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CCFL inverter pinout help (n0ob)

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garrettp

New Member
Hi all,

I am new to the forums but trying to figure something out with LCD's from apple.

I have a 20" iMac G4 with an LCD that does not light up. I have tried 3 different inverters to no luck. At night it does glow enough to use it in extreme darkness but that is about it. So, the CCFL's are getting some power but I need to figure out if the CCFL's are bad or if it a problem from the logic board (Apple's term for motherboard).

The inverter has 8 pins in as described below. I can supply pictures of PCB if needed.

Blue = 11.93v
Red = 11.93v
Blk = GND
Blu = GND
N/C
Yel = .2mv
Prpl = 3.262v
Orng= no voltage detected

So, it seems to me that with the 12V (blue and red go to fuse on inverter PCB) and 3.3v, the lamps should ignite correct?

However, I am under the assumption that the 3.3v is the on and off and the Yel & Orng are for brightness control. Does that sound correct?

With that, I have a 20" LCD with known working CCFL's coming from an iMac G5. The only problem is it uses LVDS vs TMDS that the G4's use. I do not know if it will simply plug into the G4 even though it is the same connector. I do think however that I can plug the G4 inverter into the G5 display and get lamps (from what research I have done). I would however like to be able to use [on of] the displays as an external monitor and do have pin configs for the video cable. I just need some help with getting the inverter powered up.

Thank you for your help and man am I glad I found these forums. I am not an electronics guru but I am great at SMD rework and have a little knowledge of how things work.

garrettp
 
Inverters need to be told to light up, they are told how bright to light, and they also send a signal back confirming correct operation - so in your case it may be that it's not receiving the ON signal, the brightness signal, or there's a fault and it's telling the processor to shut it down.

Even a single faulty CCFL tube could cause it.
 
I've replaced the CCFL in a laptop. Not fun, but doable. There's some myth going around that the problem's always the inverter (probably because it's easier to replace). Guy at work went through this. I told him it was probably the CCFL. Got a new one off Digikey (wasn't expensive) and lit it up on the table to confirm before opening the notebook and replacing the tube. I suggest this approach.

There's little transparent rubber o-rings on the old tube. Save them for the new tube.
 
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I have the LCD assy completely apart and it is rather simple (other then trying to keep it clean). ;)

As for signal to the inverter, I need more info not just someone telling me what I stated above ;) :p

here is a pic of the exact inverter:

**broken link removed**
 
Ccfl

HI there,
well i hate to say it but i think you're on the wrong track here, I have spent a couple of years buying/repairing and reselling laptops and 99% of the time, if the screen is dark but still has a faint image, then its not the CCFL but the inverter board that's bad. basically, the bulb works or doesn't work, no in betweens, so any visible image tells me its the inverter.
just search the inverter board number in ebay and i'm sure you'll replace it for under $20
 
oh and you can't mix and match inverters,

There are only two connction tyeps for most windows Inverter boards , not sure about Mac's, but there are literally tghousands of different inverter board models and i have hardly ever been able to simply mix and match because of the connectors, . they are all configure indiviually for the screens setups i believe.
 
I have tried 3 different inverter boards. 2 from the same place and the second they said they tested. I then purchased another on ebay that was confirmed working. Still no lamps.

What I need to figure out is what pin is for what. I know it is getting 2-12v signals and one 3.3v, which I believe is all that it needs. However, I am wondering if it has something to do with the brightness control. I do not believe there is a signal sent back to the logic board. I do know there is a voltage send to the inverter though for brightness and it seems that may be the culprit. I thought about installing a potentiometer from the 3.3v to the yellow and then the orange to see if that gets me anywhere but I am afraid of damage to the inverter (no biggie, I have 2) or worse logic board.

From what I found on the internet, there should be voltage for the one off (0v=off) and 0-4.8v for the dimmer.

I have an LCD from a G5 coming from ebay but the G5 uses LVDS vs TMDS from the G4 logic GPU. I do not know if that is compatible (but I will find out ;) )

So, the search continues for the pin that controls brightness and tells the thing to turn on. I do not have a VOM capable of checking the inveter output voltage :(

Thanks for the help and suggestions so far. What a great forum :D
g
 
I got another inverter and still no workie. I then tried to hook the inverter to a Power Supply from a computer (PSU). I tried several different combinations on the 3 pins that I do not know what they do. I Know that pin 7 is the 3.3v on off. The other pins I tried tying together as suggest in one inverter test I found to no luck. I then tried running the 5v from the PSU with a 1,000k pot and still no luck, even when fed what was suggest in some other docs I found.

