Controller LCD contrast issue I am working on a new Prusa/Graber i3 printer, but am having an issue with the LCD. Here's what I am using: Arduino Mega 2560 Ramps 1.4 RepRapDiscount Full Graphics Smart Controller (previous edition w/ potentiometer and red PCB) Marlin Firmware - Stable branch (downloaded this weekend) I have been successful in building the Marlin firmware and downloading it to the Arduino. The controller boots up and the startup screen and then info screen display as expected, but I am having an issue with the contrast. The screen is almost entirely white, making it difficult to read. Looking at the display from an angle makes it readable, but obviously, I'd like to resolve the problem. Changing the setting in the firmware's menu makes no difference. I've also changed the default value in the code and recompiled and downloaded it. The new default value shows up in the config menu, but the contrast is apparently the same. I have also changed the potentiometer to see if that would effect the contrast, but the pot seems to make no difference at all. In fact, I even removed the pot from the board (desoldered it) and again, the contrast was identical. Anyone have a suggestion as to what is going on? I suspect one of the following: * The Marlin firmware doesn't support the older version of the RepRapDiscount display board. * The Display board is not functioning as expected * There is something in the firmware code that I need to change to support the older board. Any and all suggestions are welcome and appreciated! -David. https://reprap.org/forum/read.php?13,448609,448609#msg-448609 Mon, 08 Jun 2026 10:18:35 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?13,448609,890289#msg-890289 Re: Controller LCD contrast issue https://reprap.org/forum/read.php?13,448609,890289#msg-890289
You have no back light

The white thing on the left is part of a light that should be on while the LCD has power.

This is part of the LCD module

[attachment 119674 jhd12864-e-1--500x500.png]

Pins 19 and 20 provide voltage to the backlight, check for 5v between these two pins.]]> Dust Controllers Wed, 17 Aug 2022 11:00:45 -0400 https://reprap.org/forum/read.php?13,448609,890288#msg-890288 Re: Controller LCD contrast issue https://reprap.org/forum/read.php?13,448609,890288#msg-890288 Me esta dando muchos dolores de cabeza
Desde ya muchas gracias!]]> Leandrorioiv Controllers Wed, 17 Aug 2022 09:44:24 -0400 https://reprap.org/forum/read.php?13,448609,774215#msg-774215 Re: Controller LCD contrast issue https://reprap.org/forum/read.php?13,448609,774215#msg-774215 Here my experience with Full Graphic Smart Controller contrast issue. Same issue as many of us, so I investigate and discovered a mistake of PCB traces.
My mod needs a cutting of two traces and a soldering of two pieces of wire. In this way the original contrast pot became again operating.
Look at the attached picture.
1) Cut the traces (in Yellow)
2) Solder one wire from +5V to the pot (RED)
3) Solder one wire from pot wiper to the LCD contrast input (WHITE)
3) Switch all on and recalibrate the contrast with the pot.
Enjoy
Bye
Carlo]]> carlonb Controllers Wed, 21 Jun 2017 09:18:59 -0400 https://reprap.org/forum/read.php?13,448609,767220#msg-767220 Re: Controller LCD contrast issue https://reprap.org/forum/read.php?13,448609,767220#msg-767220 Jb Sebastian Controllers Wed, 10 May 2017 21:37:24 -0400 https://reprap.org/forum/read.php?13,448609,763831#msg-763831 Re: Controller LCD contrast issue https://reprap.org/forum/read.php?13,448609,763831#msg-763831
Which controller?
Which firmware on it?
What LCD display?
Have you checked the voltage on the 5V rail? Any change when switching from USB to power supply?
Which speed and accelleration settings for motors? Have you tried lowering speed and/or acceleration values?]]> enif Controllers Sun, 23 Apr 2017 02:49:09 -0400 https://reprap.org/forum/read.php?13,448609,763817#msg-763817 Re: Controller LCD contrast issue https://reprap.org/forum/read.php?13,448609,763817#msg-763817 Iam doing 3d printer as my project I did all mechanical work(frame x y and z axis)
But when I checked that axis after connecting with ramps it has some issues
1st issue is when I plug in usb with out connecting power supply lcd display works fine but
When I connect power supply a white screen cover the display screen .
2nd issue is I bought some motors from eBay and some from other site .The motors which I bought from eBay rotates during no load condition but when I connect threaded rod not even z axis rotates .and the motor which I bought from other site is not at all rotating its just vibrating will the problem I tried adjusting potentiometer still same vibration can anyone help me to sort this problem please]]> mohammedrizwan44@gmail.com Controllers Sat, 22 Apr 2017 21:32:07 -0400 https://reprap.org/forum/read.php?13,448609,750031#msg-750031 Re: Controller LCD contrast issue/ flashing and bleeping https://reprap.org/forum/read.php?13,448609,750031#msg-750031
I have also bought this RepRapDiscount full graphic smart controller today after I had to upgrade my Anet A8 V1.0 card to a MKS gen V1.4 as I managed to brick the Anet trying to upgrade 8-)

