Adding EPROM sockets to your Juno-106
What's the deal?
Later Juno-106 models have masked ROM inside the CPUs instead of external EPROMs. The PCBs however are the same, so there is an empty spot on the PCB for the EPROM and a jumper to select which memory to use (External=EPROM or Internal=CPU masked ROM). On the module (voice) board there is also a 40H373 circuit missing so you'll need to add that one as well.
CPU Board
See picture below.
1. Remove (cut and discard) the resistor at jumper position (I) (Internal) (1)
2. Add a jumper wire at jumper position (E) (External) (2)
3. Add a 28-pin socket for EPROM (3)
Click for larger image
My modded CPU board with added EPROM socket and jumpers changed. I also replaced the battery and fitted a battery holder.
Click for larger image
Module (voice) Board
See picture below.
1. Remove (cut and discard) the resistor at jumper position (I) (Internal) (1) <
br/>
2. Add a jumper wire at jumper position (E) (External) (1)
3. Add a 28-pin socket for EPROM (2)
4. Add a 40H373 IC (3)
Click for larger image
My modified module board with EPROM fitted, jumpers changed and 40H373 mounted
Click for larger image
Back: To my main Juno-106 mod page
