A1502 820-4924 vs 820-3476 LCD Pinout

[aazjo]

After searching around and not finding a satisfactory answer, I've decided to ask here. I have a 2013/2014 A1502 entire laptop with a 820-3476 board and a separate 820-4924 board only. I want to put the 4924 into the existing chassis.

After comparing the boards I obviously see that the trackpad, trackpad cable, and cable clamp/cover are different which isn't too big of a deal as the parts are fairly cheap.

However, LCDs are in short supply and expensive so I was checking out the LCD/LVSC pinouts and see that pin 5 and pin 10 are swapped (LCD_IRQ_L and EDP_PANEL_PWR_OR_PSR_EN/PP3V3_S0_EDP_R). It looks like LCD_IRQ_L is just moved, but the 4924 introduces the U8310 in between PP3V3_S0 and the LCD. I read somewhere else that they may have moved the voltage monitoring circuit from inside the LCD to outside, but I don't know how true that it.

After studying the schematics for both boards, it looks like I could just swap the pin 5 and pin 10 and it should work. Not sure what would be easier though, to swap it on the motherboard, the cable, or the LCD board. Looking for some advice from anyone who may have done this.

Thanks in advance.

[piernov]

Re: A1502 820-4924 vs 820-3476 LCD Pinout

2013 and 2015 LCD assembly aren't compatible. Backlight won't work properly.
They're worth gold so last thing I'd try is mess with it and inadvertently kill it…

[aazjo]

Re: A1502 820-4924 vs 820-3476 LCD Pinout

Thanks Piernov. I was trying to analyze it from an electrical perspective to understand the differences. I agree they are expensive (worth their weight in gold).

[aazjo]

Re: A1502 820-4924 vs 820-3476 LCD Pinout

I've been all over the backlight circuits of both schematics and they look identical except a few extra decoupling caps on the PPVOUT_S0_LCDBKLT output. Those decoupling caps wouldn't do much except reduce the noise on the line and provide smoother power.

Also have been looking over the LCD circuits more and at most I see a few more decoupling caps, the U8310 (which looks like a protection circuit that does nothing more than what EDP_PANEL_PWR_OR_PSR_EN did going directly to the panel), and some FLs (FL8300-03) on the data lines. Other than that they changed a few net names and swapped pins 5 and 10.

Can you show me any electronic proof that it won't work besides pin 5 and pin 10 being swapped? Is is possible that there is a software/protocol/driver difference that would cause it to not work?

I know that I'm pushing it, but I'm tempted to buy a slightly broken screen to try it on.

[aazjo]

Re: A1502 820-4924 vs 820-3476 LCD Pinout

Just learned about EDID information stored in the LCD's eeprom. Do you think it would be possible to copy a 2015 MBP LCD EDID and put it on a 2014 MBP LCD. I've recently been getting into eeprom reading/writing. Seems like it would be easy to reprogram a little I2C 24C chip.