So the MKS gen V1.4 works apart from the old LCD wouldn't. Hence buying the 12864 LCD & despite hunting the forums on and off all day, loading and reloading different files, still it still would only flash and bleep.

That is until I came here and noticed quite by chance two different pictures of the two 10 pin EXP1 & EXP 2. " drhender " Pic has both open at the bottom,while further down, " enif "pic shows both at the top.

Mine were both at the bottom and a quick snip on both pcb connectors, EXP1 & EXP2 on my RepRap 12864 LCD to open them up to allow the plugs to 180 degree into them solved my problem.

It now works fine and I hope some one else manages to find this solution too (tu)

Good Luck & Happy Printing]]> Anonymous User Controllers Sun, 19 Feb 2017 17:31:19 -0500 https://reprap.org/forum/read.php?13,448609,734775#msg-734775 Re: Controller LCD contrast issue https://reprap.org/forum/read.php?13,448609,734775#msg-734775
So I bent the display module forwards to gain access to the pot on the display module itself and adjusted it with tweezers. Now it works fine.

Mine is a bigtreetech one.

Thanks for making us aware of this hidden adjustment.]]> DjDemonD Controllers Sun, 01 Jan 2017 18:51:06 -0500 https://reprap.org/forum/read.php?13,448609,728765#msg-728765 Re: Controller LCD contrast issue https://reprap.org/forum/read.php?13,448609,728765#msg-728765
Quote
enif
I had a similar issue with my full graphic LCD controller, but I could not even see anything from any angle. I resolved the problem by adding a 270R resistor from the contrast signal (trimpot) to the 5V line. I connected the resistor between second and third of the empty pin holes as shown on the photo.
See and THIS is why I love internet.

Thanks, man! You've just saved me a month of waiting for a replacement LCD :)]]> rklauco Controllers Wed, 07 Dec 2016 09:35:56 -0500 https://reprap.org/forum/read.php?13,448609,718593#msg-718593 Re: Controller LCD contrast issue https://reprap.org/forum/read.php?13,448609,718593#msg-718593
I have some other problem. Maybe it is connected with contrast (and maybe not)
The issue is: the picture on the screen (Graphic controller 12864) is negative.
All parts that should be white are black and vice versa.
Trimpot adjusts the contrast but picture is quite pale (withered).
Anybody had such a problem?

Thank you/]]> igorborcher Controllers Mon, 31 Oct 2016 08:42:44 -0400 https://reprap.org/forum/read.php?13,448609,716166#msg-716166 Re: Controller LCD contrast issue https://reprap.org/forum/read.php?13,448609,716166#msg-716166 [attachment 85184 20161021_204642.jpg]]]> tritodd Controllers Fri, 21 Oct 2016 21:04:51 -0400 https://reprap.org/forum/read.php?13,448609,703745#msg-703745 Re: Controller LCD contrast issue https://reprap.org/forum/read.php?13,448609,703745#msg-703745
Just a note for those who happen to find this very useful post: it helped me rescue a defective LCD screen too.
A 560 ohm resistor between pins 2 and 3, as explained in the other posts, and the contrast is back.

