iMac 21.5-Inch "Core i5" 2.3 (Mid-2017) 820-01069-b

[alfredodinolfo]

Green light only Led #1, #2,#3.
led #4 is off;
fan run on;
no image on external monitor;
no reset PRAM and no mouse activity.

I tried to change bios and I verified activity on bios chip.
No diagram or boardview for this board.
Anyone have fixed?


- - - - Board UMA - - - -

[mon2]

Re: iMac 21.5-Inch "Core i5" 2.3 (Mid-2017) 820-01069-b

What is the history of the computer ?

Was it working before someone opened the unit for some upgrade ?

LED # 4 is a failure to communicate with the LCD display. Check the LVDS cable to the display. Is the blade connector still properly soldered on the logic board ? Trace where the LVDS cable is connected to the LCD and confirm again for a proper connection.

However if the external monitor is also not working then this is graphics card related.

Trace the voltage from the power supply to the LCD display. Are these cable harness connections ok? On past other imac models, DIY customers damaged this area and we had to dissect the cable harness (both the LVDS ipex blade connector) and the power cables and re-attach them.

To confirm, you are not getting the power up chime ? PRAM reset is NOT working for you?

I would check the voltages on each coil to see if anything is not in a 'normal' voltage range.

[hvencl]

Re: iMac 21.5-Inch "Core i5" 2.3 (Mid-2017) 820-01069-b

Hi all. In my case with this exact model I get first and third led lights coming up and cycling again only first and third. Second one never comes up and fourth if off because the screen is of. I am thinking it could be bad PSU. Appreciate any suggestions.

[mon2]

Re: iMac 21.5-Inch "Core i5" 2.3 (Mid-2017) 820-01069-b

@hvencl, try reseating the ram.

[hvencl]

Re: iMac 21.5-Inch "Core i5" 2.3 (Mid-2017) 820-01069-b

@hvencl, try reseating the ram.

Thanks, I tried and got it once to power up with only one Ram stick in. When I got all connected again with one stick in the problem returned. In the meantime I ordered a replacement PSU so I will try again when it arrives.

[mon2]

Re: iMac 21.5-Inch "Core i5" 2.3 (Mid-2017) 820-01069-b

Remove the RAM stick. Power up without the ram stick. What are the results?

If you have another free RAM stick socket, seat your ram inside it and test again.

Perhaps your RAM is defective.

[hvencl]

Re: iMac 21.5-Inch "Core i5" 2.3 (Mid-2017) 820-01069-b

Update: dismantled everything again, cleaned RAM stick contacts with alcohol, checked the voltage on PRAM battery 2.8 Volts so changed it just to be sure. After that it started without RAM sticks. So I asembled everything with current/old RAM and it works. Restarted it a few times and made a power cycle and so far everything works. I still haven't tried unplugging it (the problem occurred last time I unplugged the computer because I wanted to put it in another room). Could it be that the battery made all these problems

[mon2]

Re: iMac 21.5-Inch "Core i5" 2.3 (Mid-2017) 820-01069-b

Good job! I think the cmos battery (coincell) could have been the fault.

See here:

https://discussions.apple.com/thread/7961982

[hvencl]

Re: iMac 21.5-Inch "Core i5" 2.3 (Mid-2017) 820-01069-b

Update: dismantled everything again, cleaned RAM stick contacts with alcohol, checked the voltage on PRAM battery 2.8 Volts so changed it just to be sure. After that it started without RAM sticks. So I asembled everything with current/old RAM and it works. Restarted it a few times and made a power cycle and so far everything works. I still haven't tried unplugging it (the problem occurred last time I unplugged the computer because I wanted to put it in another room). Could it be that the battery made all these problems

So I have to report back again that the computer is not working any more. Now it has only led 1 and 2 on. Led 3 flashes and turns off. No chime, screen is black and fan is on. I guess the GPU died and it is integrated on this model. Tried reflowing the CPU/GPU chip with hot air station but there is no change. Just Led 1 and 2 are on.

[letsrock88]

Re: iMac 21.5-Inch "Core i5" 2.3 (Mid-2017) 820-01069-b

Hi all I have same problem here. In my case with this exact model I get first and third led lights coming up and cycling again only first and third. Second one never comes up and fourth if off because the screen is of. I am thinking it could be bad PSU. Appreciate any suggestions.

So i need board view and schematic diagram for Board No.820-01069-B

[Aliencomputres]

Re: iMac 21.5-Inch "Core i5" 2.3 (Mid-2017) 820-01069-b

Helo,
What is the history ?

[sierra1212]

Re: iMac 21.5-Inch "Core i5" 2.3 (Mid-2017) 820-01069-b

Hello ,
I have the same board, but different state
Green light only Led #1,#3.
led #2 ,#4 is off;
fan run off;


Anyone have fixed?

[reformatt]

Re: iMac 21.5-Inch "Core i5" 2.3 (Mid-2017) 820-01069-b

Most iMac board failures for me are shorted caps, usually towards the bottom of the board where it sits below the screen. Sometimes the short is on a switched power rail.

No schematic available for this version of board, closest to it is 820-00034. My strategy would be just to put my meter across caps at the bottom area checking for one that is shorted. Thermal camera helps too if you do find a short on a rail somewhere.

[aksel3]

Re: iMac 21.5-Inch "Core i5" 2.3 (Mid-2017) 820-01069-b

Hello ,
I have the same board, but different state
Green light only Led #1,#3.
led #2 ,#4 is off;
fan run off;


Anyone have fixed?

Power chip issue. change isl62383c if only led 1 and led 3 on led 2 off led 4 off

[aksel3]

Power chip issue. change isl62383c and 7568 transistor. if only led 1 and led 3 on led 2 off led 4 off