According to what I have found, the PMW of the inverter (which controls brightness), send a signal back from the input to verify the brightness. I tried every combination under the stars and still no avail.

So, with that, I could order new CCFL's and inverters to match but I think I am just going to forgo buying any more inverters and put in LED's. I can run the LED's off of the 12v feeds (x2) and put a pot on there and mount it through the back of the display. I will have to start another thread so I can make sure I do not blow out the PSU of the mac with too many LED's though ;)
 
Might be a blown microfuse on logic board

I'm having a similar problem on an iBook G4. I found an open fuse.

Follow the inverter board wiring to the logic board and look for a surface mount nano fuse that powers the inverter board. Mine is tiny, translucent surface mount fuse near a number on the board that starts with F and it says: TH on it.

I get full 10v+ voltage on one side, zero on the other.

I do not want to replace the motherboard. And I am afraid to bridge it because I don't know what blew the fuse! I am having no luck identifying the existing fuse. I found one site in Singapore that is selling 5 amp 125v very fast acting ceramic fuses (on a page with iBook G4 parts) but cannot verify the specs needed. The voltage is "high voltage" but 5 amps is huge.
 
Inverter board problems

Hy
I saw, this is an old theme, but, maybe can help. I am in "electronics world" about 15 years, now, I'm reparing the notebooks and LCD monitors but I'm living in country where is so dificult to buy any new part (inverter, motherboard...).
When we talk about inverter for notebook, I found that inverter have just 4 pins (not know what's the case in Mac Books), with only different arrangement for different laptops, but the same driving voltages, so you can put them correct after you identify them. These are:

0V-GND
5-12V Power supply (12V for LCD monitor, 5V for laptop)
0V(on) or 5V(off) backlight
and 0 up to 3.3V analog voltage for backlight stepping (IC on inverter is converting this into PWM, to regulate backlight intensity)

Just don't connect GND to wrong pin, you can damage the inverter board or fuse(maybe).

There is no special back signal from inverter, motherboard just have "intelegent" supply for inverter.

Frequently appearing problem in damaged inverters is high voltage transformer, his output coil burned. You also can replace him, solder the another one from same diagonal LCD screen inverter (they have the same transformers, same output voltage for ccfl). Longer ccfl works on higher voltage, so if you resolder the transformer from 17" to 15.4" (for example), ccfl lamp can die on highest intensity of brightness.

I fixed several notebook damaged inverters, replacing an incompatible inverter with modified arrangement of input wires. Some input conectors have (for example) 10 pins, but 4xGND, 4x5V, on/off and dimming siganl, but it's the same, just 4 different.

If you have any question, contact me or post the problem, maybe I can help :D
Sorry for language mistakes.
Good luck!
 
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to be sure the inverter is broken...
if I disconnect all wires except 12v and ground, then shortwire ground to all those disconnected pins on inverter side, if inverter was good it should lid up... RIGHT?
and then... I should be able to measure some resistance on output from the coil, if it's burnt, there will be infinite resistance. RIGHT?

Hy
I saw, this is an old theme, but, maybe can help. I am in "electronics world" about 15 years, now, I'm reparing the notebooks and LCD monitors but I'm living in country where is so dificult to buy any new part (inverter, motherboard...).
When we talk about inverter for notebook, I found that inverter have just 4 pins (not know what's the case in Mac Books), with only different arrangement for different laptops, but the same driving voltages, so you can put them correct after you identify them. These are:

0V-GND
5-12V Power supply (12V for LCD monitor, 5V for laptop)
0V(on) or 5V(off) backlight
and 0 up to 3.3V analog voltage for backlight stepping (IC on inverter is converting this into PWM, to regulate backlight intensity)

Just don't connect GND to wrong pin, you can damage the inverter board or fuse(maybe).

There is no special back signal from inverter, motherboard just have "intelegent" supply for inverter.

Frequently appearing problem in damaged inverters is high voltage transformer, his output coil burned. You also can replace him, solder the another one from same diagonal LCD screen inverter (they have the same transformers, same output voltage for ccfl). Longer ccfl works on higher voltage, so if you resolder the transformer from 17" to 15.4" (for example), ccfl lamp can die on highest intensity of brightness.

I fixed several notebook damaged inverters, replacing an incompatible inverter with modified arrangement of input wires. Some input conectors have (for example) 10 pins, but 4xGND, 4x5V, on/off and dimming siganl, but it's the same, just 4 different.

If you have any question, contact me or post the problem, maybe I can help :D
Sorry for language mistakes.
Good luck!
 
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