Tuesday, October 25, 2016
Sunday, October 23, 2016
Here are the two Apple II+ logic boards that I have for repair. They were mostly stripped of integrated circuit chips, and even have some ports and connectors that were de-soldered to repair other boards (back in the 1980's).
I chose to repair the board on the left due to the missing D6 RAM socket on the other board and a possible damaged trace under the F8 ROM.
I swapped the power connector and added a missing audio jack. These are still available on eBay as "panel mount mono jack":
A word of caution. I have found that the solder on these old boards has the potential to make you feel sick and hung-over. Drink some milk before you solder and work in a very well-ventilated area.
I was able to replace most of the missing IC on the board from the box of spares I had, and from the other board. I have no idea if they work, so that will probably require a lot of troubleshooting.
The only IC I could not replace from old pulls was the one labeled "9334" in the J14 position. Fortunately, this IC can be replaced by a 74LS259, which I had on hand from my early experiments with my SPI based Disk II emulator.
Finally, I did not want to have to troubleshoot with old, possibly bad RAM, so I have some 64K 4264 DRAM chips on hand to see if I can replace the original 16K 4116 chips. This will require some modifications to the logic board (due to the different power requirements and slightly different pinouts), which I hope I can complete before the end of RetroChallenge.
Sunday, October 16, 2016
Saturday, October 15, 2016
|The parts donor Apple II+ I am trying to repair is really a mess. Even the rubber feet were harvested for another computer. Fortunately, I found some decent rubber feet on eBay. I bought two packs of 12 20mmx20mmx8mm and it is a great replacement part for Disk II and Apple II feet.|
Regarding my other project, I was pretty scared to connect the repaired IIGS Upgrade board to a power supply, half expecting everything to start smoking. It boots! First time in about 15 years:
|Composite video works||and RGB works!|
Thursday, October 13, 2016
|Trace repairs and new SMT resistors in R193 and R14 locations.|
|Trace repairs and new battery holder.|
|Copper Tape, UV cure Solder Mask, and a weird spatula thing.|
Tuesday, October 11, 2016
- 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.
Wednesday, September 21, 2016
- 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+.
Monday, March 21, 2016
I have an old, un-enhanced Apple IIe that that would give me errors while trying to load disks, like: UNABLE TO LOAD PRODOS or NO BUFFERS AVAILABLE . Now that I know a lot more about the Apple IIe (and electronics in general) than when I put it in mothballs, I tried my hand at fixing the problem again.
I recently leaned that by holding down the closed (filled) apple, while turning on the un-enhanced Apple IIe, it will do a self diagnosis. Here were the results:
RAM: F13 F12 F11 F10 F9 F8 F7 F6
This indicates that every built-in RAM chip was bad (or that the unenhanced Apple IIe can not distinguish which chip is bad). I didn't quite believe this could be true, so I tried replacing some of the ICs around the RAM... to no effect. So, I splurged on an ebay auction for a set of "MICRON MT4264-10 64K 100NS DRAM". I replaced all of the RAM chips, and my un-enhanced Apple IIe sprang to life for the first time in 25 years! As it turned out, only 2 of the RAM chips were bad, but they both failed in a way that would cause the self-diagnosis to report that all of the RAM was bad. Anyway, based on my machine having 2 chips that failed in the same way, I think it must be a relatively common problem.
Now all this thing needs is a "V" key and a replacement key switch. I think the V key is around here somewhere...
Monday, February 22, 2016
I am pretty amazed at the current rate of development of new Apple ][ conveniences and devices. It is worthwhile to look up from a project to see what others are doing every once in a while.
VGA adapters for the Apple IIc and IIGS seem to be hot right now.
The Nishida Radio Disk II adapters are gaining more and more features, including a nice looking web interface!
Big Mess O' Wires had added Apple II support to the Floppy Emu Disk Emulator.
It's impressive to have a microcontroller with more power than the Apple II strapped on the back of it. Although it does feel like cheating sometimes...
I merely managed to find a switch that perfectly fits the Apple II keyboard encoder for enabling lowercase once the character ROM is updated. It is labeled "ONLEDA MTS-202" and is a knock-off of some old high-quality switch, I'm sure. Good ebay search terms : Right DPDT toggle switch. Just take note of how the pins are oriented to make sure you get the right ones. I'm putting mine away for a rainy day.
A new style of Apple II prototyping card popped up on ebay too. Had to buy one.