Gateway FPD2185W

[PlainBill]

Re: Gateway FPD2185W

Yeah, I'm just figuring that out now; I've been doing motherboards for awhile now, and on so many laptops where the screen doesn't work its a bad connection to the bulb - so I'd gotten used to looking for that. Recently I started doing LCD monitors and Flat-Panel TV's (funny how people will pay more to fix their TV then their computer isn't it?) and haven't really done enough homework on the basic circuit theory. I was referring to a pair of Acer monitor schematics when I noticed the 5 to 1 thing.

Do you have, or can you point me to some basic reference schema for the protection side of it? I understand how the pwm chip feeds switching fets into transformer, just a little fuzzy on the sensing of over voltage and over current. I have attached one of the schema's I'm working with, do most multiple tube backlights implement the over voltage with a string of transistors like this one (Q502-Q505) - looks like all 4 co-operate to hold Q501 off right? And when Q501 turns on by the pull up resistor it trips the protection?

The bottom edge of the schematic is cropped; something is missing. I've seen this before; just can't remember where or when.

OVP is simple. R501 and R502 form a resistive voltage divider. The positive peaks are transferred to OVP1 by D508 pins 3 and 2. C527 and C530 form a capacitive voltage divider. D507 pins 3 and 2 transfer the positive peaks. And of course the same circuit is present for the other pair of CCFLs. C507 is charged to the level of the highest peak; if it goes too high the inverter controller is shut down.

Current sense is handled similarly. I've never been able to get my head around this over current protection scheme. This design is quite rare.

PlainBill

[PlainBill]

Re: Gateway FPD2185W

Yeah, I'm just figuring that out now; I've been doing motherboards for awhile now, and on so many laptops where the screen doesn't work its a bad connection to the bulb - so I'd gotten used to looking for that. Recently I started doing LCD monitors and Flat-Panel TV's (funny how people will pay more to fix their TV then their computer isn't it?) and haven't really done enough homework on the basic circuit theory. I was referring to a pair of Acer monitor schematics when I noticed the 5 to 1 thing.

Do you have, or can you point me to some basic reference schema for the protection side of it? I understand how the pwm chip feeds switching fets into transformer, just a little fuzzy on the sensing of over voltage and over current. I have attached one of the schema's I'm working with, do most multiple tube backlights implement the over voltage with a string of transistors like this one (Q502-Q505) - looks like all 4 co-operate to hold Q501 off right? And when Q501 turns on by the pull up resistor it trips the protection?

You are correct, the Q502-Q505 work together to hold Q501 off. When any of them turn off, Q501 turns on, tripping the protection. This design is unusual, but works because of how the OZ9910G works. At turn-on the output drive is ramped up slowly (soft start). During this time the ISEN (current sense input is ignored). As the lamps start conducting, Q502 - Q505 turn on, turning Q501 off, and the controller enters it's run phase. The OX9910G datasheet here gives more information.

PlainBill

[TheHarbinger]

Re: Gateway FPD2185W

I just picked one of these up and thought it might be an easy fix, thanks to the great info in this forum. I replaced all the electrolytics with the preferred DigiKey Panasonic units, and although the MOSFETs looked okay with no board discoloration I replaced those as well.

I still got the faint 'sizzling' sounds and the 'several seconds to black.' I reopened the monitor and decided to reflow the connections. I've never seen so many crappy solder joints on a board! The big thing I noticed was that, after sucking some of the bad connections clean and resoldering with a good 60/40 solder, the joints would still cool too quickly and look cold. Weird. I had to rework some of the bigger connections and heat them for a much longer time to get halfway-good looking connections. I have an adjustable-heat electronic-type iron, and I tried lower settings (longer to heat) and higher settings (faster heating but faster cooling as well) with no real difference.

After this, I still get the blackout problem but it takes 6-8 seconds. Also, I see a number of thin, vertical lines on the display when its displaying a PC image on the DVI input (before it blacks out, that is). I haven't yet tried the other inputs. I'd try to take a picture but I think the display would blank out before I could get everything set.

I'm hoping the actual panel isn't shot; when its first powered on and I get the Gateway logo I don't see those lines. Could this be, perhaps, bad joints on the input/output board?

BTW, I will reopen the thing again and reflow more joints on the inverter/PS board. I also plan to open the panel to check the lamps, but I'm not looking forward to that task...

