Junior computer
About the Junior computer PCB
Junior computer is an open source PCB design by laurent-fr, published on GitHub under the CC-BY-NC-4.0 license. It is a 2-layer board measuring 217.2 × 113 mm, with 80 components from 50 distinct parts.
Other key parts include the 6522, 2114, 2716, NE565 and LM311. By type, the board carries 25 switches, 23 resistors, 13 capacitors, 11 ICs, 5 connectors and 3 diodes.
It belongs with the retro computing designs in this gallery.
From the project
A replica of the Junior Computer (a KIM-1 clone) published by Elektor in the 80's
The Junior Computer is a 6502 SBC made by Elektor in 1980. It looks a lot like a KIM-1.
This is a replica PCB I made with KiCAD.
The best source of information for this computer is Elektor Magazine from 80's , but you can find a lot on this website : http://retro.hansotten.nl/6502-sbc/elektuur-junior/
This board is not a 100% accurate replica, because I have added directly on the PCB a few updates published later by Elektor : a fix for memory decoding needed for the expansion board the main decoupling capacitor C2 was on wrong side of S25 (activate display) which could reset the computer *…
Main components on the Junior computer
Junior computer bill of materials (BOM)
80 components, 50 distinct parts — part numbers from the project's BOM.
| Qty | Part | Footprint | Refs |
|---|---|---|---|
| 1 | 6522 6502 | DIL-40 | IC1 |
| 1 | 2114 2716 | DIL-24 | IC2 |
| 1 | 2114 6532 | DIL-40 | IC3 |
| 2 | 2716 2114 | DIL-18 | IC4, IC5 |
| 1 | NE565 74LS145 | DIL-16 | IC6 |
| 1 | LM311 74LS145 | DIL-16 | IC7 |
| 1 | LM311 NE556 | DIL-14 | IC8 |
| 1 | 74LS241 74LS00 | DIL-14 | IC9 |
| 1 | 74LS241 74LS01 | DIL-14 | IC10 |
| 1 | 74LS243 ULN2003 | DIL-16 | IC11 |
| 1 | CONN_01X03_SOCKET Display | Conn-Display-Bottom | J1 |
| 1 | CONN_01X03_SOCKET C64AC | DIN-41612-AC | J2 |
| 1 | CONN_01X03_SOCKET DIN41617-31 | DIN-41617-31-F | J3 |
| 1 | CONN_01X03_SOCKET Conn_01x03_Female | Jumper-D-EX | J4 |
| 1 | Conn_01x03_Female | K4-K6 | J5 |
| 1 | RST | Digitast | S1 |
| 1 | ST | Digitast | S2 |
| 21 | Switch | Digitast | S3, S4, S5, S6, S7, S8, S9, S10 +13 |
| 1 | STEP | SW-2T | S24 |
| 1 | DISPLAY | SW-1T | S25 |
Show 30 more
| Qty | Part | Footprint | Refs |
|---|---|---|---|
| 2 | 1N4148 | Diod-4 | D1, D3 |
| 1 | 1N4148 LED | Digitast-LED | D2 |
| 1 | 220N 10p | CAP-2 | C1 |
| 1 | 47µ 6V | CAP-POL-5 | C2 |
| 1 | 22N 100n | CAP-3 | C3 |
| 1 | 100n | CAP-3 | C4 |
| 1 | 6N8 1µ 16v | CAP-POL-2 | C5 |
| 2 | 6N8 1µ 16v | CAP-POL-3 | C6, C7 |
| 1 | 100N 1µ 16v | CAP-POL-1.5 | C8 |
| 1 | 47N 1µ 16v | CAP-POL-3 | C9 |
| 1 | 1µ 16V | CAP-POL-2 | C10 |
| 2 | 1µ 16v | CAP-POL-3 | C11, C14 |
| 1 | 470n | CAP-2-HEX | C12 |
| 4 | 3k3 | Res-5 | R1, R2, R3, R4 |
| 1 | 22K 4k7 | Res-5 | R5 |
| 1 | 10K 330 | Res-5 | R6 |
| 2 | 8K2 68 | Res-5 | R7, R8 |
| 1 | 4K7 68 | Res-5 | R9 |
| 2 | 10K 68 | Res-5 | R10, R11 |
| 1 | 6K8 68 | Res-5 | R12 |
| 1 | 2K2 68 | Res-5 | R13 |
| 2 | 10K 3k3 | Res-5 | R14, R15 |
| 1 | 100 3k3 | Res-5 | R16 |
| 1 | 330 2k2 | Res-5 | R17 |
| 1 | 4K7 68k | Res-5 | R18 |
| 1 | 470 2k2 | Res-5 | R19 |
| 1 | 1K2 68k | Res-5 | R20 |
| 1 | 15K 1k | Res-5 | R21 |
| 1 | 4K7 1k | Res-5 | R22 |
| 1 | 4K7 820k | Res-5 | R23 |
Junior computer design files
The KiCad project lives in the laurent-fr/junior_computer_replica repository on GitHub; these links point at the commit this page was built from.
Junior computer: common questions
How big is the Junior computer PCB?
The Junior computer measures 217.2 × 113 mm, has 2 copper layers and is 1.6 mm thick.
How many components are on the Junior computer?
80 components, from 50 distinct parts, with part numbers taken from the project's own BOM. The full bill of materials is listed on this page.
Where can I download the Junior computer design files?
From the laurent-fr/junior_computer_replica repository on GitHub, which has the KiCad layout and the BOM; the links under Design files point to each one.
Can I use the Junior computer design in my own project?
It is published under CC-BY-NC-4.0, which limits how it may be reused; read the license before building on it.
More boards in junior_computer_replica
Junior interface
217.2 × 113 mm116 parts2LCC-BY-NC-4.013
Junior computer - Copie
204.5 × 104.1 mm77 parts2LCC-BY-NC-4.013
Junior universal memory
160 × 100 mm38 parts2LCC-BY-NC-4.013
Junior bus
116.8 × 100 mm13 parts2LCC-BY-NC-4.013
Junior interface conn
91.4 × 19.7 mm9 parts2LCC-BY-NC-4.013
Junior computer display
77.5 × 31.8 mm7 parts2LCC-BY-NC-4.013
Ram adapter
34.3 × 33 mm5 parts2LCC-BY-NC-4.013
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