Dell E196FPf

[smason]

Hi all, this will be my first attempt at repairing an LCD monitor.
I haven't done much repair work in a long time, so I'm dusting off my gear and hoping for the best.
Equipment available:
My old trusty Fluke 77 DMM, Capacitor Wizard ESR meter, Hitachi scope, and a Blue ring tester is on it's way soon.

Monitor is a Dell E196FPf no backlight. Image is visible on the monitor with a flashlight so I suspect just the inverter, or maybe a bad lamp, though none of the 4 come on at all, even at power up.

2 caps in the inverter section are bulged and have relatively high ESR (2 ohms) other than that no obvious visible signs. Solder joints on the transformers look ok, I'll re-do them though.
I don't see anything that looks like a fuse so far. While I wait for caps, I'll look up some part numbers and test some of the transistors if I can.
Photos are full board, and closeups of the inverter section.
Has anyone worked on this model before?

[PlainBill]

Originally Posted by smason

Hi all, this will be my first attempt at repairing an LCD monitor.
I haven't done much repair work in a long time, so I'm dusting off my gear and hoping for the best.
Equipment available:
My old trusty Fluke 77 DMM, Capacitor Wizard ESR meter, Hitachi scope, and a Blue ring tester is on it's way soon.

Monitor is a Dell E196FPf no backlight. Image is visible on the monitor with a flashlight so I suspect just the inverter, or maybe a bad lamp, though none of the 4 come on at all, even at power up.

2 caps in the inverter section are bulged and have relatively high ESR (2 ohms) other than that no obvious visible signs. Solder joints on the transformers look ok, I'll re-do them though.
I don't see anything that looks like a fuse so far. While I wait for caps, I'll look up some part numbers and test some of the transistors if I can.
Photos are full board, and closeups of the inverter section.
Has anyone worked on this model before?

I believe someone has posted pictures of this (or a similar) combination power supply / inverter / logic board. Or at least something similar to it. A couple of points to check:

U1 in the inverter section - I believe that is the inverter controller. Look for the datasheet.

There should be two signal traces from the logic board portion over to the inverter portion.

Larger pictures of both front and back of the circuit board would help.

PlainBill

[smason]

Originally Posted by PlainBill

Larger pictures of both front and back of the circuit board would help.

PlainBill

Thanks for the reply. I'll try to post bigger photos tomorrow.
I was tempted to get some caps locally (not likely to find good ones here) but sat down and had a beer and the feeling passed

In the mean time my trusty Fluke 77 has flaked out on me, so fixing that while waiting for caps. It doesn't look good, corrosive liquid damage (have no idea what, may have come from a cat...) between the board and the display elastomer. Ugh...

[PlainBill]

Originally Posted by smason

Thanks for the reply. I'll try to post bigger photos tomorrow.
I was tempted to get some caps locally (not likely to find good ones here) but sat down and had a beer and the feeling passed

In the mean time my trusty Fluke 77 has flaked out on me, so fixing that while waiting for caps. It doesn't look good, corrosive liquid damage (have no idea what, may have come from a cat...) between the board and the display elastomer. Ugh...

I had a similar problem with a cat and some electronics. I sat the cat down and explained about stringing tennis rackets.

It didn't help. Cats DO NOT take suggestions.

PlainBill

[smason]

LOL I had the same conversation about tennis rackets.
He muttered something about nylon, and how for a techie, I'm "surprisingly not up to speed on modern polymers", then walked away....

[smason]

Well I'm happy to report that my Fluke 77 survived minor surgery (cleaned the pcb, scraped off the residue from the stuck on elastomer, then tinned the pads as the copper was in bad shape) cleaned the elastomer with isopropyl and a pec pad. re-assembled and to my surprise it works beautifully!
I was so optimistic, I had bids on 2 77s on Ebay

Also the caps for the Dell monitor came in yesterday, and I replaced the 2 bad ones with Panny FMs. Checked the FETs and measured the transformers, all seemed fine.

