Otari Status 18R Console LCD Screen Replacement

[burnham]

Hey Guys,

First post here. I'm having some issues with the 2x24 character LCD screen on my Otari Status board. At first, the display would only display useful info over about 1/3 of the display. The other 2/3 were just intermittent lines. Then the intermittent lines went away and that 2/3 turned to blank space. Now, the screen won't display anything, only the backlight works.

The original LCD screen is connected only by a standard 15 lead ribbon cable and IDC connectors. I purchased new ribbon cable and IDC connectors for it but that didn't fix it. My next move was to purchase a similar (seems similar to me) 2x24 display with most of the same connections and swap it out (Optrex DMC24227). All of the Data connections (D0-D7) are there as are R/W, RS, and E.

I'm having a problem identifying what VSS, VEE, and VO match up to. Also, I'm reading that I must use a variable resister connected to VO to control the contrast. How exactly should I wire that up? I've attached a diagram for the LCD as well as the diagram for the digital section of the console that the LCD connects to. Thanks in advance

[Enzo]

I am going to get picky. I bet the screen is not connected by IDC and ribbons, I'd wager the screen BOARD is thus connected. But what about the connection between the board and the glass screen panel itself? I don't know this unit, but many of them have rubber contact blocks along each edge. On the board would be parallel rows of plain flat copper pads. A gray rubber strip runs along atop each row, and that is what the screen sits on. Inside those rubber strips are tiny vertical contacts, lots of them. If the surface gets dirty or skewed out of position, you can lose part of all of your display. Some form of bezel around the glass holds it firm against the rubber contacts.

Does this sound like it might apply to you?

[burnham]

I am going to get picky. I bet the screen is not connected by IDC and ribbons, I'd wager the screen BOARD is thus connected. But what about the connection between the board and the glass screen panel itself? I don't know this unit, but many of them have rubber contact blocks along each edge. On the board would be parallel rows of plain flat copper pads. A gray rubber strip runs along atop each row, and that is what the screen sits on. Inside those rubber strips are tiny vertical contacts, lots of them. If the surface gets dirty or skewed out of position, you can lose part of all of your display. Some form of bezel around the glass holds it firm against the rubber contacts.

Does this sound like it might apply to you?

Thanks for the quick response, Enzo. I believe you're right. The actual LCD is mounted on a printed circuit board, with a rubbery substance in between. I haven't done any disassembly at all. The board was stored improperly for a year but the screen worked fine before being stored. I figured this LCD swap would be simple so I'm trying this before I move on to suspecting other components. I'm pretty much just trying to figure out which wires goes where on the new LCD. When I get to the studio later on I'll snap some pics of both LCD's.

[burnham]

I wired up the new LCD according to some info I found on various sites. The new display showed about 1/3 of the information it's supposed to, similar to how the original LCD behaved initially. This leads me to believe that another component, in line before the LCD, may be the problem. What is the likelihood of one of the 74HC374 chips in the posted diagram being the culprit?

[Jazz P Bass]

I would go back & really clean that 'rubbery substance'.
That is the conductor for the signals.

[olddawg]

I wired up the new LCD according to some info I found on various sites. The new display showed about 1/3 of the information it's supposed to, similar to how the original LCD behaved initially. This leads me to believe that another component, in line before the LCD, may be the problem. What is the likelihood of one of the 74HC374 chips in the posted diagram being the culprit?

Wow... this takes me back. As was stated previously. Make sure you have continuity to the display contacts to the circuit board. After that, start with the basics: Power supplies (Vcc, Vdd or single supply), all your grounds (especially the OC), the clock (right frequency and amplitude?) Check it for the driver u as well. Use a scope. A little canned freeze might be your friend. BUT DO NOT FREEZE THE DISPLAY UNIT! As far as the 74HC374 drivers.... if you have a consistent symptom now you can swap them and see if the other portion activates. Or order one. Probably not expensive.

[olddawg]

And RESET...