[TheHarbinger]

Re: Gateway FPD2185W

Also, I see a number of thin, vertical lines on the display when its displaying a PC image on the DVI input (before it blacks out, that is).

I should add that those lines are reminiscent of what you'd see if some columns in the panel were bad. I'm not convinced that's the problem, though.

[TheHarbinger]

Re: Gateway FPD2185W

An update and a question.

I parked this monitor for a while and went back to it last night. I'd pulled a set of fluorescents off another display that were good (but the LCD was cracked) to use for testing. To remind myself of the exact problem I powered up the FPD2185W.
- I could hear some distinct but faint sizzling sounds coming from the bottom edge of the LCD panel.
-The monitor would power up for approximately 8 seconds before the backlights turned off.

The spare backlights I'd pulled all had 2-pin connectors, and I realized that one set of lights for the top and bottom edges of the LCD had 5-pin connectors. I knew I couldn't test them all, but just as a what-the-hell gesture I unplugged the single bottom-edge 2-pin connector from the main PC board (as you look at the board with the LCD connectors on the right, this would be the bottom-most connector) and plugged one of the test lights in its place. I then powered up the monitor again.

Interesting find: the external light stayed on for about 8 seconds before going off with the others, but the sizzling sound moved from the light(s) inside the LCD's bottom edge to the external light. I could place my ear to the bottom of the panel and hear no noise; when I held the external light to my ear I heard the sizzling sound. I tested this with the other three spare lights, all with the same results.

So would it be safe to say that the problem in this case wouldn't be with the backlights themselves but is still with the inverter board?

[TheHarbinger]

Re: Gateway FPD2185W

An update and a question.

I parked this monitor for a while and went back to it last night. I'd pulled a set of fluorescents off another display that were good (but the LCD was cracked) to use for testing. To remind myself of the exact problem I powered up the FPD2185W.
- I could hear some distinct but faint sizzling sounds coming from the bottom edge of the LCD panel.
-The monitor would power up for approximately 8 seconds before the backlights turned off.

The spare backlights I'd pulled all had 2-pin connectors, and I realized that one set of lights for the top and bottom edges of the LCD had 5-pin connectors. I knew I couldn't test them all, but just as a what-the-hell gesture I unplugged the single bottom-edge 2-pin connector from the main PC board (as you look at the board with the LCD connectors on the right, this would be the bottom-most connector) and plugged one of the test lights in its place. I then powered up the monitor again.

Interesting find: the external light stayed on for about 8 seconds before going off with the others, but the sizzling sound moved from the light(s) inside the LCD's bottom edge to the external light. I could place my ear to the bottom of the panel and hear no noise; when I held the external light to my ear I heard the sizzling sound. I tested this with the other three spare lights, all with the same results.

So would it be safe to say that the problem in this case wouldn't be with the backlights themselves but is still with the inverter board?

Anyone?

[alexanna]

Re: Gateway FPD2185W

Anyone?

I would still suspect a problem with one of the CCFLs wiring inside the panel.
Take a picture of the CCFL pig tails, so you remember the wiring original positions.
And then remove the wiring and terminals from the plastic housings. Then position the known good bulbs and wiring into the connectors that fit into the monitor you're trying to diagnose.
If you don't know how to remove the wiring from the plastic connectors, post a picture of them and I will talk you through it.

[baysailor]

Re: Gateway FPD2185W

Hi,
I am not an electronics person, but am fairly handy, I replaced 8 capacitors on my Gateway Fpd2185w a few years ago. It died suddenly while using it yesterday. From what I have read here it seems I have the 2 seconds to black problem. I don't have access to any ccfls that I could test the bulbs with. I was wondering if I take the monitor apart so I can see the lamps, would I be able to visually tell if a bulb was bad by turning the monitor on and watching them? Each time I turn the monitor on, the Gateway logo comes up, then the screen goes blank. Shortly after that the power light goes to orange unless I have the computer connect to it running, in which case the power light stays blue.

I do have a few multitesters laying around. Any help would be appreciated.
Thank you.

[2dfx]

Re: Gateway FPD2185W

Hi,
I am not an electronics person, but am fairly handy, I replaced 8 capacitors on my Gateway Fpd2185w a few years ago. It died suddenly while using it yesterday. From what I have read here it seems I have the 2 seconds to black problem. I don't have access to any ccfls that I could test the bulbs with. I was wondering if I take the monitor apart so I can see the lamps, would I be able to visually tell if a bulb was bad by turning the monitor on and watching them? Each time I turn the monitor on, the Gateway logo comes up, then the screen goes blank. Shortly after that the power light goes to orange unless I have the computer connect to it running, in which case the power light stays blue.

