LCD Rainbow - Page 1
Forum section: electronics / projects

author: bostonman
author_rank: Super Contributor
timestamp: April 23, 2023, 01:17:58 pm
content: The LCD on my 3D printer began showing a rainbow type display (see attached).Is there a way to fix this?

author: AndyBeez
author_rank: Frequent Contributor
timestamp: April 23, 2023, 01:53:11 pm
content: It might be a failure of the polarizing filter or, heat/impact damage to the liquid crystals. Replace with a new 20x4 LCD.

author: bostonman
author_rank: Super Contributor
timestamp: April 23, 2023, 01:57:18 pm
content: It never saw heat or impact. It was in my basement and seemed to just occur one day when I powered the printer.

author: Ian.M
author_rank: Super Contributor
timestamp: April 23, 2023, 02:34:41 pm
content: One common problem with the ANET3D LCD2004 board (which you appear to have) is printers with laser cut frames or display mounts often don't have long enough spacers between the display board and back plate avoid bending the display board, and its possible that the display board has been pressing on the back of the LCD module. If so, shim the back plate with extra washers on the mounting screws between it and the PCB so the soldered pins are NOT pressing on the back plate, and file out the front and back plate mounting holes if they are mismatched to the LCD2004 mounting holes (which also bends the PCB). With luck, once you remove the pressure/bending the LCD *may* slowly recover.Tweaking the LCD's contrast control voltage may get a bit more life out of it. On an ANET3D LCD2004 display board, the contrast voltage is set by the R2:R3 potential divider, located on the back of the board near pin 1 of the HD44780 4x20 LCD connector. Remove them and kludge on a 10K preset, wiper to pin 3 (VO), one end to pin 2 (Vcc) and the other to the ground plane. Twiddle for best compromise contrast across the whole display. If you get an acceptable result, you'll need to mod the backplate (or fit much longer spacers) to permit reassembly. If if doesn't give a usable improvement you'll need to replace the LCD, either by desoldering the 16 pin SIL header connecting it to the display board and fitting a new HD44780 4x20 LCD (4 line 20 character), and refitting R2 and R3, or by simply buying a new ANET3D LCD2004 display board, clones of which are readily available on Amazon, eBay and the usual far east eBazaar sites.

author: bostonman
author_rank: Super Contributor
timestamp: April 24, 2023, 01:32:08 am
content: I tried loosening the screws (although they didn't appear to be applying pressure to the LCD) and it didn't make a difference.This LCD doesn't have that many hours use. I've probably printed fifteen items, and, if each one took an average of 2.5hrs, that's less than 40hrs.Is the replacement one you recommended the actual part because you're familiar with the one used on the Anet A8 or does any generic one work?

author: Ian.M
author_rank: Super Contributor
timestamp: April 24, 2023, 01:47:39 am
content: After removing mechanical pressure, I wouldn't expect it to recover quickly, if it recovers at all. It could take as long or longer than the fault initially took to appear. Power on hours aren't relevant here if its pressure damage.Clones of the Anet3D LCD2004 display board are widely used on cheaper Prusa clone 3D printers + some others. My familiarity with it is due to its use (together with an ANET3D v1.5 controller board) in my CTC DIY i3 Pro B 3D printer. Seehttps://spiritdude.wordpress.com/2018/03/26/ctc-diy-prusa-i3-ctc-diy-i3-pro-b-most-affordable-3d-printer-2018/(not my blog). I was considerably more nitpicky than that blogger regarding looming cables neatly, checking preassembled subassemblies, and general fit & finish and adjustment issues, which is how I discovered the display assembly was warping the LCD2004 PCB!To the best of my knowledge, Anet3D LCD2004 display board clones are interchangeable. Worst case you might have to file the mounting holes slightly if they are poorly aligned. HD44780 4x20 LCD modules are more of a mixed bunch as the size, mounting hole positions and connector placement are not standardised, however the form factor used on the Anet3D LCD2004 board seems to be far the commonest. Check dimensions carefully before ordering!

author: james_s
author_rank: Super Contributor
timestamp: April 24, 2023, 02:00:38 am
content: The easiest way is to replace the whole display, it looks like a standard off the shelf HD44780 type LCD. You can even get OLED versions that are electrically and mechanically compatible if you want to be fancy.

author: bostonman
author_rank: Super Contributor
timestamp: April 24, 2023, 02:14:21 am
content: QuoteI assume this would last much longer?Do you happen to know any part numbers that have the same footprint and can easily replace the old one?

