools. Fixing monitors isn't difficult, but you need screwdrivers, a soldering iron and solder, wire cutters, and a clear place to work. You also need a multimeter. A cheap VOM will do, although I prefer a move versatile DMM. OK, rant over.

I don't know if it is necessary to replace the fuse. Is it open? If it is, replace it. If it isn't, don't. Use your VOM or DMM. If you don't have one, buy one.

On an additional note, I recently repaired an identical monitor. The damage consisted of: Two caps with bulging tops, a shorted FET, and a blown fuse. I also replaced the rest of the caps because they are a known bad brand and the additional cost was minimal. After I removed them, I tested them with my ESR meter. The two from the inverter failed, the remainder passed.

My conclusion is this inverter has a poor design that stresses the caps. When the caps fail the FETs take an additional load and one or both will also fail, blowing the fuse. Unless you enjoy replacing failed capacitors, shorted transistors, and open fuses, do NOT use inferior capacitors. If for no other reason, consider your reputation.

PlainBill

[EGuevarae]

Re: Backlight problem on a AL1916W

Excuse me while I embark on a minor rant.

There is a famous proverb "It's a poor workman who blames his tools." Like most proverbs, it is only partially true. The most important asset for any workman is his mind. But even a genius needs some basic tools. Fixing monitors isn't difficult, but you need screwdrivers, a soldering iron and solder, wire cutters, and a clear place to work. You also need a multimeter. A cheap VOM will do, although I prefer a move versatile DMM. OK, rant over.

I don't know if it is necessary to replace the fuse. Is it open? If it is, replace it. If it isn't, don't. Use your VOM or DMM. If you don't have one, buy one.

On an additional note, I recently repaired an identical monitor. The damage consisted of: Two caps with bulging tops, a shorted FET, and a blown fuse. I also replaced the rest of the caps because they are a known bad brand and the additional cost was minimal. After I removed them, I tested them with my ESR meter. The two from the inverter failed, the remainder passed.

My conclusion is this inverter has a poor design that stresses the caps. When the caps fail the FETs take an additional load and one or both will also fail, blowing the fuse. Unless you enjoy replacing failed capacitors, shorted transistors, and open fuses, do NOT use inferior capacitors. If for no other reason, consider your reputation.

PlainBill

I have repaired some units that use that very same PSU/Inverter board (Acer and Westinghouse), and as per PCBONEZ suggestion, I replace the MOSFETs in pairs even if only one failed. As per the fuse, it is/was always blown. And for the caps, you are already there, so change them all just as a precaution, as the cost is minimal and you might avoid reopening the unit again just for another cap (especially when the caps are a known bad brand).

[IRShifty]

Re: Backlight problem on a AL1916W

alright alright, ill stop being lazy and open the wallet to save time =)

[EGuevarae]

Re: Backlight problem on a AL1916W

alright alright, ill stop being lazy and open the wallet to save time =)

[dondrusco]

Re: Backlight problem on a AL1916W

I have repaired some units that use that very same PSU/Inverter board (Acer and Westinghouse), and as per PCBONEZ suggestion, I replace the MOSFETs in pairs even if only one failed. As per the fuse, it is/was always blown. And for the caps, you are already there, so change them all just as a precaution, as the cost is minimal and you might avoid reopening the unit again just for another cap (especially when the caps are a known bad brand).

Hi,

I have the same issue - and step-by-step I found, that:
1, two 220uF/25V caps bulged - exhcanged all
2, fuse Fxx1 blown - I decided to use 3,15A
When fuse was changed - backlight starts 'clicking'

3, one of 40T03GP MOSFET-s dead (shorted)
I decided to exchange both FETs - as you suggest.