I do have a few multitesters laying around. Any help would be appreciated.
Thank you.

Chiming in here as a first timer with the same problem, except my 2185's on time varies between 2 seconds and 5 seconds. I get a clear picture, but the panel eventually shuts off. Recapped the board to no effect. I have the 4 driver transistors sitting on my desk that I ordered with my digi-key capacitor order that I haven't installed yet because I have very little experience with surface-mount style components. The caps were easy because they're all through-hole.

[retiredcaps]

Re: Gateway FPD2185W

2 seconds to black can be

a) bad caps
b) bad ccfls and/or wiring
c) bad inverter transformer

All the above (and more) discussed starting with posts #13 and #14 at

https://www.badcaps.net/forum/showthread.php?t=10419

Also note the misc suggestion #1 on how to attach your pictures.

[jayoung]

Re: Gateway FPD2185W

Hi,
I don't have access to any ccfls that I could test the bulbs with. I was wondering if I take the monitor apart so I can see the lamps, would I be able to visually tell if a bulb was bad by turning the monitor on and watching them? .

You would need to take the monitor apart and then probably disassemble the lcd panel to expose the ccfl's (exception is that sometimes the ccfl's "slide" out from the lcd panel). This can be difficult if it's your first time. Make sure you have plenty of space to lay out each part of the panel. You need to be able to remember the order and orientation of each part when re-assembling. The most common issue that I have seen with ccfl's is the wires connected to the ends sometimes "burn" off and need to be re-soldered. If the ends of the ccfl's are dark, they may be nearing or at the end of their life. Ccfl's can also be cracked.

[baysailor]

Re: Gateway FPD2185W

Ok, I will take the monitor apart, I have not pulled the Lcd apart before, but I am used to pulling things apart and putting them back together, including laptops that I have replaced parts inside to get them up and running again. I am just a bit clueless when it comes to testing a piece on a board, I don't know what can be tested in circuit, or has to be pulled. I will look for the burnt wires/dark ends on the tubes. I can buy a ccfl to use to test with, but was hoping that if I could turn it on while being able to observe the tubes, I might see that one did not light properly, before it shuts off.

Retiredcaps, I have been reading the posts you suggested and will also try and do some testing, thanks.

Thanks

[jetadm123]

Re: Gateway FPD2185W

Hi,
I am not an electronics person, but am fairly handy, I replaced 8 capacitors on my Gateway Fpd2185w a few years ago. It died suddenly while using it yesterday. From what I have read here it seems I have the 2 seconds to black problem. I don't have access to any ccfls that I could test the bulbs with. I was wondering if I take the monitor apart so I can see the lamps, would I be able to visually tell if a bulb was bad by turning the monitor on and watching them? Each time I turn the monitor on, the Gateway logo comes up, then the screen goes blank. Shortly after that the power light goes to orange unless I have the computer connect to it running, in which case the power light stays blue.

I do have a few multitesters laying around. Any help would be appreciated.
Thank you.

Just out of curiosity, what brand/series of caps did you use for the initial repair?

[baysailor]

Re: Gateway FPD2185W

Back when I did the repair, the website I read about it gave the Radio Shack part number. I did not pay attention to the brand, to tell the truth. Back then there seemed to be a lot less information on my monitor than there is now.

[jetadm123]

Re: Gateway FPD2185W

Back when I did the repair, the website I read about it gave the Radio Shack part number. I did not pay attention to the brand, to tell the truth. Back then there seemed to be a lot less information on my monitor than there is now.

Radio Shack does not sell low-esr caps, which is what you need to perform a proper repair. Suggest you first try recapping with something like Panasonic FM, FR or FC caps. Use digikey.com, choose USPS first class shipping for lowest cost shipping.

[baysailor]

Re: Gateway FPD2185W

I found a kit of capacitors for the FPD2185W that has the capacitors for the power and logic board for under $13, including shipping. The capacitors are all NCC except one is Rubycon. The capacitors I put into the monitor from Radio Shack are Xircon. Are NCC capacitors ok?

