Any ideas on how to properly test voltage on the LCD inverter input and output?
My Satellite 5105-S701 fails to light the backlight. I can see the image when using a flashlight and the image on an external monitor is fine. I tested the output from the inverter board and am getting zero volts. The input has many fine wires and without a pinout I have no idea how to test for voltage going into the inverter. I took it to a laptop repair place and told them I thought it had a bad inverter and would they please diagnose it for me. I guess I was too specific because when I picked it up they simply told me the inverter was OK and handed it back to me with the backlight still not working and no idea why it’s not working.
Any ideas on how to properly test the inverter input and output? I would try a known good inverter but I don’t have one. Any other suggestions as to why the backlight won’t light? Or any other tests I can run? I’ve found all the software backlight controls and they’re all cranked up. Thanks for any help!
That’s a question I keep asking myself over and over. How can I test an FL inverter board using just a multimeter? Unfortunately, I do not have any straight answer at this time. I believe that you can measure the voltage on the input if you connect the positive probe to the pin 1 on the FL inverter and the negative probe to the laptop chassis. The multimeter should be set to test DC voltage. I think that the voltage on the input could be somewhere between 9-30VDC, just in case set the multimeter to a higher voltage. The pin 1 on the FL inverter board should be marked; I’ve seen it marked before. You should get some voltage on the inverter input. If you get zero volts on the input, then it’s possible that cable is bad or the connection on the system board is bad. Now about the output voltage. I believe that you can get an accurate readings on the FL inverter board output only if it’s loaded properly, in other words if the backlight bulb is connected and it’s in a good working condition. It could be a very high AC voltage. I would set the multimeter to at least 1000VAC. Be careful, it’s a very high voltage and if you do something wrong and short a circuit, you can permanently damage the laptop. Sorry, but I cannot provide more specific information. If you find any info on how to test a failed backlight with a multimeter, please let me know.
Usually, when I have a problem with the backlight, I unplug the screen and connect my test backlight bulb. If it lights up fine, then the backlight in the LCD screen is defective. If it doesn’t light either, then most likely it’s the FL inverter board fault. Video cables do not fail very often.
June 16th, 2010 at 7:32 pm
i have a ze4610us i replaced the lcd inverter 4 times and not working, cn1 is pin1-0 pin2-5.11 pin3-3.31 pin4-3.73 pin5-0 ant one know were on the we i can find out what the pin input volts are?
May 18th, 2010 at 3:25 pm
OK, I solved my own problem… sort of. The bottom line was that the logic board was NOT outputting any voltage for the “dim control” input to the Inverter board. According to some other info found on the Internet, the “dim control” pin should have a voltage ranging from 0 to +4 volts depending on the dimming desired (where 0V = no light, 4V = max light). Since the logic board wasn’t outputting any voltage on that pin, the backlight remained off. So, since I had no intention of buying a new logic board for such an old computer, I decided to just manually put +4V on the pin. Here’s how I did it…
First off, the CORRECT pin names and voltages to the input connector of the Inverter board are here (again, this is for Powerbook G4 17″ Aluminum). This is slightly different than what I wrote in my original message…
CHASSIS GROUND – Green wire (connector pin 1): Hardwired to chassis ground
+12V SUPPLY – Black wire (connector pin 2): +12V
CABLE GROUND – Gray wire (connector pin 3): 0V
+5V SUPPLY – Blue wire (connector pin 4): +5V
DIM CONTROL/ENABLE – Silver wire (connector pin 5): 0 to +4V depending on dimming
So, it was the DIM CONTROL that was dead from the logic board. I had both 12v and 5v available to me at the input connector to the Inverter board so, at first I figured I’d just connect the 5v to DIM CONTROL. At first it worked but, after about 1 minute, the backlight would shut off, presumably because the Inverter was being “overdriven” and it has some kind of overcurrent shutdown circuitry. So, I went to plan B and, though experimentation, found that a 3K ohm resistor placed between pin 4 and pin 5 brought the voltage on the DIM CONTROL to +3.8V which kept the backlight bright without it shutting down. See pictures below.
Now, for the bad news. Not only will the screen not dim (which I can live with), but it also won’t shutoff when going into sleep mode (the display goes away, but the backlight remains lit). For the record, it DOES shutoff when the computer is ShutDown. But, this poses yet another challenge. Since I generally only use my computer from home while it is plugged in, I may not worry about this one for now. But, for many people, this might be a showstopper. None the less, I did get the backlight working.
