Broken Dell 1800FP Power Supply - when and when not to resolder?

**PlainBill** · 04-29-2009, 10:10 PM

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

The browning around D903 and D906 appears to be flux. Components with heat sinks present a problem in manufacturing. The heat sink must be attached when the component is soldered of it won't be at the right height. But heat sinks interfere with the wave solder process, so these are often hand soldered afterward. And sometimes someone doesn't bother removing the flux.

None of the joints on D903 look particularly healthy. And given what you (probably) got ripped off for the directions, you might as well resolder every one of the pins mentioned. Even if it takes you 2 minutes a pin, it's a quick job.

I've attached a touched up picture indicating the separate areas. Mainly you are concerned about the leads of D903, etc.

NOW, the facts of life. Just because poor solder joints on T901 and D903 and D906 are a common cause of failures on these power supplies doesn't mean that they are the ONLY cause of failure.

PlainBill

Attached Files

**Bobdee** · 04-30-2009, 02:54 AM

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

Originally posted by maverick530

I own a Dell 1800FP whose Power supply (LG part #:6870T445D10 2003.05.07) is bad. I know this because I have replaced it with a known good power supply and the monitor works fine. I want to fix the power supply so I can have 2 monitors.

1st, I purchased fix it instructions that say to resolder the transistor connections at T901, but my connections there look stellar (perfect). Do you think I can skip this step?

2nd, upon visual inspection of D903, I'm not sure which sections should connect to each other after I'm done. Should just A&B be touching with solder? or just A or what? How does one know without a schematic? Could the browning between the top 3 connections be shorting out the cirucuit?

3rd, there's a lot of other browning on the board (not listed in the instructions of things to resolder) where it looks like the solder got runny. Might these need to be "resoldered" as well?

Thanks for any and all help,

Hello Maverick
This Schematic will help you and Plainbill sort your problem out with luck, Its not for your monitor but its your p/suppy to a T.
Also my problems with FP1800 was,
AC input fuse, 0.33 resistor (R923), Mosfet on H/sink that resistor goes to, and power controller ICE2AS01, along with a lot of bad solder joints, particulary the diodes on H/sink that you mention, this may help you,

bob

**Bobdee** · 04-30-2009, 03:32 AM

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

Sorry lads messed up somwhere with above link, will try again,

cant understand why other link dont come up,
bob

**PlainBill** · 04-30-2009, 06:24 AM

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

Bobdee, thank you very much. I almost cried when I saw the manual - Actual Schematics!!!!

PlainBill

**maverick530** · 05-03-2009, 05:27 PM

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

Thanks so much PlainBill and Bobdee,

I resoldered all the places on the instructions (better safe than sorry), as well as a few other places that just looked bad, and replaced the IC (see attachment 1).

Plugged the power supply back in and the LCD turned right on! Success!

Also attached is a before and after shot of D906. Does it look cleaner to anyone? I wonder if simply replacing the IC does the trick or if you really have to re-solder all these since they don't exactly LOOK much better.

Attached Files

**Bobdee** · 05-04-2009, 01:43 PM

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

Congrats on the Dell fix, good job, nice one
bob

How did the Benq FP767 go after ???
Have you finished that one yet ???

**stephenshane** · 08-11-2009, 02:09 PM

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

This thread was helpful. $12.00 spent for a monitor and parts and I was able to gain approx 2 square feet of desk space.

Thanks
Stephen

**akmo512** · 12-08-2009, 05:26 PM

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

The dell 1800FP , allot of faulty PB! The fix is simple.
After removing your faulty power board flip it upside down,under there you will see the diagram for the 8 wires (2) Gounds) pair them (2) 12.volts)pair them (2) more Grounds)pair them and (2) 5.volts) pair them.

lucky for you these 8 wires make 4 pairs LOL

Take the 4 wires in the right order plug them into a molex connector(computer power supply)you could use your pcs power supply if you have 50 watts to spare just extend your 4 wires and hook them in the proper order to your molex connector.

I added a dell pc computer supply to the back of this lcd and it runs perfect
just mod the powersupply by creating a bridge I think its the 4th and 6th to have it turn on w/o a pc.

So if your stuck w/o cash like me,but wanna fix this lcd w/no extra parts!
DO IT NOW
Things to Know Pair the wires in order!
Research Color voltage for a Molex!
Be careful caps store electricity!

**nep58** · 12-31-2009, 10:18 AM

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

I will be changing a few caps on the PS and while I was at it, was going to change the L901 and L902 parts. They seem to be inductors but besides 3.3uH, I can't find any info about them to order replacements. Any help would be appreciated!
Thanks

**PlainBill** · 12-31-2009, 11:35 AM

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

Originally posted by nep58

I will be changing a few caps on the PS and while I was at it, was going to change the L901 and L902 parts. They seem to be inductors but besides 3.3uH, I can't find any info about them to order replacements. Any help would be appreciated!
Thanks

Don't bother replacing the inductors. They are very unlikely to fail. All it is is a length of heavy gauge wire around a ferrite core, for Faraday's sake!!! (Question: If Faraday discovered electromagnetic inductance, why is his name used to denote capacitance. And who was this Henry guy?)