Many thanks to those who found this trick ;)]]> Enrico Controllers Mon, 29 Aug 2016 07:29:01 -0400 https://reprap.org/forum/read.php?13,448609,673307#msg-673307 Re: Controller LCD contrast issue https://reprap.org/forum/read.php?13,448609,673307#msg-673307
I buy the same kit : ramps 1.4 + RepRapdiscount full graphic display, and after televersing marlin, the screen lights up but nothing appear on it.
It try a 220 and 440 between pin 2 and 3, but nothing change.

What Am I doing wrong ?

Thanks]]> davidmarli Controllers Sat, 11 Jun 2016 03:18:26 -0400 https://reprap.org/forum/read.php?13,448609,659057#msg-659057 Re: Controller LCD contrast issue https://reprap.org/forum/read.php?13,448609,659057#msg-659057
[attachment 77379 P_20160501_181537.jpg]

[attachment 77380 P_20160501_181626.jpg]]]> webliya Controllers Sun, 01 May 2016 11:22:12 -0400 https://reprap.org/forum/read.php?13,448609,630474#msg-630474 Re: Controller LCD contrast issue https://reprap.org/forum/read.php?13,448609,630474#msg-630474 Khalid Controllers Tue, 23 Feb 2016 03:33:21 -0500 https://reprap.org/forum/read.php?13,448609,623993#msg-623993 Re: Controller LCD contrast issue https://reprap.org/forum/read.php?13,448609,623993#msg-623993
[www.youtube.com]]]> Artemmih Controllers Tue, 09 Feb 2016 14:46:06 -0500 https://reprap.org/forum/read.php?13,448609,618789#msg-618789 Re: Controller LCD contrast issue https://reprap.org/forum/read.php?13,448609,618789#msg-618789 shirty Controllers Sun, 31 Jan 2016 12:05:42 -0500 https://reprap.org/forum/read.php?13,448609,607435#msg-607435 Re: Controller LCD contrast issue https://reprap.org/forum/read.php?13,448609,607435#msg-607435
I have the same banggood display. Was your display totally white before your fix?
I have

A cross post to my detailed description of my issue.

[community.robo3d.com]

I'm still stuck. I'm not sure if my controller is bad or not.

Thanks
]]> murraypetera Controllers Sat, 09 Jan 2016 20:01:30 -0500 https://reprap.org/forum/read.php?13,448609,601834#msg-601834 Re: Controller LCD contrast issue https://reprap.org/forum/read.php?13,448609,601834#msg-601834 I had idea to drill hole id plate above but after unsoldering I measured, and calculated that it would be directly on the path on second side of plate. Uffff, it was real hazard ;-), So - DO NOT DRILL HOLE!!!
[attachment 68440 IMG_20151228_215141.jpg]
On the picture you can see pot, gold pins and gold pin connector. Remember that plate is both side so be careful with unsoldering, not to damage connection between sides.
Best Regards
glov]]> glov Controllers Mon, 28 Dec 2015 16:04:44 -0500 https://reprap.org/forum/read.php?13,448609,598596#msg-598596 Re: Controller LCD contrast issue https://reprap.org/forum/read.php?13,448609,598596#msg-598596 another thing, can someone explain me the three contrast pins located in top of the memory card reader ??? :S
here is a picture of my LCD please tell me which resistor i should have and where to sold it and thanks]]> aymanem Controllers Sat, 19 Dec 2015 12:26:24 -0500 https://reprap.org/forum/read.php?13,448609,546154#msg-546154 Re: Controller LCD contrast issue https://reprap.org/forum/read.php?13,448609,546154#msg-546154
Purchased from [www.ebay.com.au]

and his advice was "there is a potentiometer beside the LCD,it can adjust the contrast,please try,thanks." yes I had already tried this and makes very little difference.

I said to myself, I mean what can you expect for $13.80 it was a gamble.

I was told to send it back!, like yeah its going to cost as much as the purchase price, that realy is not an option.

Cutting a long story short I read the info here, tried a number of resistors and settled on 560 ohms.

Now the GLCD is very usable and as good as my other $69 GLCD from rerapdiscount.

