Search found 4 matches

by DoctorOctal
Wed Sep 21, 2022 2:02 am
Forum: Design Ideas 💡
Topic: ADLIB/MPU-401 Expansion bay
Replies: 7
Views: 6467

Re: ADLIB/MPU-401 Expansion bay

TexElec now has an Adlib card for the PCjr.
by DoctorOctal
Sat Apr 04, 2020 9:34 pm
Forum: Parallel Side Car
Topic: Parallel Port Side Car items
Replies: 17
Views: 11722

Re: Parallel Port Side Car items

I may write formal instructions some day but am far from that point right now. I haven’t even touched my own parallel port yet, there are other things I need to investigate before I do, I have other projects competing for my time, etc. I just wanted to point out the unused NAND gates I saw before yo...
by DoctorOctal
Sat Apr 04, 2020 1:01 pm
Forum: Parallel Side Car
Topic: Parallel Port Side Car items
Replies: 17
Views: 11722

Re: Parallel Port Side Car items

Just out of curiuosity, did you try driving the LED from the first gate , LED and Resistor to ground. Should be enough drive to light the LED and get rid of the second gate ! Brightness ? Todd already tried sourcing the LED current, and it worked for him. I imagine it would work for others, too. I ...
by DoctorOctal
Sat Apr 04, 2020 10:57 am
Forum: Parallel Side Car
Topic: Parallel Port Side Car items
Replies: 17
Views: 11722

Re: Parallel Port Side Car items

FYI, all the gates you need are probably on the board already. I looked for spare gates on the schematic in the PCjr technical reference and only saw one NOR gate available. However, when looking at a board I have on hand as well as photos of other parallel port boards, I see a 74LS00 quad NAND chip...