Madhatter1

If you have downloaded PCBs, Please update 5/11/22

If you have already order PCBs as I have. I have created an adaptor board. The adaptor has a dual row pin header at top and edge card at bottom. Install pin header on the adaptor then insert through the holes in the SD Drive board and solder to SD Drive board. The pin header will also be used for the optional 32K daughter board. I will be uploading a new SD Drive board to github that will not need the adaptor. I will also upload the adaptor and 32K daughter board.

If you have already order PCBs as I have. I have created an adaptor board. The adaptor has a dual row pin header at top and edge card at bottom. Install pin header on the adaptor then insert through the holes in the SD Drive board and solder to SD Drive board. The pin header will also be used for the optional 32K daughter board. I will be uploading a new SD Drive board to github that will not need the adaptor. I will also upload the adaptor and 32K daughter board.

I've delete the KiCad folder until I get a PCB made. Footprint spacing for the edge card connector is not right. The rows are 100 mil should be 200 mil apart for an edge card. The schematic is right as I have built this on a bread board and has working for me. I was trying to make PCB with Gerber files for others. I'm not putting it back until I have a PCB made and working. The thing is I have already order PCBs I could possible get them to work But I am just going to order new ones.

I've delete the KiCad folder until I get a PCB made. Footprint spacing for the edge card connector is not right. The rows are 100 mil should be 200 mil apart for an edge card. The schematic is right as I have built this on a bread board and has working for me. I was trying to make PCB with Gerber files for others. I'm not putting it back until I have a PCB made and working. The thing is I have already order PCBs I could possible get them to work But I am just going to order new ones.

Note: Make sure you have the latest board 4/26/22. When I changed from KiCad 5 to KiCad 6 the pins got swapped on the side port connector.

Note: Make sure you have the latest board 4/26/22. When I changed from KiCad 5 to KiCad 6 the pins got swapped on the side port connector.

I have uploaded correct files. IO port was backwards.

I have uploaded correct files. IO port was backwards.

I have deleted the schematic. The pins are backwards on the IO port. When I correct it. I will upload it.

I have deleted the schematic. The pins are backwards. When I correct it. I will upload it.

I have added PCB layout and Gerber files for the TI-99/4a SD Disk Project.

Added PCB layout and Gerber files.

I just want to clarify the chip you need is 74LS540. There is no change in board for TI-99/4a SD Disk Project.

I think the chip your talking about is the 74LS540 inverted buffer. The schematic originally showed a 74LS541 non inverted buffer. Both chips have the same pinout. You can use the same board. I have been using this board for about about 3 years without a problem. I wire wrapped mine and didn't make a PCB. When I changed the chip I forgot to update the schematic. You could also correct it in the firmware by adding an invert instruction. As I originally done due to TI sending data inverted.