Introduction: How to Fix an LCD Backlight Power Inverter. Using a Fujiplus FP-988D. for $0.

In this instructible i will walk you through fixing a dead lcd back light power inverter using the parts you have. You can tell if you have a dead back light by first eliminating other possibilities. Check monitor on multiple computers. Make sure the indicator light of the monitor turns on and stays on etc.

For this monitor the problem wound up being two capacitors hit with the "capacitor plague" - (look it up on Wikipedia). and a burnt Surface mount resistor. I sourced all parts from junk i was going to throw out. This was a free fix.

Also be careful when working with capacitors and this inverter in general. It is EXTREMELY highvoltage and capable o giving quite a shock. Also to bridge a fuse like i did - is not very smart. Manufactures are really really cheap - so if they bother to put a fuse into a product - its probably for a good reason.

The only camera i have available is my iphone - which is poor and i apologize. Hopefully you can still get the point. I hope this helps some one. New inverter boards are about 65$ and not worth the price. Hell i only paid 180 for the whole minitor 3 years ago.

be safe

~enjoy

Step 1: Prove Its the Back Light

To prove you have a dead back:
1. turn the monitor while attached to a computer.
2. take a strong flashlight and shine it at the screen
3. look to see if you can make out any dim indication of an image.

*** remember that an lcd screen is like a glass pane. Inorder to see images - there must be a source of light to iluminate it.

Step 2: Pull the Monitor Apart

disassemble the monitor:

On this unit there are four screws on the back and a tabs. Pull the screws and pop the thing apart. Dont be a lazy moron - you dont need to use a screw driver to mar the thing up. Instead slowly work around the perimiter with your fingernails. I was able to use folded pieces of paper as wedges. This worked really well. Keep working at it u will get it. DO NOT USE A SCREW DRIVER. you can do it with out marring up the plastic!

Step 3: Get to the Electronics

once the plastic cover is removed from the back - pull off the metal sheilding. Under th sheilding there will mostlikely be two boards. One of them will be the logic board and the other will be the inverter. The logic board will have the monitor imputs - the inverter will have wires leading to the back lights. Mostlikely the wires will be blue/pink.

Step 4: Look at What Is Wrong

On the inverter board look for obvious damage. Burnt traces - cracked components or in my case buldging capacitors. My capacitors were Done.

Step 5: Salvage Compnents

Electronics do not work by "magic".
When somehting is broken there is a reason. 99% of electronics that are thrown out can be fixed or atleast have some good components. Grab an old vcr or tv or even go on craigslsit and grab an old monitor. Find the piece you are missing and replace it.

In my situation the capacitors were dead. they were buldging and obviously messed up. They were 25v@100uF. In general (and i am no electrical engineer - im actually a bioengineer) in situations where capacitors are being used strictly in a power supply fashion - it is ok to increase capacitance. Here i believe the capacitor is being used to steady out the current and kick start the tubes. By increasing capacitance sometimes you are putting more strain on the power supply that must keep the cap topped off - but often manufactures in there never ending quest to cut cost, put the minimum size of everything in their components. So sometimes it is possible to up the capacitance of a cap and actually improve the unit. (reference increasing RAM capacitors on computer mother boards)


The wikipedia article on the capacitor plague is really interesting (for everyone) - read it. I happened to have an old dell power supply laying around and i took parks from it. Your can get parts from anyhting!!!!

I found 25volt capacitors in the power supply with 330uF capacitance. I know i know, >3x the capacitance? well it works...

Step 6: De-solder & Re-solder!

Out with the old and in with the new!

solder away!

remember most modern capacitors are directional! (match the black stripe of the cap up to the marking on the board)

Step 7: It Dose Not Work?!

At this step i put everything back together and pulugged it in. Nothing. What could it be? Turnsout there is a surface mount fuse. from what i have read online SMD fuses account for 90% of inverter board failures. I read this on a forum so i dont know if it is true. To be honest I had no idea these even existed.

On the inverterboard the SMD fuse is labeled 'R1"... Resistor 1? The only marking on this fuse is the letter "P" or maybe the upside-down lower case "d". Either way i searched and searched but could not find the amp value of this fuse.

Step 8: Bridge the Fuse (AT YOUR OWN RISK)

I was frustrated with trying to find the value of the fuse - surface mount components are not well documented - so i did what any self respecting "get-it-done-for-cheap" hacker would do. I bridged the bastard with some wire.

To my defense - the wire i used was extremely small awg. Probably the thickness of a hair. And i reason that the original cause of the fuse failure was the fact that the capicitors - on their way out were losing capacitance and inturn drawing more current from their source. -(that dosent really make sence i know). Your should really use a fuse. I would guess that the fuse was in the 300mili amp range - but this is just a guess

Step 9: Put It Together and Cross Your Fingers

put it all back together. Turn off all external noise and leave the electronics exposed. When u pulg it in smell for smoke! Listen for any noise.

Turn the unit on... is anyhting burning? If not, then success!

Comments

author
remi.serriere made it!(author)2010-07-07

I like the "Yeah... It might be that... Let's bridge that fuse... I don't have a 100uF, not a problem, let's use a 330uF..." I really like that kind of hacks ^^

author
MolecularSandwich made it!(author)2012-10-13

Thanks for the kind words! (I swear there was some logic there)

&& - The LCD still works 4 years later!

author
VictorF6 made it!(author)2015-11-20

On my 32" LCD TV on two Backlight boards fuses marked as 72V 5A.

author
nationofg made it!(author)2014-12-30

thanks for taking the time to enlighten us!

author
zack247 made it!(author)2011-08-12

unfortunately i wasnt so lucky with 3 15" monitors, the inverters are soldered to the power board, and they seem to be the part that failed, even after replacing all the capacitors the backlights still failed to light, but after testing them with the inverter on my laptop (dont say anything i know it wasnt a smart idea) they are indeed functional, but the inverters are shot.
hopefully i have more luck with this tv i got.

author
andys+electronic+stuff made it!(author)2010-09-30

the inverter drives the back lights, its more common for the inverter board to fail, back lights do fail but not so much, if any one is looking for inverter repair service or other plasma lcd tv circuit board repairs, the have a look at this website for more info.

http://www.andyselectronicstuff.co.uk/index.html

author
motogen made it!(author)2010-04-26

i thought fuses are indicated as f or f1 just like on my case  that im working right now,i have here two not working lcd monitors  and the circuitgoinr to he backligths starts on a parts that says f1 and a value that says f 3a/125v so think its a fuse,although it looks like a resistor,i checked it and its says it open using my multi tester

author
qubic made it!(author)2009-12-10

 "If it's not on fire, it's a software problem."

author
purpulhaze made it!(author)2009-03-13

When screen is dim or dark i thought that the back light is bad and needs replacing (not the inverter). I guess by troubleshooting I would will figure out which one it is.

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