John
http://www.djjohnnymac.com/images/IMG_4329.jpg
http://www.djjohnnymac.com/images/IMG_4330.jpg
http://www.djjohnnymac.com/images/IMG_4331.jpg
May 13th, 2010 at 8:35 am
Dead LCD Backlight on Mac Powerbook G4 Aluminum 17″…
OK, so I’m pretty handy with my Powerbook. In the past, I’ve replaced 2 different hard drives, a DVD-R drive and a few other things. In short, I’ve torn my Mac apart and put it back together successfully on numerous occasions. By this latest problem has really stumped me. I’ve read up on everything I can find on the Internet and changed out many parts, but still my LCD backlight is dead. Here is what I’ve done so far…
1) First, I assumed it was the Inverter board, so I ordered a replacement, opened up the screen (man, that was a bear) and installed it. Still, no backlight.
2) Next, assumed it was the inverter cable. Repeated above process with new cable. No light. But old cable was damaged (one wire broken), so it seemed like that was a clue. But still no light with new cable.
3) Next, assumed it might be the backlight itself, so I ordered one (complete with compatible 2-pin connector so no soldering needed). I didn’t actually install it (which is an even bigger bear than lid removal), but I did plug it into the inverter output to test it out and… you guessed it… no love.
4) I figured that somewhere along the way, I burned out the replacement inverter board that I bought (OK, I put a meter across the outputs). So I bought ANOTHER replacement inverter. Plugged it in, powered it up… still no backlight (I tried it first with the new replacement bulb just in case original bulb was shorted out).
I have since tested the outputs of the Inverter using the “new Morris Rosenthal technique” outlined in this article above (Harbor Freight meter on kHz setting and probes an inch or so away acting as antennas). When I do that, I get no frequency reading at all on the meter (0 kHz). But, as he said, maybe this is a high frequency inverter and the meter can’t sense frequencies that high.
At this point, I am completely stumped. I checked the input voltages to the inverter board and the seem OK, although I can’t find anything on the Internet that states exactly what they should be. But they aren’t zero (at least not all of them). Here’s what they are…
Silver wire (pin 1, perhaps): 0V
Blue wire (2): +5V
Gray wire (3): 0V
Black wire (4): +12V
Green wire (5): hardwired to ground
So, I’m in for about 90 bucks so far in parts and the thing is still dead. Oh yeah and, by the way, I know it’s the backlight because I can see faint images on the screen AND the laptop works fine when connected to an external monitor. I already have a newer MacBook Pro that I use for everyday stuff, but it would really be nice to get the old G4 working again. Anyone have any suggestions about where to go from here?
John
April 20th, 2010 at 12:27 am
I think all of them written the input voltages of inverter. i need to know about the output of the inverter which is going to the inverter on two wires ( Red and White).
what are voltages available on those pins.
Thank You
March 29th, 2010 at 2:10 am
my acer aspire 4720
In my case I connected the “+” lead of the multimeter to the pin 1 on the connector and the “-” lead to the ground trace around the screw hole don’t output 19 volt but the cable is ok.what testing in dhe board?
March 20th, 2010 at 9:31 am
So, heres whats up. I work at a mom ‘n’ pop style computer repair center, and i made an interesting discovery too. We have had a few Dell Inspiron 1525 inverter replacement issues. The 1525 model is prone to inverter failure, but what sucks more, is that when you put the new inverter in, you loose much control over the dim level. its not a compatability issue, it’s a domestic issue. Almost as if the new inverter is a replacement organ, and the body is rejecting it.
Now, this comes right back to “What’s the pinout?” and the answer to that is, YOU STILL HAVE TO SEARCH FURTHER!!
honestly, it seems as if the consumer is NOT allowed to know the inner workings of their own laptop screen. BUT, i bought a bunch of cheapy inverters, that are only 4-pin, AND come with a 6″ harness. So, with a 110ohm resister on the dim level pin, and +5VDC on the power and control pin, with the ground connected to the chasis, I’v been snaking the wires down through the hindges, and soldering them to the USB jack for my +5VDC power. granted, there is now a breif moment when the system turns on, and off, where the LCD turns off, but the inverter is still on, resulting in a blank white screen for aprox. 1/2 second.
There, theres your dim screen solution.
HAVE FUN!
November 13th, 2009 at 4:47 pm
For testing inverter, check out this link…. it could save you a lot of time and hassle!!http://www.fonerbooks.com/test.htm
June 3rd, 2009 at 1:08 pm
Hey Everybody,
I had the same issue about measuring the inverter output, but I found out that if you measure in paralell to the inverter exit you will get no reading, I’m guessing the inverter can’t take much Amps, I tried measuring on a working laptop and when I tried to measure the voltage the whole screen whent dim, I had to shut it down and then turn it back on to have the screen light up ok.
