This is a replacement board for the Signetics 2519 chip used in the Apple-1 computer.
It is based on the work of Szillat and P-LAB, so I stand on the shoulders of giants:
- Szillat's 2519 replacement
- P-LAB's 2519 replacement SMD
As of 2024, the 2519 has only a single source (and I think that this has been the case for a very long time). With shipping, that single chip would cost over USD 85.
This board is a drop-in replacement for the original chip, and uses more modern and available 14557 shift registers. However, note that it is designed specifically to fit on the Apple-1 board, by straddling two chip sockets:
- the 2519 16-pin DIP
- the 7400 14-pin DIP to its left
- this is unused on an Apple-1 with the 6502 CPU
- however, it is used on this board to provide stability and ground
The small-package SOIC-16 14557 chips used by the existing boards are not available from major electronics components stores (or only in very large quantities). When I built P-LAB's SMD version, I had to buy the chips on eBay, and they are not reliably available there either. However, the Wide SOIC-16 chips are easily available. So this board is a simple redesign to support the wider chips. I managed to do this without making the board larger, partly by putting all the decoupling capacitors on the bottom side.
- V1.0: Initial version. I assembled one such board and it's been working fine.
- V1.1: Version with fatter +5V traces, additional via for decoupling capacitors.
- I HAVEN'T TESTED THIS VERSION YET.
- 2025-01-02: I got a report from someone who tested this successfully :)
| Quantity | Item | DigiKey Link | Mouser Link |
|---|---|---|---|
| 1 | 2519 Replacement PCB | N/A | N/A |
| 6 | 14557 Shift Register | DigiKey - MC14557BDWR2G | Mouser - 863-MC14557BDWR2G |
| 6 | 0.1uF Capacitor (0603) | DigiKey - C0603C104K3RAC7082 | Mouser - 80-C0603C104K3R7082 |
| 1 | 16-Pin Header | DigiKey - 220-1-16-003 | N/A |
| 1 | 14-Pin Header | DigiKey - 220-1-14-003 | N/A |
This information is provided as-is, with no warranty. I have tested it on an Apple-1 reproduction, and it works for me. However, I cannot guarantee that it will work for you. I am not responsible for any damage to your Apple-1 (reproduction or original) or other equipment that may result from using this board. I am especially not responsible if you try this on an original Apple-1 and it doesn't work or, worse, destroys your priceless computer. Use at your own risk.