13 Button On Board Computer SCREEN repair ideas?!

[paynemw]

NO I don't have a fix, but I want to start a discussion about it and I'm not looking for "just replace it." Let's get fucking technical here, education is key and it's the 21st century, there has to be a solution to the screen "bleeding" issues we all face with the 13 button OBC.

So since getting my e30 up and running again, I replaced the back light with the Garagistic LED thing, and the light bulb for the buttons has been replaced. And I've finally found a 3.1.2 coding plug. Now one thing I've noticed is that it's not widely known that you need to make sure the coding plug you have correlates to the model you have. Now I have a early M20b25 car... so 55L and 6 cylinder and b25... so I can't use the coding plug for same year M20b27 cars and I can't use the 4.6 coding plug that like 90% of the e30 community uses because that accounts for the 63L fuel tank.



But I got this mint OBC - but it has bleeding. So I started to wonder if I could find a way to repair the screen. I've sold two OBCs but what I'm noticing is that everyone's getting rid of them because they bleed, so naturally the supply is running down. And coding plugs, don't get me started.

I've seen the DIY screen repair for the e36 OBC but who can hook it up with a company that could sell a replacement screen? Garagistic? BavRest? e30ig.com?

[bmwman91]

So the bleed in the 13 button OBC, as shown in your pic, is due to either the liquid crystal cells being broken and leaking, or layers in the LCD delaminating and leaking. There really is no fix, at least not for the LCD panel itself. The E36 failure is due to lousy electrical contact between the flexible connector strips and the LCD terminals, which is why putting in a "spacer" helps to fix it. It's a totally different failure mechanism.

I have actually disassembled a 13 button OBC and probed the display communication lines and stuff. It is very unlikely that a drop-in replacement exists on the market, either because it was custom made for this, or because it has been 20+ years since it was made. The only real option would be to find an 8 digit LCD that fits in the spot properly and to custom make a new logic/driver board to display the data. The communication protocol used by the OBC motherboard is really pretty simple. But, someone has to actually design, program and fab the new logic board for a new LCD. One idea I have had floating around in my head for years is to rebuild the entire electrical system in the OBC from scratch to have more features and accuracy and to eliminate the stupid coding plug entirely. The circuit in that thing is going on 40 years old, and I bet that ~75% of the guts in there can be replaced with a single modern microcontroller.

I have a bunch of other projects on my plate now, but I might (MAYBE) be able to look into this at some future time. Anyone else with he time and skills is welcome to jump in.

[paynemw]

bmwman91 - yea I took apart the OBC today and took some pictures along the way. It looks like the OBC was somewhat designed to have replacement parts. Atleast the We can separate the problematic part. But like you said, who knows if there is a replacement part on the market. That's what I'm looking for. Someone to produce a replacement screen assembly!

The OBC comes apart at this seam, but you must remove the two screws on the back of the OBC.


The back cover comes off around the green plug. This is what you're left with once you pull the back cover off:


Next up, preparation to separate the faceplate from the motherboard. You can use needle nose to pull these from the posts:


This part sucks, I actually cut my finger pulling the motherboard off of the faceplate. You have to pull pretty hard, and wiggle back and forth to get them to separate.


Now that the motherboard has been separated, there are 7 screws that hold the screen assembly onto the faceplate. I used a small electronic/jewelry philips to remove them.




Damn you broken screen...


two filters go between the screen back and the backlight area:


I can't really make it out, but there's a stamp on the back of the screen assembly:


Now who can I ship this bad bitch to who can figure out how to reproduce one?

[litu]

i´am very interest this also...So sub

[e30davie]

You wont fix the lcd. I had a bit of a google around. The lcd looks custom for the job. Big numbers and small numbers. Ive got no idea what functions are on it, but replacing it with an aduino and a gineric lcd would be a fun project. All doable (ive played with arduinos a fair bit). But youd have to be pretty keen to go to that much effort.

[earthwormjim]

That display is entirely custom, you will not find an off the shelf solution. Best you could do is salvage a known broken OBC with a good LCD.