PlainBill

**nep58** · 01-09-2010, 02:58 PM

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

Thanks PlainBill!
The problem that I had with my 1800FP was that from one day to the next, it went totally dark. No power light at all, nothing on screen, seemingly totally dead. I changed the ICE2AS01 chip which didn't fix the problem. Output voltages were the double of what they were supposed to be. I decided to change ALL of the radial caps on the PS (9) and LB (4) for a whopping $10. Problem fixed!

**PlainBill** · 01-09-2010, 04:53 PM

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

Originally posted by nep58

Thanks PlainBill!
The problem that I had with my 1800FP was that from one day to the next, it went totally dark. No power light at all, nothing on screen, seemingly totally dead. I changed the ICE2AS01 chip which didn't fix the problem. Output voltages were the double of what they were supposed to be. I decided to change ALL of the radial caps on the PS (9) and LB (4) for a whopping $10. Problem fixed!

Makes you feel good, doesn't it!!!

PlainBill

**USAFJohnson** · 01-20-2010, 11:34 AM

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

Hey everyone,

I am an electronics tech in the Air Force and came across one of these monitors (1800FP), Someone brought it to my workcenter for possible repair. It was on it's way to the big AF dumpster in the sky DRMO. It came in with no power indications (nothing). Went through basic steps, different power source, cables, fuses, etc. I read all your posts and got it down to the ICE2AS01. We had one in our shop stock, replaced it and tighted up all the factory solder globs and its out the door good as new. You guys rock! Thanks for all the good info, keep it up.

USAFJohnson

**akmo512** · 02-23-2010, 05:19 AM

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

Wanted to do a follow up I Still have the 1800FP running on the molex connector of a power supply.

Actually disconnected mounted power supply and ran an extension to pc runing it off the power supply on the pc it already had the physical vga cable , no sacrifice by being one more string attatched

Allso If you are pulling this off make sure you dont have a very power hungry video card.

DIAGRAMS ON BOARD - get that FAULTY Power supply out and fix it for free

**disbecknell** · 08-05-2010, 12:09 PM

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

After reading this forum, I finally opened up my 1800FP to see if I can fix it. My problem seems a bit different, and maybe less serious. The monitor will turn on (power led lights up), but the screen stays black. For a while, all I had to do was wait til it had been running an hour or so and warmed up, and then poof, the screen would come on after flickering for a few minutes. After I lived with that for awhile, it wouldn't come on at all unless I draped a blanket over the entire thing to really warm it up. Then it would work for hours, until I guess it cooled off and went dark again. My thinking is that there's a bad connection that, once hot and expanded, works.

I removed the power supply board and visually inspected the solder joints... a few look like they could be cleaned up but there's no clear breaks or burns. Does this sound like a PS problem, or should I be looking somewhere else? If no responses soon I'll probably just clean up the obviously bad solders and see if that fixes it.

**mockingbird** · 08-05-2010, 12:29 PM

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

And sometimes someone doesn't bother removing the flux

Wait.... flux is CONDUCTIVE??!?!?!??

(maybe that's why the last two LCD repairs I have attempted failed)

**retiredcaps** · 08-05-2010, 12:39 PM

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

Originally posted by disbecknell

n at all unless I draped a blanket over the entire thing to really warm it up.

If no responses soon I'll probably just clean up the obviously bad solders and see if that fixes it.

A hair dryer would be better than a blanket catching on fire.

Yes, resolder the joints and see if that helps.

**Toasty** · 08-05-2010, 12:54 PM

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

Originally posted by mockingbird

Wait.... flux is CONDUCTIVE??!?!?!??

(maybe that's why the last two LCD repairs I have attempted failed)

Where did you get that quote from?? Not on this page.

Flux is not conductive.

**gregsal** · 10-05-2010, 06:53 PM

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

Originally posted by PlainBill

Bobdee, thank you very much. I almost cried when I saw the manual - Actual Schematics!!!!

PlainBill

I couldn't have said it better! I have about 4 of these power supplies to fix.

I'm the "swollen capacitor guru" at work, but the cold solder joints and IC 901 were kicking my butt on a couple of them.
Apparently LG had a very consistent manufacturing process on these power supplies - they all fail the same way!

I repeat "ACTUAL SCHEMATICS!!!" - and a parts list! AWESOME!

Thank you!

gregsal

Broken Dell 1800FP Power Supply - when and when not to resolder?

Broken Dell 1800FP Power Supply - when and when not to resolder?

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