LCD replacement trouble

Thread Starter

hide24

Joined Jul 9, 2019
83
Hello,

I have a drum machine which my display has no light and I would like to change to one OLED or LCD 16x2.
The only reference I can get from this original display is that is a SHARP and it’s written HCN-24V.
I tried with some LCD at home but no one will work in this machine.
Anyone know if exists any standard display that could replace this one?
It’s very difficult to see when there is no light , in a dark room.

Thank you very much!
 

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Ya’akov

Joined Jan 27, 2019
5,683
That display uses the HD44780U controller, which is common, but the characteristics of the display will vary with the implementation. You can look online, for example Amazon, but you will have to figure out the size of the display in lines and characters, and the interface type to select a display that will work.

One thing you might check is if the display has a backlight that is not connected. If it doesn't, it would have a white hood on one end of the display (though even if it does if might not be populated).

1644318092692.png

Even if you do find a compatible backlit display you will have to provide power to the backlight and that might not be provided by the existing connections.
 

bassbindevil

Joined Jan 23, 2014
422
Older character LCDs used electroluminescent backlighting which needs high voltage AC from a module, and judging by some 1987-ish Wyse 286 PCs at the office, those modules tended to fail. So if your display is alive but unlit, that could be the problem.
 
Last edited:

MrSalts

Joined Apr 2, 2020
1,762
If your device is older (from the 1990s or early 2000s, it likely has 14 connections (if no back light) and 16 connections with backlight (or edge light).

Pin 3 is typically connected to a trim-pot (potentiometer). This pin sets the contrast and contrast needs to be reset if the LCD has seen temp extremes in its ice time or lots of direct sunlight or if it's just plain old. Check if the 3rd pin is connected to something that has a screwdriver slot. Try turning it while powered up. See if it gets better, worse or not changed. Report back and we can make a plan.
 

Thread Starter

hide24

Joined Jul 9, 2019
83
Thank you very much for the feedback.

I think this LCD never used backlight before, is like the old Yamaha DX7 synthesizers.
Also I haven't seen any cable from the display to the board (if was the case that the backlight was connected)
So, I tried several LCD and another VFD (Which I couldn't see any character appear)

This is 7x2 pin display.
Also I'm wondering if the data sheet of this old display could be very different from standard 16x2 of nowdays?
Unfortunately I couldn't find anywhere...
 

MrSalts

Joined Apr 2, 2020
1,762
Thank you very much for the feedback.

I think this LCD never used backlight before, is like the old Yamaha DX7 synthesizers.
Also I haven't seen any cable from the display to the board (if was the case that the backlight was connected)
So, I tried several LCD and another VFD (Which I couldn't see any character appear)

This is 7x2 pin display.
Also I'm wondering if the data sheet of this old display could be very different from standard 16x2 of nowdays?
Unfortunately I couldn't find anywhere...
So the display is 16 character by 2 rows of characters and it has 14 pins (2 rows of 7), is that tight?

Also, the Hitachi. Chip on the back of your display can handle LED glass with up to 80 characters. If your display doesn't hav 80 characters, the extra characters can be in the buffer (memory) on the display and scrolled. In an case, the hitachi chip makes your display "fairly" standard.

What might be non-standard is the pin numbering. Do any of te 14 pins connect to a trim-pot? If the display doesn't have its own PCB, is there a trim pot close to the hitachi chip? To be exact, is a trim pot connected to a trace that eventual connects to the 8th pin from the left on the bottom edge of the chip (when oriented so you can read HITACHI. If so, turn the pot (it may require a screwdriver. This may increase contrast.
 
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