Regards - bruce

Protective film is still on the GLCD screen.]]> bruce356 Controllers Sun, 16 Aug 2015 00:21:37 -0400 https://reprap.org/forum/read.php?13,448609,529277#msg-529277 Re: Controller LCD contrast issue https://reprap.org/forum/read.php?13,448609,529277#msg-529277
[attachment 57582 DSC_007.JPG] [attachment 57583 DSC_050.JPG]]]> xxkrishxx Controllers Sun, 05 Jul 2015 09:45:38 -0400 https://reprap.org/forum/read.php?13,448609,525625#msg-525625 Re: Controller LCD contrast issue https://reprap.org/forum/read.php?13,448609,525625#msg-525625
- Tim]]> tadawson Controllers Wed, 24 Jun 2015 14:19:13 -0400 https://reprap.org/forum/read.php?13,448609,525553#msg-525553 Re: Controller LCD contrast issue https://reprap.org/forum/read.php?13,448609,525553#msg-525553
[attachment 57116 DSC_0494.JPG]]]> xxkrishxx Controllers Wed, 24 Jun 2015 11:26:08 -0400 https://reprap.org/forum/read.php?13,448609,504257#msg-504257 Re: Controller LCD contrast issue https://reprap.org/forum/read.php?13,448609,504257#msg-504257 iran Controllers Sat, 02 May 2015 05:49:00 -0400 https://reprap.org/forum/read.php?13,448609,504252#msg-504252 Re: Controller LCD contrast issue https://reprap.org/forum/read.php?13,448609,504252#msg-504252 iran Controllers Sat, 02 May 2015 05:15:38 -0400 https://reprap.org/forum/read.php?13,448609,486697#msg-486697 Re: Controller LCD contrast issue https://reprap.org/forum/read.php?13,448609,486697#msg-486697
Quote
the_digital_dentist
I just received a RRD GLCD for my Smoothieboard and found the contrast very low whether powered by USB or 12V supply. After checking a bunch of threads like this one I took a closer look at the GLCD module and found that there is a tiny pot on the back side of LCD board mounted near the edge near the backlight. Unfortunately the pot is designed to be adjusted from above, but above is where the controller board is sitting. Unless you're prepared to bend all the pins that connect the two boards together to get at the adjustment you're going to need some tweezers to grip the rotor of the pot and turn it. I did just that and got the display working perfectly regardless of being powered by the USB or 12V supply.

Thank you for posting this! I just finished soldering the missing LCD interface headers and 1.0A 5V regulator on my Smoothieboard, and was pulling my hair out because the display looked like black letters on a dark blue background. The vendors who copied the genuine RRD GLCD 12864 made an improvement by adding a trim pot on their interface boards to adjust the contrast, but the genuine RRD article does not have that provision except for the inaccessible one on the back of the LCD module itself.

I was thinking about drilling a small hole through the interface board to get at the trim pot until I saw your post. I was hesitant to even try it with a Dremel, because the hole would need to be very close to one of the SD card shield's ground pads. I was able to grab the top of the trim pot with thin needle-nose pliers (power off, of course!), and made a few 1/8 turn swings until it powered on looking just as sharp as your pictures above.....]]> vreihen Controllers Sat, 21 Mar 2015 19:36:34 -0400 https://reprap.org/forum/read.php?13,448609,483807#msg-483807 Re: Controller LCD contrast issue https://reprap.org/forum/read.php?13,448609,483807#msg-483807






]]> the_digital_dentist Controllers Sun, 15 Mar 2015 13:33:14 -0400 https://reprap.org/forum/read.php?13,448609,462075#msg-462075 Re: Controller LCD contrast issue https://reprap.org/forum/read.php?13,448609,462075#msg-462075 codec Controllers Wed, 28 Jan 2015 13:05:24 -0500 https://reprap.org/forum/read.php?13,448609,454801#msg-454801 Re: Controller LCD contrast issue https://reprap.org/forum/read.php?13,448609,454801#msg-454801
Same here.. the Marlin contrast setting has no effect.]]> bobemoe Controllers Tue, 13 Jan 2015 13:28:25 -0500