Dell 2208WFP backlight issue

[samsonite]

Hello,

I'm trying to repair a Dell 2208WFP LCD monitor. The backlight goes out after turning it on for a couple of seconds. I managed to disassemble it and identified some bulging capacitors on the power board.

However, since this was my first time disassembling a LCD monitor, I accidently pulled one of the ribbon cables out too hard and broke a plastic connector tab holding it in.

Specifically, this is the small ribbon cable that connects to the front bezel menu buttons. The connector tab I broke is colored brown, and seems to hold the ribbon cable in by only friction. Should have probably pushed instead of pulled. Anyway, no amount of glue will help, as the connector tab is small and hopelessly shattered to pieces.

But, I think if I found a replacement, I could snap it back into its holder, and everything would be ok again. I don't suppose any stores would sell this kind of connector separately? It seems to be a common part among all types of LCD monitors, but I don't know how common.

If I can't find it separately, then what is the smallest and cheapest part I can buy that includes it?

btw, the connector is labeled P305 on the PCB board. The white housing is ok. Just the moveable tab part was broken.
Forget to ask, does this connector have a name? It takes 8 leads or pins.

Thanks

[selldoor]

Re: Dell 2208WFP backlight issue

You might get a better response if you post pictures of the relative parts

[samsonite]

Re: Dell 2208WFP backlight issue

Here's a picture of the ribbon, board, and connector.

Ribbon is labelled P-TWO AWM 20861 E221612 150C 60V W-1.
It's the white connector that this ribbon connects to that I'm interested in.
It had some kind of plastic push/pull gate tab around it that broke off and snapped.
Don't know what's it called or how to find a replacement.

I also found a service manual for Dell 2208wfp, but I could not find part P305 on it.
tsimexico.com/tsi/dell/2208wfpfservicemanual080717.pdf

[samsonite]

Re: Dell 2208WFP backlight issue

Picture of the broken tab that holds the ribbon in the connector.
Too bad I don't have a 3D printer. I would make my own.

[Agent24]

Re: Dell 2208WFP backlight issue

FFC (Flat flex cable) receptacle or socket.

Find one with the same pin number and pin pitch (distance between the centre of each pin) and make sure it's surface mount.
Start with this list for example: http://www.digikey.com/product-searc...=0&pageSize=25
Need to know the pin pitch though.


Will be difficult to replace without damaging the board if you do not have a hot air tool though. (Heat gun could work if you are VERY!! careful)


You might be able to jam a piece of cardboard or something in the broken one instead of the clip though.

[samsonite]

Re: Dell 2208WFP backlight issue

Thanks for the link. Some of these look close, as far as the sliding lock mechanism goes, but not the same:
WM10376TR-ND
WM10376CT-ND
WM10376DKR-ND

I don't intend to replace the entire connector, just the sliding lock part.
It looks like I can snap it back in if I had a perfect match.

This is stamped on the PCB board:
632191700P01
PTB-1917 08/08 '07

Any Dell LCD monitor made around 2007-2008 would probably have it.

If I couldn't find the exact connector, I would probably want to find a cheap/junk PCB board
that has the same connector. I guess websites don't sell electronic junk.

[samsonite]

Re: Dell 2208WFP backlight issue

I tried to get a better picture of it. It's really small.

[Agent24]

Re: Dell 2208WFP backlight issue

I don't intend to replace the entire connector, just the sliding lock part.
It looks like I can snap it back in if I had a perfect match.

Yeah, the problem is that's a big if...

I guess websites don't sell electronic junk.

They do if it's eBay and the seller is in Hong Kong


Why not try just putting the cable in, pushing the broken locking tab in, and sticking the whole thing together with a piece of tape or a small drop of breakable glue\wax. Those cables don't typically need a whole lot of force to hold them in the connector so you could probably get away with such a repair.

Personally I would replace it with a new connector but yeah if you don't have the right rework tools that would be hard.

[samsonite]

Re: Dell 2208WFP backlight issue

Yes, tape is my last resort.

Since these were built in 2007-2008, hopefully there should be a ton of Dell LCD monitors dying out by now? Plenty of junk.

[selldoor]

Re: Dell 2208WFP backlight issue

As you have the old clip did you try sticking it together use epoxy not superglue.

If that is a no go then look see how thick the clip part that goes against the
ribbon is and find something the same thickness - credit card?

If its thinner than it looks then on the side of the ribbon without contacts build it up with layers of insulation tape to the thickness insert it then as has been said -tape the whole thing in position or add dabs of removable glue/sealant

[diif]

Re: Dell 2208WFP backlight issue

I've cut bits of plastic to use as a shim when these type of clips have broken. Thin packaging type used it blister packs. I have also tried taping the cable down, but it was holding the cable away from the pins and wasn't making contact. I needed to put a bit of thin foam tape in fron of the connector to raise the tape up before taping down.

[samsonite]

Re: Dell 2208WFP backlight issue

Thanks.
I have a quick question about the PCB board.

Exactly where is the physical connection between the capacitor leads and the board?
Looking at these photos, is the connection only on the bottom layer of the board?

Reason I'm asking, is that when I was trying to solder off a bad cap (C127), I might have torn off a small circular pad around the cap base. The capacitor was stubborn to remove, so I had to use some pliers.

Now, when I try to solder a new capacitor on, the solder doesn't form around the base. I don't know if this is because there is no pad for it to stick to, or if because I'm not using flux.

Kinda worried that the capacitor is not physically connected. It may just have solder hanging off its lead?

[Agent24]

Re: Dell 2208WFP backlight issue

EDIT:
Had another look at the pictures up close and it does look like you may have lifted some of the copper around the lead holes. If you had done the desoldering properly you would not have to use pliers. In fact, it should just fall clean out on an easy single layer board like that.

