As described in the “Junior Computer revival history” topic I started todesign a new PCB. I wanted to stay as close to the original as possible , with the original “Digitasten”, even though they start to become hard to obtain and are quite expensive. I called it version V2.0 as I considered the original Elektor Junior to be V1.0.
Where have I deviated from the original design :
I changed the 2708, 1K Eprom to a 2732, This avoids the need of 3 supply rails (+5V, +12V, -5V) and only requires a single 5V., 4K Eprom.
Note : Due to a design flaw the Eprom requires to be fully filled with a 4*1K image (4 copies of the monitor in the 4K Eprom).
Design error #2 :
When drawing the schematics I think I went a bit too much on “auto pilot” and later on the 2nd check I missed this.
/CS1 of the 6532 should be connected to A9 and not A8.
On the PCB this this can be corrected by :
- Remove the trough-hole plating with a slightly larger drill.
- Isolate the top-layer with a piece of Capton tape.
- Run a small wire from A9 to pin 38 of the 6532.
See the two clickable pictures below :