An Arduino is overkill and quite large, an 8 bit processor could be used to drive a modern LCD display, interpreting and converting the signals from OBC. A PIC microprocessor would work well, they can accept higher voltages too.

[hoveringuy]

My OBC doesn't work. Again....
I don't even want to bother replacing it with a used replacement because I'm convinced that given the amount of electronics in these things, the replacement would be on borrowed time.
I will throw the challenge out: Someone design a retro-OBC that uses form-factor of the old one, but with a PIC that replaces the 30+ year old electronics, and an OLED display that can have oil temperatures and such.

Here's an example: https://www.sparkfun.com/products/11677

If we could have a 2018 version of the OBC, what features would it have? I couldn't really care about average speed and such. Personally, I would make a CANBUS repeater for parameters on my Megasquirt.

[paynemw]

You wont fix the lcd. I had a bit of a google around. The lcd looks custom for the job. Big numbers and small numbers. Ive got no idea what functions are on it, but replacing it with an aduino and a gineric lcd would be a fun project. All doable (ive played with arduinos a fair bit). But youd have to be pretty keen to go to that much effort.

Oh yea, I mean I have no idea how I would do it, but I'd love to see if there is a company who'd be willing to do it.

[bmwman91]

For the cost of a custom LCD unit in a small quantity, you could probably buy a new M3. The design and tooling to fab an LCD part, even one as seemingly simple as this, have significant cost associated with them. Then again, maybe you could find a factory on Alibaba to do it, but I would be surprised.

Finding a genericLCD, either 8 digit or a dot matrix, and then driving it with an Arduino or PIC which intercepts the mainboard's signals seems more likely. IIRC, the protocol that the existing controller uses involves a clock and 160 bits of data with each bit corresponding to one of the individual display segments. I may have the logic analyzer captures at home somewhere. The other 3 pins are 5V, ground and a 256Hz square wave which I believe is used to de-bias the charge on the LCD segments so that charge build-up does not cause the segments to all become opaque, but this is not likely to be needed if you go with a new LCD module since it will either be built in to the controller or just not necessary since we have 30+ years of technological advances.

[bmwman91]

For the cost of a custom LCD unit in a small quantity, you could probably buy a new M3. The design and tooling to fab an LCD part, even one as seemingly simple as this, have significant cost associated with them. Then again, maybe you could find a factory on Alibaba to do it, but I would be surprised.

Finding a generic LCD, either 8 digit or a dot matrix, and then driving it with an Arduino or PIC which intercepts the mainboard's signals seems more likely. IIRC, the protocol that the existing controller uses involves a clock and 160 bits of data with each bit corresponding to one of the individual display segments. I may have the logic analyzer captures at home somewhere. The other 3 pins are 5V, ground and a 256Hz square wave which I believe is used to de-bias the charge on the LCD segments so that charge build-up does not cause the segments to all become opaque, but this is not likely to be needed if you go with a new LCD module since it will either be built in to the controller or just not necessary since we have 30+ years of technological advances.

[rreims]

LCD replacement

You really do not believe it but you can buy new screen from Germany shop www.partworks.de .

Just swapped my OBC screen and it is really working!

[jgilber0]

DAMN! That's great! I wish I had known about it before I swapped mine for a used unit off of ebay.

[Stanley Rockafella]

hmm, considering getting one as a backup.."just in case".
IIRC, the screen has never been replaced on mine. Is this something that'll ultimately go on me? kinda like SI board batteries?

[Todd Black 88]

hmm, considering getting one as a backup.."just in case".
IIRC, the screen has never been replaced on mine. Is this something that'll ultimately go on me? kinda like SI board batteries?

Yes. I put 3 in my M3 in 12 years. All failed at some point. Leaked when I sold it.

[jeffnhiscars]

You really do not believe it but you can buy new screen from Germany shop www.partworks.de .

Just swapped my OBC screen and it is really working!

I like this...now if I only read German. I assume there's a shipping charge and did you contact them in English ?