author: Ian.M
author_rank: Super Contributor
timestamp: April 24, 2023, 04:47:19 am
content: Don't expect an OLED to last longer - they have finite shelf life and organic LED light output typically decreases faster with operating hours than other types. Good quality LCDs are pretty durable - I have one HD44780 2x40 LCD salvaged from an '80s laser printer that is still in good working order and getting on for 35 years old.

author: rdl
author_rank: Super Contributor
timestamp: April 24, 2023, 05:06:53 am
content: I have a Newhaven 4x20 LCD that's been in almost constant usage over 10 years. It's lost a bit of contrast but still readable. I haven't bothered to fiddle with the contrast. You can get nearly if not exactly drop in Oled replacements for LCDs. I have a 2x16 in blue, also from Newhaven, that looks absolutely amazing, better than VFD actually. Supposedly they can suffer from burn in. I haven't used mine that long.

author: james_s
author_rank: Super Contributor
timestamp: April 24, 2023, 06:16:16 am
content: Quote from: Ian.M on April 24, 2023, 04:47:19 amThey don't last longer, they just look really slick. I've had a couple of cheap OLED displays fail but I've also got some with quite a few hours on them that are still fine.For long life it's hard to beat LCD, I don't think I've ever had one of those character displays fail.

author: bostonman
author_rank: Super Contributor
timestamp: April 25, 2023, 02:31:33 am
content: QuoteIs this the better replacement choice or should I continue looking?

author: james_s
author_rank: Super Contributor
timestamp: April 25, 2023, 03:32:29 am
content: Quote from: bostonman on April 25, 2023, 02:31:33 amIs what? There are zillions of different HD44780 displays, the HD44780 was a LCD controller developed by Hitachi back in the 80s, now there are countless different clones, most of them are fine, the common sizes can be just a few dollars. Most are the same footprint and pinout.

author: bostonman
author_rank: Super Contributor
timestamp: April 25, 2023, 04:57:31 pm
content: I didn't realize clones exist.I thought this was one type, but could vary in size.

author: james_s
author_rank: Super Contributor
timestamp: April 25, 2023, 05:05:49 pm
content: I don't know if the original Hitachi controller is even still made, I think most of them are clones. At any rate HD44780 is the controller, any display that uses it or a compatible part has the same electrical interface and responds to the same commands. Most are in a more or less standardized form factor with the pins in a row along the top, there is another type with a double row of pins on the end. A display that is 2x16 means two lines of 16 characters, 4x20 means 4 lines of 20 characters and so on.

author: rdl
author_rank: Super Contributor
timestamp: April 25, 2023, 05:13:29 pm
content: I would suggest if possible to buy a quality replacement. Or at least make sure it's easily returnable. I've gotten some really poor low priced displays. Slow to update, poor contrast, pixel ghosting, etc. I had one I tried to use where part of the display was a six digit clock. The seconds display was unreadable. My go to supplier is Newhaven mostly because Mouser stocks them, but their displays are good. I also like Microtips, but I haven't bought many of those.

author: Ian.M
author_rank: Super Contributor
timestamp: April 25, 2023, 05:16:21 pm
content: Sometimes you see a character LCD with a non-standard pinout. The 14 power, control and data pins for the HD44780 (or compatible) controller are almost invariably standard, with the same numbering, in either the SIL or (more rarely now) the two row format, but the backlight A and K pins can be elsewhere, e.g. in front of the pin 1 end of the 14 pin group, rather than as pins 15 and 16 after it.Also 4x40 displays are different - due to limited display RAM and matrix size support of HD44780 (compatible) controllers they are actually organised as two stacked 2x40 displays with separate controllers, sharing all pins except for Enable, and thus have a different pinout.

author: horsepork
author_rank: Newbie
timestamp: January 26, 2024, 05:15:18 pm
content: Ian, I think I am dealing with a non-standard LCD like you've described, but I cannot wrap my head around what the pinout could possibly be.K goes to what is labeled as pin 1, and A1 goes to pin 14. 5V across A1 and K turns on the backlight. A2 goes to pin 16, and I am not sure what its function is.The LCD is from an old cash register, and the model number is not showing up online anywhere unfortunately. Any pointers? And apologies if this would typically warrant a new post. Just created an account and wasn't totally sure on protocol.

author: Buriedcode
author_rank: Super Contributor
timestamp: January 26, 2024, 10:17:24 pm
content: That is indeed a non-standard part - not sure why you posted it in a thread about a damaged 3D printer LCD. Perhaps a new thread would be better.