[2dfx]

Re: Gateway FPD2185W

Okay, so I recapped my board with Panasonic FC caps, and used Panasonic EE for the big filter caps. No change, except it displays a picture for maybe 1 second longer depending on how temperamental it's feeling.



Here is the bottom of the board showing the transistors:



And here are the multimeter measurements of said transistors. They were measured with the 20k range:

Pin - 1-2 | 1-3 | 2-3
---------------------
U301 OL  4.79k OL
U302 OL  OL   OL
U304 OL  4.79k OL
U305 OL  OL   OL

[jetadm123]

Re: Gateway FPD2185W

I found a kit of capacitors for the FPD2185W that has the capacitors for the power and logic board for under $13, including shipping. The capacitors are all NCC except one is Rubycon. The capacitors I put into the monitor from Radio Shack are Xircon. Are NCC capacitors ok?

NCC (Nippon Chemicon) is the same as United Chemicon. If they are one of the series listed in the following link, then you should be fine:

https://www.badcaps.net/forum/showthread.php?t=2280

[baysailor]

Re: Gateway FPD2185W

All the caps in the kit are approved series except that the Rubycon series is YXF.

[TheHarbinger]

Re: Gateway FPD2185W

An update and a question.

I parked this monitor for a while and went back to it last night. I'd pulled a set of fluorescents off another display that were good (but the LCD was cracked) to use for testing. To remind myself of the exact problem I powered up the FPD2185W.
- I could hear some distinct but faint sizzling sounds coming from the bottom edge of the LCD panel.
-The monitor would power up for approximately 8 seconds before the backlights turned off.

The spare backlights I'd pulled all had 2-pin connectors, and I realized that one set of lights for the top and bottom edges of the LCD had 5-pin connectors. I knew I couldn't test them all, but just as a what-the-hell gesture I unplugged the single bottom-edge 2-pin connector from the main PC board (as you look at the board with the LCD connectors on the right, this would be the bottom-most connector) and plugged one of the test lights in its place. I then powered up the monitor again.

Interesting find: the external light stayed on for about 8 seconds before going off with the others, but the sizzling sound moved from the light(s) inside the LCD's bottom edge to the external light. I could place my ear to the bottom of the panel and hear no noise; when I held the external light to my ear I heard the sizzling sound. I tested this with the other three spare lights, all with the same results.

So would it be safe to say that the problem in this case wouldn't be with the backlights themselves but is still with the inverter board?

Postscript to this botched affair...

I took some other advice in this thread and finally disassembled the panel itself. (Note to anyone disassembling an LCD panel: make sure that when you pull out the plastic sheets between the LCD itself and the thick, clear lightboard material that you pull them all off at once, keep them together, and note which way you pulled them off and which side faces the back of the panel.) Two of the three tubes in the bottom CCFL strip had blackened ends; additionally, one of the return wires was blackened near the solder point and snapped off easily. One of the other wires wasn't black but it also came off easily.

I ordered three new tubes and, while I was waiting, tried pulling the silicone caps off. On the return wire end the cap was "stuck," probably partially melted. It ripped into several pieces when I tried pulling it off. I also ordered eight 3-tube silicone end caps from CCFL Warehouse that weren't an exact fit and had to be trimmed to fit. Good thing I ordered eight--I mis-cut five of them. That silicone material is hard to cut even with a new and sharp X-acto blade. When the tubes arrived I repaired and reassembled the bottom tube strip then put the panel back together. In my earlier post I'd mentioned that the panel, when it was on, would display some vertical colored columns of apparently dead pixels. This I guessed was due to bad connections from the thin mylar panel connectors that were glued to the controller board on back of the panel assembly. When I tested the panel I saw a lot more of those, as well as a scrambled picture on the panel. I gently reheated each mylar connection point with a hair dryer and carefully burnished the connection with a flexible plastic wand used for applying rub-on lettering.

When I powered the panel up again I got a very faint scrambled picture, lots of lines, nothing recognizable. I lifted the panel itself off the lightbox and saw lots of flourescent light behind it, so the backlight problem was fixed. However, the panel itself seems to now be toast.

I learned some things when doing this one (as well as accidentally destroying the panel on a 22" Viewsonic LCD HDTV I was also working on at the time). If I find another unit of either model I may try this again, but for now I think I'll stay away from disassembling panels. If it's cap related I know I can do it. The panels themselves require a steady hand and some special joojoo to repair and I apparently don't have any of it...