RepRap full graphic with MKS Gen L

Hi first time poster here,
I have a Anet A2 plus that I successfully upgraded to Marlin so I could enable thermal protection and mesh bed leveling.
While upgrading the hotend I managed to damage the main board, so was forced to replace.
I purchased a MSK Gen L, and suitable stepper drivers. I hadn't realised that the Gen L doesn't have an SD slot, so had to purchase a RepRap full graphic smart controller as well.
After some initial problems I managed to flash the Gen L, I think, but I cannot get the display to work.
The backlight lights up, but the display is blank.
I'm sure I have enabled the display in marlin, I've even tried to use my old Anet display, obviously setting correctly in marlin, but neither display works?
Any help would be really appreciated as I'm running out of ideas and really want to get printing again!

Thanks
RH

Some manufacturers like to put the LCD connectors on backwards! Same pinout just rotated 180 degrees. Which you can't try do due to the plastic key.

Work out where the Gnd and +5v is on your is on your display connectors (its at one end or the other of EXP1. GND is normally connected to the sdcard shield) and compare it to the
MKS Gen L pins diagram [github.com]

Edited 1 time(s). Last edit at 06/18/2020 05:16PM by Dust.

I've already rotated the cables.
If i connect correctly the display beeps, I've been told this indicates it's connected wrong.
If I rotate the connectors the beep stops and the backlight comes on.
If I press the knob the main board lights a blue led

Thanks

Have you adjusted to contrast? small variable resistor on the back. Sometimes blue thing on front..

Edited 1 time(s). Last edit at 06/18/2020 07:11PM by Dust.

Yep, tried that as well!
Should the old Anet display work?

Can we use some actual science here vs pseudoscience?

unplug the lcd, get a multi meter and set it for continuity.

Measure from the metal shield over the sd connector to the corner pins of exp1 connector. work out which one is ground.

Make sure this gnd is connected to the gnd pin on the controller exp1 socket as pictured in the MKS Gen L pins document.

upload your Configuration.h (or pastebin it and share the link)
make sure REPRAP_DISCOUNT_FULL_GRAPHIC_SMART_CONTROLLER is the only lcd enabled.

take a picture of the REPRAP_DISCOUNT_FULL_GRAPHIC_SMART_CONTROLLER and share it, to make sure it is actually a REPRAP_DISCOUNT_FULL_GRAPHIC_SMART_CONTROLLER
and not a REPRAP_DISCOUNT_SMART_CONTROLLER or something else entirely.

Thanks for all the advice, the display board was defective, replaced and all working well now, except for a cooling issue that I will place on another thread.