Imac no image

[LaptopRepair]

Hello;

My next job after more than a month.

I got an Imac A1418 from another shop. When plugging to power it gives the chime but no picture on the screen. After 50 seconds the fun begins to spin.

The other shop has already bought a new screen.

I ve changed the LVDS connector on the motherboard, because it was shorted. Also changed for him a new LVDS flex cable, but still no screen.

Please any steps to follow?

Greeting

 

[dukefawks]

The fan spinning up is either a missing temp sensor which is a separate sensor plugged in to the LCD board. What was shorted in the LCD connector? Get a known good test screen, cracked one for testing.

 

[LaptopRepair]

Pin 1 and 2 of the lcd connector were burned because of the short also the cable connecting the board to the lcd panel. Like i ve said i resolderd a new connector and changed the cable with a new one.
the screen i m using is a new one.
i m testing it without plugging a hdd.
what kind of temp sensor should be connected to the LCD board? Please any picture of this can help.

 

[dukefawks]

I don't know the board number but I assume the coil that is in the power to the LCD has burned when the connector shorted. This is L9100 in the 820-3302 diagram.

Next to the connector on the LCD is a small 2 pin connector, that is where the LCD thermal sensor needs to go. It is probably still stuck on the old LCD.

 

[LaptopRepair]

No Title

Yes, indeed i ve found a connector on the LCD PCB that has no cable connected to it. I am not sure if this what you mean with temperature sensing. Here bellow a photo of it. I could found a substitute cable that fit this connector, but where I couldn't find on the board where it should plugged. Or must be connected to another place?

the coil in the power rail on the logic board going to the LCD connector was also changed already. Forgot to tell you. It was missing.

 

[dukefawks]

Get the old LCD back, it is still on there. Also good for testing purposes, because you do not know if this LCD is working.

Check if 12V is coming to the LCD connector through L9100.

http://www.ebay.com/itm/New-LCD-Skin...-/182363285425

 

[LaptopRepair]

I ve placed the old LCD, but no sceen is coming.

Is it mandatory to use that LCD sensor to get image on the sceen?

I ve connected the imac to an external screen but also no beeld is showing up.

Can you tell me what are the important signals that need to be on the LCD connector to get image?

Greeting

 

[dukefawks]

Inspect connector and cable. Sensor is not needed to get image. Check 12V on L9100 too.

 

[LaptopRepair]

12V21 is present on the L9100. The continuity of the 12V through the lcd connector is OK.

Is there a way to test if the LCD is OK?

 

[dukefawks]

Yes, try a known good LCD. Some of these Chinese replacement ones have a EDID ROM that is empty, so no image.

 

[LaptopRepair]

I ve bought a dvi/hdmi cable conerter. Plugged it the board and connected it with a TV. I got the next picture. Check the small video.

 

[dukefawks]

Seems like a fucked GPU to me. Heat it up and try again. Probably the N13E GPU, good luck finding those in real new ones......