Problem with RAMPS and MEGA 2650

Hi all. I'm new to the forum but I've had my A8 for a couple of months and immediately bought a Pi 3 model B and obviously the boards I mentioned in the subject. My problem is that I am not getting any text on the display. It gets power but nothing else. The brightness adjustment works and I have the correct definition (RepRap discount smart controller) enabled in Marlin. I have triple checked all wiring and connections. Thought I might have fried a voltage reg when I put limit switches on wrong pins and applied power. Not sure I did though as the printer still acts the same way. After buying new RAMPS, MEGA and A4988s, still nothing. I read on this forum that there is a resistor that is needed for the display itself. I was under the impression that the resistor is only needed if the adjustment for brightness does not work. Am I wrong? If photos are needed, I can upload. TIA Dan

P.s. Is it possible to run this particular setup without the display? I use Octoprint for controlling everything except for leveling. That will be for the BLTouch I have.

Personally I like the 3D printers LCD Displays. Using the standard setup to run 3D Printers with Octoprint, You really do not need the LCD display though.

On the "RepRap discount smart controller" purchased it was labeled as contrast. The problem with my Hictop compatible ramps 1.4 controller running the RepRap discount smart controller,
was that most of the connectors pins were inverted, making the display blank. After inverting the cables the display worked. Is it possible you have the connector plugged in backwards on the ramps.
Or the cabled were made incorrectly inverting the pins.




Top row Images, the Two LCD have a different connector that inverts the Key.
Bottom Image the Single Image with two LCD I have remade the cables to correct the Connector key inversion.

KEY = the notch in the connector to prevent the cable from being plugged in backwards.

Not saying this is the problem just putting out information that could help you.

Edited 4 time(s). Last edit at 06/03/2018 09:46AM by Roberts_Clif.

I have tried the cable fix (cables made correctly) and get nothing. I have also checked for the hidden pot on the back of the display board, but I was not able to locate it. So I am guessing that I will have to try a 560 Ohm resistor. Its either that or do away with the display altogether. I like having the jog dial and the fact that I bought the stupid thing and I want to use it. I am getting frustrated. But I guess that comes with this hobby.

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GSD
So I am guessing that I will have to try a 560 Ohm resistor. Its either that or do away with the display altogether.

At $10.00 for a display I would just buy another and complain about the original for a replacement. (2 Kits and never had problems getting defective parts replaced!!!)

It does come with this hobby. I have an LCD that has a defective SD reader from day one.
A power supply that blew the thermal fuse on the first day (most likely a defective/and underrated thermal fuse as it melted), replaced with a jumper wire, had a pigtail fuse in series working now 2 years.
Replaced power supply supply fan with a full ball bearing precision fan much better that the original.

Your talking about a common patch and hidden pot normally found on a glcd, but have set "RepRap discount smart controller" which is a 2004 char display

Are you 100% sure you have a "RepRap discount smart controller" looks like the following


Or a "REPRAP_DISCOUNT_FULL_GRAPHIC_SMART_CONTROLLER" looks like the following

I have the 2nd one pictured and it is defined in Marlin. I even recompiled to make sure. I read somewhere in this forum that there is a hidden pot on the rear of the board the lcd is mounted to but i wasn’t able to see one. I am gonna try the resistor fix and if that doesn’t work I am going to just forego using the display and use either Octoprint or Pronterface for control. I was using Octoprint before I started the Bowden conversion. Then maybe I will shell out MORE money for a new display. Think I might opt for a better one though.

Edited 1 time(s). Last edit at 06/03/2018 09:29PM by GSD.

@Roberts_Clif Can I ask where you purchased fan and about how much it cost you?

Edited 1 time(s). Last edit at 06/03/2018 09:28PM by GSD.

If the GLCD does have the hidden pot, its normally impossible to get to and normally behind a component on the back pcb so you can even drill for it.

The resistor fix works well, I've had to apply a few. It just adjusts the contrast up a bunch,

How are you powering the mega currently? via power to the ramps?
If you think may have damaged the voltage regulator on the mega plug the mega into the computer via USB cable, leave external power off. This provides 5v to the mega and GLCD from USB power and bypasses the regulator.. (You can't run it like this, but its a good test) If GLCD now displays stuff ... regulator issues.

Please take pictures and post your configuration.h so we can double check everything.

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GSD
@Roberts_Clif Can I ask where you purchased fan and about how much it cost you?

With the death of all the Electronics parts stores (Radio shack, Radar, ect.....) in my area the Only place I shop is E-Bay the only place that guarantees receipt of online merchandise or a complete refund.

Yeah, I’m in the same boat. I live in SE WV and there is nothing but a Walmart and Lowe’s and they don’t have anything. I shop Amazon and have never had problems with refunds/replacements and with prime, I get stuff quick with free shipping. Once bought an MJX 101 (quadcopter) and camera didn’t work. Instead of sendin me a new camera, they sent a whole other MJX 101 with a camera plus refunded me $15 for my trouble. So I got 2 of them for $35.

Thanks for the help guys. It was a U8glib.h issue. Having another issue now.