Final Push and Failure

I ran jumpers wires on the back of the Apple II+ logic board to route the various signals I needed (PHI_0, AX, A14&A15) to the J1 socket area. Fortunately since only half of J1 is used by the Apple II+, I can use the unused pins of that socket to route my signals through to the new circuit I am adding.

Here is my circuit diagram:

and the adapter board:

Warning - I don't know if this works yet.

After I ran the wires, I started trying to solder a tiny adapter board to translate the 74LS257 signal locations to the new 74LS153 IC. That was taking too much time for something that might not work at all, so I put the circuit on a bread board. Here it is:

Unfortunately, this did not work. I suspect that the dip jumper cable may be too long and adding some capacitance or delay. Or, the RAM timing may have been thrown off by the internal logic of the new IC. My Apple II+ is not booting and is in a similar state to when the RAM was in the wrong row. I'm sure I would have figured this out, but Halloween took priority.

Better news is that my Apple IIb is in a pretty final state. I think I will start buying supplies to actually build it.

Until next time, RetroChallenge!

Apple IIb Model

Added power supply and logic board texture. Color change to be Apple II+ olive-beige rather than Lisa tan-beige.

Apple ][b Refinements

Coming along nicely. I used a more period appropriate keyboard layout, and I think it improved the over-all aesthetics. That's the kind of keyboard I would be using anyway. I am thinking, I might make this an Apple ][b -> IIGS upgrade, since the IIGS logic board is looking so good. I could also use the internals of an AppleColor RGB monitor that I have for the IIGS.

Some Progress, Some Distraction

I spent some time last week working on a Google Sketchup rendition of my hypothetical Apple IIb. The idea is to solve some of the problems with the Apple II+ as a incremental update. It is clear from the Apple II+ design that some of these fixes were deliberately removed from the design late in the process, possibly to keep cost down and possibly because the Apple III was on the horizon. For instance, the odd keyboard decoder arrangement and missing switch clearly contemplated lowercase and a keypad, but the final design did not include either. Here are my specs:

• 80 columns. This is difficult without a full terminal card, which was how most Apple II+s were upgraded.
• Upper/lower case keyboard. Shouldn't be too hard, other than a new character ROM.
• Separate keyboard with numeric keypad. This didn't catch on until after the Apple III, but it should be a relatively easy addition.
• Integrated disk drives.
• Integrated monitor. I'm indifferent here. Although I really think the Tandy TRS-80 Model III and Apple Lisa are some of the best looking retro computers.
• Two serial ports, and a parallel port. This just requires a few expansion cards.

So, mostly a standardized, well equipped, Apple II+ with a few conveniences we have come to expect. Here is my first rendering with elements borrowed from Lisa I and Apple IIe Google Sketchups:

So, that's the progress. The distraction is work on my Apple IIGS Upgrade. Rather than take on another project (Apple II+ logic board), I decided to dive head first into fixing the IIGS. After replacing some of my previous repairs with copper tape, and a lot of soldering, it looks pretty good. The solder mask is curing under UV light, so I will have pictures tomorrow.

RetroChallenge 2016/10 Entry

RetroChallenge 2016/10 snuck up on me due to the new start month. For my entry I would like to focus on the Apple II+.

• First, I want to try to revive an old parts donor Apple II+ which is missing a lot of pieces and ICs.
• Next, I would like to start work on designing the Apple ][b, a computer that could have been released by Apple circa 1979. The b is for business! An incremental release of the Apple II+.