What were you using for desoldering?

You say you aren't using flux? That wouldn't help though. Your solder should be flux cored, and if not, you would need to add some. Beware some of the flux pens use quite acidic flux which must be cleaned off afterwards. You are better using rosin-cored solder.

Check out this video: https://www.youtube.com/watch?v=IpkkfK937mU for the basics of soldering if you have not done it before or are unsure.


To fix the problem, make a solder bridge (might help to add some wire) and connect to one of the bare points on the same land as the lead to be soldered. Or, you could get new capacitors, cut the leads longer and bend over to one of those points and solder them there instead.

[samsonite]

Re: Dell 2208WFP backlight issue

Thanks, I see it now. There's a small silver dot/circle next to each capacitor pin hole. I didn't realize what it was until now.
That's how the capacitor pin connects to the board circuitry? Wow, I totally missed it. I assumed the connection was through a pad around the pin hole itself.

BTW, all the pins on bottom of this board have been bent inward, making it difficult to desolder. It would have been easier to desolder if they didn't bend the pins. But, I see now that all the pins are being bent toward the circle/connection point, which explains why they bent them in the first place.

Just to add, I have a desoldering iron and a soldering iron. But, I haven't used them in a couple of years, so I'm back to square one.

[samsonite]

Re: Dell 2208WFP backlight issue

Luckily, I took a picture before I desoldered the caps. I missed all 4 points.

[Agent24]

Re: Dell 2208WFP backlight issue

No, you were right the first time. The connection is by way of a pad around the hole, usually.
I must have written a bad\confusing explanation. Sorry.

At a guess I would say those small areas are an extension of the pad to allow for solder to flow more easily around the end of the bent lead section.

When the leads are bent like that, they are trickier to deal with but not impossible. You have several options:

1) Heat the joint and use the soldering iron tip to bend the lead straight while the solder is liquid (not the best idea and can damage the tip or pad if you push too hard)

2) Same as (1) but use a screwdriver or other tool in combination with the iron. Again, you have to be careful and work quickly to avoid overheating or damage.

3) Remove as much solder as possible with desolder braid. This will require good braid and good technique. Then you should be able to *carefully* slide a blade or thin flathead screwdriver between the track and lead and bend it straight.

4) Same as (3) but use a desolder pump\gun (again, technique is important here. You need to remove almost all of the solder to ensure if the lead is still stuck to the trace it is only by a very small and easily broken 'sweat joint'.

5) If they have flattened the lead completely against the pad, you will have to heat and lift at the same time with method (1) or (2).


Another method would be to cut the old part off on the top-side of the board and then desolder the leads afterwards. I do not typically do this as method (3) or (5) works for me, is less hassle and less destructive if I wish to test the removed component later.

[samsonite]

Re: Dell 2208WFP backlight issue

At a guess I would say those small areas are an extension of the pad to allow for solder to flow more easily around the end of the bent lead section.

That makes better sense. Those extended pad areas are used everywhere on all types of components (caps,resistors,diodes,etc...). I have never noticed them before until now.

[Agent24]

Re: Dell 2208WFP backlight issue

Those extended pad areas are used everywhere on all types of components (caps,resistors,diodes,etc...). I have never noticed them before until now.

It is not something that is typically seen as far as I know, usually the pads are a plain circle or sometimes square. I don't actually remember ever working on a board which had pads the style yours has.

[samsonite]

Re: Dell 2208WFP backlight issue

Well, I finished my work and put everything back together. My backlight is now on and working great.
I think I will leave it on for a couple hours to see if it holds or not.

If anyone has the same Dell monitor, this is what I ordered from Digikey:
P12413-ND

This is a Panasonic 330uF 35V aluminum capacitor, FM series.

Bad caps on the board:
C127 = CapXon 330uF 35V, replacement: P12413-ND
C128 = CapXon 330uF 35V, replacement: P12413-ND
C815 = CapXon 330uF 35V, replacement: P12413-ND

Neaby caps that looked good (no replacement):
C129 = CapXon 220uF 35V, replacement: P12411-ND
C812 = CapXon 470uF 35V, replacement: P12415-ND
C825 = CapXon 1000uF 16V, replacement: P12366-ND

Total with shipping was around $11 bucks.

Tools I used:
- Desoldering iron (45-Watt)
- Soldering iron (25-Watt)
- 5mm hex nut driver. This is to unscrew the hex nut pairs around the DVI/VGA ports if they can't be removed by hand.

Tools I didn't have but should have used:
- Pry/Spudger tool. This is a very thin, flat plastic tool to open up the monitor case. I used a flat screwdriver instead, and destroyed about half the plastic tabs inside the bevel frame. The tabs were very thin and fragile, almost as if they were made to be tamper proof. Makes me think the monitor wasn't designed to be opened after it was sealed.

This saved me about $300 bucks for a new monitor. I hope it will last another 7-8 years, but I figure the CCFL bulbs will be the next to go if the caps don't go first.

Thanks for the help!

[Agent24]

Re: Dell 2208WFP backlight issue

Good to hear you got it working!

Although I would advise you replace the other CapXon capacitors as they are a very low quality brand and visual appearance alone cannot always determine condition. The only way to know for sure is to test ESR and Capacitance with the appropriate equipment.

Without such test equipment, it's always advisable to replace the lot, especially if the capacitors are a known crap brand, and\or there are already some failures of the same brand in the device.

Also, replacing the PSU capacitors means the ones on the mainboard should last longer, and those are more difficult to replace given that they're on a multilayer board.