Just for grins I decided to try it, though I suspected there was more to do, and whaddaya ya know? It works!
I'll leave it on test for a while, then give it back to the owner and tell him he owes me $0.66 for parts.

[PlainBill]

Originally Posted by smason

Well I'm happy to report that my Fluke 77 survived minor surgery (cleaned the pcb, scraped off the residue from the stuck on elastomer, then tinned the pads as the copper was in bad shape) cleaned the elastomer with isopropyl and a pec pad. re-assembled and to my surprise it works beautifully!
I was so optimistic, I had bids on 2 77s on Ebay

Also the caps for the Dell monitor came in yesterday, and I replaced the 2 bad ones with Panny FMs. Checked the FETs and measured the transformers, all seemed fine.

Just for grins I decided to try it, though I suspected there was more to do, and whaddaya ya know? It works!
I'll leave it on test for a while, then give it back to the owner and tell him he owes me $0.66 for parts.

You undervalue yourself. I always mark up parts 20% for my warranty and 10000% for knowing which parts to replace.

PlainBill

[smason]

Originally Posted by PlainBill

You undervalue yourself. I always mark up parts 20% for my warranty and 10000% for knowing which parts to replace.

PlainBill

Yeah, I agree, but this "customer" is a co-worker who gave me a $50.00 gift certificate to my fave restaurant for doing a minor tune-up on his computer last month (which I did on company time ) and another $50.00 last year for a virus removal job, so I don't think he owes me on this one.

Besides this was a learning experience for me, and my first real repair in quite a while.

[garbermf]

Did you replace the parts that are rectangular and about 1"x 3/4"labeled SPW-504 amd TDK0545X. Also where did you order them online.

[Bobdee]

Originally Posted by garbermf

Did you replace the parts that are rectangular and about 1"x 3/4"labeled SPW-504 amd TDK0545X. Also where did you order them online.

The parts you mention are Inverter Transformers
It may help contacting
http://www.lcdrepair.us/
By email I think they may help

[smason]

Originally Posted by garbermf

Did you replace the parts that are rectangular and about 1"x 3/4"labeled SPW-504 amd TDK0545X. Also where did you order them online.

I only replaced the 2 caps, the ones between the transformers. They were slightly bulging, but hard to see at the angle of that photo. I ordered Panasonic FM capacitors from Digikey.ca

I doubt the "bulging" of the transformers is an issue. They usually fail quite silently.

What are the symptoms of your monitor?

[garbermf]

It does not show any signs of power. I did try an ohm meter on both fuse blocks and did not get any continuity. Is this an accurate test on these types of fuses?

[smason]

Originally Posted by garbermf

It does not show any signs of power. I did try an ohm meter on both fuse blocks and did not get any continuity. Is this an accurate test on these types of fuses?

Yes an ohmmeter should be an accurate test of a fuse.
If you post some photos, and point out what/where you tested, we can try to help some more.

[garbermf]

I was testing the two white boxes with an ohm meter. I marked them with red circles with an "X" where the pins are on the back side of the board. I thought these were the fuses.

[garbermf]

Sorry I had to reduce the size of my attachment.

[smason]

Originally Posted by garbermf

I was testing the two white boxes with an ohm meter. I marked them with red circles with an "X" where the pins are on the back side of the board. I thought these were the fuses.

I don't think those are fuses, they're labelled as caps.

The fuse appears to be the round black component that has the amp and voltage rating on it.

[garbermf]

I found the fuse and it was labeled F850. I tested it and it has continuity.

[PlainBill]

Originally Posted by garbermf

I found the fuse and it was labeled F850. I tested it and it has continuity.

"No sign of power" isn't very specific. Have you checked for voltage out of the power supply? Across the leads of the big cap? As has already been suggested, good pictures of the power supply section would be a good way to help us help you.

PlainBill

[garbermf]

Sorry for the delay and thank you for your help.

I measured across the big blue cap and got 368V (ACV).

[garbermf]

PlainBill,
Do you want me to post any pictures back side of the board?