On the bad laptop I just bought the backlight that I’m guessing is what’s wrong with it.
hope this helps anyone!
March 31st, 2009 at 9:09 am
Hi,
I trapped one of the 7 wires running from my laptop motherboard to the inverter and it shorted out, my screen is on but with a dim image using AC power. I checked the inverter was working with an old CCFL. I got a bright picture back by touching Pin1 to Pin4 but on battery is was back to a dim picture (Accidently touching Pin1 to Pin3 made a spark and turned the screen off completely) Turning the notebook on I am now back to a dim picture, I took readings before and after the event -
Before (Dim Picture) Pin1 7.12v; Pin2 7.12v; Pin3 0v; Pin4 0v; Pin5 2.49v; Pin6 2.5v; Pin7 2.53v
Now (Very Dim Picture) Pin1 1.94v; Pin2 1.94v; Pin3 0v; Pin4 0v; Pin5 2.49v; Pin6 2.5v; Pin7 2.27v
Given that my screen and inverter are OK how can I get my bright picture back, using the keyboard dim keys only make it darker. There is no graphics card it must be built in and I get a perfect picture on an external monitor. Have I upset a setting on the motherboard by trapping the Pin1 wire and if so how can I reset it? Could I shock it back again? If so what pins and voltage would you suggest and how now that the voltage in Pin1 is so low it does nothing when I touch it to Pin4?
October 31st, 2008 at 2:25 pm
I’m having backlight issues with a 17″ PowerBook G4. The light went out right after I replaced a bad video cable. OH, cruel irony!
July 7th, 2008 at 8:01 pm
Christian,
I think you have a problem with the LCD screen. I published your question and some suggestions here: Laptop LCD lights up but there is no image
July 7th, 2008 at 3:37 pm
I have an interesting problem.
The backlight on my laptop LCD lights up..but there is no image
Even when its Posting (before booting in the OS)
there is no image.
HOWEVER if i put pressure on a corner of the lcd, the image shows up.
Is it a bad Inverter or video cable or other?
June 17th, 2008 at 9:22 pm
Thank you Derek,
That’s a good point and the only reliable method to find out what is causing the problem, the backlight lamp or the inverter.
June 17th, 2008 at 8:32 pm
if you want a test backlight bulb, you can just get those CCFL light kit for case modding on ebay. they are cheap, like 5 dollars i think. you might need to reharness your connections to make them compatible however.
May 1st, 2008 at 11:56 am
Mark,
If the screen lights up, this is not an inverter problem. This first think to check would be the video cable. Try reseating the video cable on the back of the LCD screen. It’s possible the cable got loose. If reseating the video cable doesn’t help, I would probably try replacing the cable.
Could this be a motherboard problem? Yes, but I would play with the video cable first.
By the way, this could be a LCD problem too.
April 26th, 2008 at 2:54 pm
I have a Toshiba a45-s150 with LCD problem. The lcd lights up bright but have no images. An external monitor works fine when hooked up. Could this be an inverter problem or a motherboard problem. The video card is intergrated.
Thanks
Mark
April 20th, 2008 at 10:23 am
Morris Rosenthal is the man! Thanks for that post.
Whipped out my Multimeter and checked a good laptop and I see the high frequency. Then went to my dark laptop (which I can see if I shine a flashlight on it) and No Frequency. My screen lights dimmly when cold booted and in a short time fades out.
I had previously inspected and flexed the inverter input cable while running didn’t change anything. I also replaced the inverter with one from ebay but it didn’t help (in fact it was worse). I suspect it was a bad part so re-installed the original.
After using your simple test, I think I’ll try to pick up another inverter.
April 8th, 2008 at 6:20 am
Hi, I have a problem with my laptop display truning dim after I start the computer. I replaced already the lcd inverter cable and is still gives me the same problem. I tried to test the inverter input with a voltimeter and getting around 14 Voltage3 which it should be alright, then I tested the inverter output with one of those light bulbs used for light up the mod cases and it will light up but intermittenly. Is that how it should be or is a case of not enough power? Does that mean that the inverter is faulty? Any help would be greatly appreciated..
