PS/2 to PCjr Keyboard Converter - Schematic and Source

[jmetal88]

Those look *very* professional!

Thanks! With those two, unfortunately, I'm having some issues with the connectors working themselves loose from the back of the PCjr, so I'm going to try to build the rest of them with the connector sticking out in front of the shielding just a hair. I'm also considering tying to secure the connectors within the shielding using glue or something as they have a tendency to wiggle around inside the shielding, and I've noticed the cables I have put together by IBM (monitor, joystick) don't do that.

I think I've got the timing about as good as I can get it. Mathematically, a preset of 38 on the timer should have resulted in a 220uS time between transitions, but on my oscilloscope, a preset of 38 resulted in times between transitions of slightly longer than that. A preset of 40 looked like it was exactly right, though, so I'll leave it at that.

Now, I do have some final papers I need to finish up for the end of the semester (good grief, I have two weeks left before graduation!), so it might be toward the middle or end of the week before I'm actually ready to start shipping any of these out. The most time-consuming part is absolutely going to be attaching the cables to the connectors and assembling the shielding.

[MikeModified]

Put all your priorities on school; this has no significance compared to completing your major undertaking (although it is a resume builder).

Mike

[Tempest]

Put all your priorities on school; this has no significance compared to completing your major undertaking (although it is a resume builder).

Mike

Don't listen to him, drop out of school and make your living selling PCjr mods. You'll make hundreds!

[jmetal88]

I'm sorry to say it took me 'til the fifth unit to figure this out, but if you wrap the connectors in 1-2 layers of electrical tape before snapping the shields on these go together MUCH more solidly. So if anyone wants to volunteer to buy any of the early four units with connectors that might have issues if they're bumped, you should say so when you PM an order to me. Otherwise, I'll keep my hands on these four and see if I can retroactively implement some kind of fix (like glue) before sending any out.

[jmetal88]

Okay, I got two really solid units together tonight after I got tired of working on my papers, and I also packaged up the best-looking one of the 'iffy' cables. It works, but you have to wiggle the PCjr connector around before the keyboard will power up (it seems to be the most solid if you insert it straight on, then press down on the ferrule just slightly -- it also seems to stay in that position fairly well unless you give it a good bump or have it tangled up in other cables you're moving around). So yeah, there will be four of these that will have to be treated fairly carefully once they're plugged in. I plan on keeping the worst-looking one for myself, as I'd feel awful about selling that one, but the other three at least look decent.

[James]

What would prevent the use of a real PCjr keyboard cable trimmed down?

[jmetal88]

What would prevent the use of a real PCjr keyboard cable trimmed down?

Nothing except that I don't have any.

[jmetal88]

Really, the six with the electrical tape layers inside the shielding should be fine, it's just the four without that will be iffy, which is why I intend not to sell those unless someone asks for one (or until I'm able to rectify the situation, which would probably involve placing another shielding and connector order).

[jmetal88]

Okay, here's what I'm going to do. If you volunteer for one with an iffy connector, you'll get $5 off. So instead of $25 plus shipping, it's $20 plus shipping. But if I get around to fixing them, they go back up to full price.

I am hopefully going to be ready to ship the first units on Thursday or Friday.

[jmetal88]

Oh, I do have one more thing to add:

The PCB fabricator sent me one extra board. I'd sell the board by itself for $5, or I'd put a socket and programmed PIC on it for $10, but you'd be left to attach your own cable, PS/2 connector, two 33pF capacitors, and one 0.1uF capacitor.