replace blow inductor with jumper???

[garrettp]

I have an iMac G4 with screen issues. The CCFL's do not light up and I have replaced with several inverters with no luck. I have checked voltages and I am getting what seems to be correct from the logic board (what Apple calls a mother board). The CCFL's light only enough to be viewed in complete darkness.

While replace the hard drive today I noticed a blown inductor. I ticked it with my finger nail and it came off. Now that it is off the PCB I get NO display lighting at all.

So, with out knowing what the value of the blown inductor is (and is there anyway to figure that out), can I just replace the inductor with a jumper? The inductor has to be for the display since now I get no CCFL lighting at all. I have not checked voltages to the inverter since this happened and I guess I would worry as to why the inductor blew and if a jumper would just cause a short.

Below is a pic of where it was and then following a similar inductor.

Any help would be greatful to me.

Now that I look at this pic, I never traced the traces. The connector to the left is for the inverter cable.

**broken link removed**

The below is just a random spot on the PCB.

**broken link removed**

Again, Thank you for any help,
g

 

[dknguyen]

Replacing an inductor with a jumper (especially in a CCFL) will probably cause more things to burn out as it is likely the inductor is being used to step up the voltage and a jumper cannot slow down the rise of current enough for the power supply controller to keep it under control (ie. it would as you suspected cause a short-circuit when the switching transistor turned on).

 

[garrettp]

Thank you for the info. Now, I took the second picture to find out if I can just replace the inductor willy-nilly (no offense to Willy Nelson or any named Nilly ). If I take a similar inductor from a different circuit board can I put it on there?

Chances are I will not be using the OEM inverter on the iMac anyway. I have an after market inverter coming today sometime. But, It would be nice to know what is causing the issue in the first place. And even though I am replacing the inverter with after market it would be nice to use the software based brightness control. Otherwise I will just put a small pot protruding out of the back of the LCD assy.

I assume by the pics that there are no value marking on these itty bitty inductors. Not like it would matter though since the bad one is mostly melted .

Thanks,
g

 

[mvs sarma]

Thank you for the info. Now, I took the second picture to find out if I can just replace the inductor willy-nilly (no offense to Willy Nelson or any named Nilly ). If I take a similar inductor from a different circuit board can I put it on there?

Chances are I will not be using the OEM inverter on the iMac anyway. I have an after market inverter coming today sometime. But, It would be nice to know what is causing the issue in the first place. And even though I am replacing the inverter with after market it would be nice to use the software based brightness control. Otherwise I will just put a small pot protruding out of the back of the LCD assy.

I assume by the pics that there are no value marking on these itty bitty inductors. Not like it would matter though since the bad one is mostly melted .

Thanks,
g

Correct.
lot of scrapping to see whether the board can be cleared without damage to other through hole wires(if they have not formed Low insulation by now). seeing the extent of damage, doubtful whether one could restore it with any certainty of performance. a thorough check is needed to sort out reason for this level of burning and whether no there component is shot ans restoration trial by a shorting wire would not repeat the earlier situation of fire.