March 3rd, 2008 at 9:10 am
I have Toshiba 2435 -S255 Laptop, from two weeks i have send it to a non certified service center to check the sound line-out problem, but they didn’t know how to fix it, anyway after two days from the service, when i started my laptop the backlight of LCD worked for like two seconds then turned off, i went back to them and they said to me it is FL – Inverter problem, so they replaced it, which fixes the problem, but after that i have this wired problem when i shutdown the laptop by removing AC adapter & Remove the battery (the non traditional way), the backlight stopped working, but when i shake the laptop a little & start the laptop the light works back again, So anyone have any idea why when i shake it, the light works? this is really confused me!!!!!!???? Adam
January 14th, 2008 at 8:17 am
I’ve been fooling around trying to work out an decent, non-invasive laptop inverter test that doesn’t require a spectrum analyser for years. Finally stumbled on the idea of using a decent multimeter with a KHz reading or a true RMS meter, and just using the probes as an antenna. Did an illustrated page on both:
http://www.fonerbooks.com/test.htm
The cheaper meter doesn’t work on higher frequency inverters.
Morris
December 26th, 2007 at 6:33 pm
Hi,
I have a compaq presario V2000 with monitor issues. I just replaced the inverter a about 2 weeks ago, and everything was running smoothly and then all the sudden, back to the very dim screen. Still sounds like an inverter issue. But I don’t think I bought a faulty inverter, as it did work for about 2 weeks. So is it possible there’s a short in the computer that is blowing the inverters? Any way I can find where that is without sending the whole thing into a shop and paying stupid amounts of money? I’m thinking maybe its possible the inverter just wasn’t connected all that securely and somehow came lose… But I didn’t drop the computer or anything, so I’m not sure how that could have happened… Any ideas you have would be greatly appreciated!
Thanks!
October 31st, 2007 at 4:21 pm
Sorry i forgot to mention that the laptop startup to the windows all the time!!
October 31st, 2007 at 4:19 pm
Hello
I’ve got a toshiba inspiron 8600 and it worked fine for three years and now the screen just went black no light or image at all,i tried contrast settings, i pointed a light against the screen, if i plug the screen into a crt it works but the tft is dead, i tried to read any voltage on the output of the inverter with a multimeter,and it was always 0,what it could be,i tried to read it in some resistance and i only got values bigger than 0 in 2resistence,have i got a bad inverter are this values because i’m using a multimeter, should i try a new screen could it be the black light,how do i test it???
October 13th, 2007 at 12:09 pm
This is a great site, and from what I’ve read, I’m guessing I also need to replace my inverter. I can see the image on my screen with a flashlight, but no backlight at all. I get no power reading at all on the output of the inverter with my meter. Image shows fine on an external monitor. It is a Toshiba Satellite A35-S159 laptop, but while looking for the inverter online, I notice several different ones listed for the A35 Series. Are there actually different inverters that work with my laptop? What would happen if I bought and connected the wrong one?
September 20th, 2007 at 7:20 am
I assume other Toshibas with inverters may be similar however here are the voltages for a working Toshiba TE2100 Inverter by wire color with ground taken from the LCD Frame:
Blue: 4.58
Green: 4.58
Yellow: .1 (Brightness 1) to 3.2 (Brightness
Orange: .04 (GND?)
Red: .04 (GND?)
Brown 4.9 (5v Pwr ?)
Black 4.9 (5v Pwr ?)
At the mainboard end of the cable, these seven wires can be located on the left end of CN1 just under the left side of the keyboard cover as follows.
Green, Orange, empty, Black
Blue, Yellow, Red, Brown
The above voltages all fall to 0 when the lcd screen is turned off.
Input voltages can be measured with a pin tightly taped to the end of your vom. Fasten ground to your lcd screen mounting frame.
The inverter output can be measured for one glimpse of time with a 600 vac or higher multimeter.
(DANGER, TAKE HIGH VOLTAGE MEASUREMENT CAREFULLY AND AT YOUR OWN RISKS)
To measure the output, put the computer in hybernation state or power off, unscrew the inverter, flip it over to the component side and then gently pry away the plastic cover away from the input side (7 pin) of the inverter where it is glued. This will free the plastic cover to slide away somewhat from the inverter’s output high voltage side. Now startup the computer and first test to make sure an external monitor works. After determining that the computer’s screen should now be on, set your meter to 600vac or higher and locate the solder joints to the inverter’s output connector on the component side (back). Now watch your meter as you connect to the solder joints. You will see the meter quickly register some high voltage before automatically shutting down the inverter. You may have to hybernate or power down your computer down a couple of time to re-power your inverter and verify the inverter’s ac. The inverter shuts down quickly just after you touch the meter’s leads to the output.
July 31st, 2007 at 7:23 pm
Neil or Laptop Freak,
Do u have disassembly instructions for this laptop. I have a Gateway M305crv laptop. However, mine never gets a chance to boot-up. Everytime it trys to boot the OS I hear this clicking (one click) sound and then it turns off and restarts again automatically. I hear the fan going, so I don’t think it’s a heating problem.