LCD Replacement for the Macintosh Portable

[Froggy814]

Hello everyone! My portable came to me and I was able to get it fixed. (It has a nice lcd but when it fails I want to be ready, I also want to help the community) But when doing my research so many of them have been turned to parts because of the lcd, it gets worse and worse but cant get better because of little transistors or vinegar syndrome. Well I am trying to modify a design created by Rezafouladian to fit inside of the Portable. It would fit in the battery case or, if best comes to best inside of the display bezel itself.

I have a couple of stages for this project:
Stage 1: Adapter FPC to connect to standard connectors for ease of use connecting to the lcd plug on the motherboard and then putting it to a more standard cable 2x13 2.54 header. Done!
Photos:

Stage 2: Modifying Rezafouladian's design to connect to the 2.54 header. In Progress

Stage 3: Buy it when I have the money and test it.
Extra parts to go with it. An Pi-Zero, and a lcd (that is the right size) with HDMI or av output controller board, cable to connect everything together. (Exhaustive, I know.)

I hope it works and I can share it with all of you when the time comes. I will update progress when things happen. Please share your thoughts and ideas too. Thanks!

-Froggy

 

[Froggy814]

Got all the traces coming from the plug run! They were a pain because they all have to be the same length. I hope they function...



Edit......... I have to reroute them all. The plug is on the wrong side...

 

[Trash80toG4]

NICE! Hopefully the fix won't be too bad.
Though at the frequencies involved in the Portable, do traces really need to be equal for video?

 

[Froggy814]

NICE! Hopefully the fix won't be too bad.
Though at the frequencies involved in the Portable, do traces really need to be equal for video?

Thanks! I hope the fix isn't too bad.

I am not really certain if the traces have to be equal length but just to lean on the safe side I am trying to make them as close to each other as possible. It's quite hard to find anything off the interwebs these days that's useful. (Unfortunant use of AI slop and hard to understand technical pages if you know what I mean)

 

[Froggy814]

Does anyone know why there are grounds and vcc connected to A pins but nothing connected to B pins on the top IC for the A pins? Can I remove one of the grounds to move a D0 to the top IC?

 

[Froggy814]

NICE! Hopefully the fix won't be too bad.
Though at the frequencies involved in the Portable, do traces really need to be equal for video?

Hmm, I guess you're right. I found a trace length difference calculator. The traces can supposedly be off by a little less then 1500mm...
Thank you for making me double check!

 

[Trash80toG4]

Thanks! I hope the fix isn't too bad.

I am not really certain if the traces have to be equal length but just to lean on the safe side I am trying to make them as close to each other as possible.

I have a hunch toat trace lengths became an issue when, or just before alternating ground lines between signals became a thing? Sometime around VLB development on the PC side?

It's quite hard to find anything off the interwebs these days that's useful. (Unfortunant use of AI slop and hard to understand technical pages if you know what I mean)

Nope, haven't even played with AI outside of the assistant on Amazon listings. Besides, I have enough trouble understanding deeply technical things on my considerable collection wood pulp based storage media.

 

[Froggy814]

Nope, haven't even played with AI outside of the assistant on Amazon listings.

I don't mean playing with AI like talking to it and such, I mean all of the web pages that are written by AI which almost always seem to display useless information...

 

[Froggy814]

I have a hunch toat trace lengths became an issue when, or just before alternating ground lines between signals became a thing? Sometime around VLB development on the PC side?

You're probably right about that one!

 

[Froggy814]

Now that I have a rough sketch of the pcb I get into the nitty gritty... WAITING for the Waveshare RP2350 PiZero to show up so that I can take measurements. In the meantime, I will be making the schematic for the Waveshare RP2350 PiZero and (crossing my fingers) hoping I can incorporate it into the final design to make things smaller.

 

[phunguss]

I have a hunch toat trace lengths became an issue when, or just before alternating ground lines between signals became a thing? Sometime around VLB development on the PC side?

I found this an interesting read. https://pcbcool.com/technical-guides/pcb-trace-length-matching-guide/

 

[Froggy814]

I found this an interesting read. https://pcbcool.com/technical-guides/pcb-trace-length-matching-guide/

Wow! That is interesting! Thank you very much!

 

[Trash80toG4]

Very cool indeed. At what level of Mac development did frequencies become "High Speed" enough to require such adjustments in PCB design.

Me likes short and clean!

 

[Trash80toG4]

I will be making the schematic for the Waveshare RP2350 PiZero and (crossing my fingers) hoping I can incorporate it into the final design to make things smaller.

Wondering about your choice of CPU here? The most obvious difference seems to be rechargeable battery power support and then these?

264KB SRAM - as opposed to 512KB SDRAM on Pi Zero, but much faster?
16MB of onboard Flash memory - no memory onboard Pi Zero, MicroSD only there?
reserved solder pads for PSRAM chip expansion - so memory upgrade to Pi Zero's level or more is possible?

Am I reading the spec. sheets correctly. Did I miss anything? Very interesting stuff.
Would these differences make the Waveshare more suitable or less so for Mac Emulation than vanilla Pi Zero?
Does it lack WiiFi support, didn't see that mentioned, that's required for my use case?

 

[Froggy814]

Look!
It all FITS!!!!!! Thats that, we'll just print the pcb and viola!... (JOKINGLY TONE)

No suriously, that is the max pcb size that can fit in the portable's lcd bezel! Now all I have to do is figure out where and how to route traces...

 

[Froggy814]

Wondering about your choice of CPU here? The most obvious difference seems to be rechargeable battery power support and then these?

520KB of SRAM - as opposed to SDRAM on Pi Zero?
16MB of onboard Flash memory - no memory onboard Pi Zero, MicroSD only there?
reserved solder pads for PSRAM chip expansion - so memory upgrade is possible?

Am I reading the spec. sheets correctly? Very interesting stuff,.
Would these differences make the Waveshare more suitable for Mac Emulation than vanilla Pi Zero?

I was just using the waveshare because Rezafouladian's design, (AND CODE, I DON'T WANT TO WRITE CODE IF I CAN HELP IT) Use's that Pi instead of any of the other's. It also seems like a logical choice since it has HDMI out and doesn't have a quad core CPU and it's already really small. It won't have the ram upgrade on my board if it runs fast enough on the output plug though.

Yes you are reading them correctly. I am receiving one hopefully in the week.