Originally known as "The New iMac" the iMac G4 was created to replace the iMac G3 as Apple's all-in-one desktop computer. The G4 is easily recognizable by its swiveling monitor mounted above the hemispherical computer. Steve Jobs quoted it as being "a design that will last till the next decade."

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Blank Screen, but external works fine

iMac G4 20 inch model has a blank screen. But working fine when connect to the external monitor over miniVGA.

Screen backlight is okay, brightness is changing, but no any sign of picture.

I did a monitor swap from the same model with the same model number, but it is still blank.

Looks like video chip is okay and provide signal to the external monitor but no signal to the TDMS on internal screen.

Please help me.

Thank you

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I did a swap from the display assembly.

Where is fuse located in the logic board ?

is this fuse for internal monitor only ? because external working fine

I did visual check of TDMS pins

on the board- looks okay.


If you still have the other system handy try plugging it in directly on the logic board (just be careful as the cord is very short and easy to damage). If not, I would first swap out the cable (more likely worn out).


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How did you swap out the display? Did you do it from the logic board or from within the display assembly?

Sounds like either the TDMS Cable is bad or you have a damaged logic board (fuse blown/pins damaged on TDMS connector)

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