rosco_m68k build guide
A Motorola 68010 computer on a single board, built by you from a bare PCB to a boot message. Five soldering stages, lowest parts first, then power-up. The same guide is available as a PDF.
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Before you solder
Tick the kit off against the packing list, then build in the order of this guide. Low parts go first, so the board always lies flat while you solder.
Which way round
Every map shows the component side with the long expansion header J3 on the left. Keep your board that way and "left", "right" and "up" in this guide always match what you see.
You need
Temperature-controlled iron with a fine tip, solder 0.6–1 mm, flush cutters, small pliers, multimeter, masking tape. For repairs: flux and solder wick.
Three parts that can go in backwards
Chips and sockets
The notch marks the pin 1 end. Match it to the notch printed on the board.
Here: every notch points left or up.
Electrolytic caps
The long lead goes in the hole marked +. The stripe faces away from it.
Here: every stripe faces right.
LEDs
The flat edge of the body sits on the flat of the printed outline.
Here: every flat edge faces left.
Every joint
Good
A small cone that wets both the pad and the lead.
Bead on the lead
Solder never reached the pad. Add flux, reheat pad and lead together.
Bridge
Two pads joined. Draw the excess off with wick, then check the gap.
The routine
- Heat the pad and the lead together.
- Feed solder into the joint, not onto the tip.
- Take the solder away, then the iron. Hold still until it sets.
- Trim the lead just above the cone.
Static
The chips are static-sensitive. Leave them in their packing until stage 5 and touch something grounded before you handle them.
Resistors
| Value | Qty | 4 bands | 5 bands | Positions | |
|---|---|---|---|---|---|
| 4K7 | 12 | yellow violet red | yellow violet black brown | R3 R7–R10 R12 R15–R18 R31 R32 | |
| 330R | 4 | orange orange brown | orange orange black black | R1 R2 R13 R14 | |
| 10K | 2 | brown black orange | brown black black red | R11 R19 | |
| 1K2 | 1 | brown red red | brown red black brown | R21 | |
| 2K2 | 1 | red red red | red red black brown | R27 | |
| 270R | 1 | red violet brown | red violet black black | R28 |
How
- Resistors have no polarity. Bend both leads at the body, press the part flat on the board, solder, trim.
- Finish one value before you open the next bag.
Read the bands from the end where they are grouped. The last band, set apart, is the tolerance. Unsure? Measure it.
R7 R9 R10 R12 R15 R17 R18. The CPU socket covers them in stage 3, so they must be in, flat and trimmed first.Small capacitors, crystal
| Part | Qty | Marked | Positions | |
|---|---|---|---|---|
| 100nF ceramic | 22 | 104 | C3–C10 C12 C13 C20 C22–C32 | |
| 7pF ceramic | 2 | 7 | C1 C2, either side of the crystal | |
| 3.6864 MHz crystal | 1 | 3.6864 | Q1 | |
| Button | 1 | S1, top right corner |
How
- Nothing in this stage has polarity. Either way round is correct.
- Seat each capacitor low on the board. Straighten leads that are wider than the holes with pliers first.
- Tape the crystal down and solder it quickly. If a joint will not take, let it cool and try again.
- The button only fits one way. Solder all four legs.
C1 and C2 have three holes for two leads. One lead always goes in the hole nearest the crystal, the other in whichever remaining hole fits the lead spacing.Sockets and oscillator
| Part | Qty | Positions | Which way | |
|---|---|---|---|---|
| 64-pin socket | 1 | IC1 | notch left | |
| 32-pin socket | 4 | U1–U4 | notch up | |
| 24-pin socket | 4 | IC2 IC3 IC5 IC6 | IC2: notch left; IC3 IC5 IC6: notch up | |
| 16-pin socket | 1 | IC7 | notch left | |
| 8-pin socket | 1 | IC15 | notch up | |
| 44-pin PLCC socket | 1 | IC4 | cut corner top right | |
| 10 MHz oscillator | 1 | Q2 | sharp corner bottom left; soldered, no socket |
How
- Drop the socket in, notch over the printed notch. Solder two opposite corner pins.
- Look from the side. Not flat, or notch wrong? Reheat a corner and fix it now.
- Solder the remaining pins. It is easy to skip one in a long row.
The oscillator is a metal can with one sharp corner: that is pin 1, usually marked with a dot.
LEDs, headers, electrolytics
| Part | Qty | Positions | Which way | |
|---|---|---|---|---|
| LED green | 2 | LED1 LED3 | flat edge and short lead left | |
| LED red | 2 | LED2 LED4 | flat edge and short lead left | |
| Header 2×32 | 1 | J3 | two 1×32 strips side by side, short pins into the board | |
| Header 1×6 | 3 | J1 J2 J4 | short pins into the board | |
| Header 1×2 | 5 | J5 JP1–JP4 | short pins into the board | |
| 100µF electrolytic | 7 | C11 C14–C19 | long lead in + hole (left), stripe right | |
| 470µF electrolytic | 1 | C21 | long lead in + hole (left), stripe right |
How
- LEDs first. Solder one lead, check the LED stands straight, then the other.
- Headers next. Tack one pin, check the header is upright, then the rest.
- Electrolytics last, the 470µF at the very end. Push each one flat first.
J6–J8 stay empty: no parts are supplied for them.
Chips and jumpers
First, with the sockets still empty
- Check every joint with a magnifier: beads, bridges, skipped pins.
- Multimeter on continuity across the two pins of
J5. A brief chirp is the capacitors charging. A steady tone is a short: find it first.
Then the chips
- Press each row of legs gently against the bench until both rows are parallel.
- Notch to notch, every leg in its hole, then press down evenly.
- IC4: cut corner to cut corner (top right), then straight down until it sits level.
Jumpers
Leave JP1–JP4 open for the first power-up. Park each cap on one pin.
JP1andJP2power the board from a serial adapter. Never both, never with a supply on J5.JP3enables flash ROM writes.JP4only for the original RAM expansion board.
Power-up
J1 pins, from the bottom up:
- Power. 5 V DC, regulated, at least 500 mA, on
J5: left pin +5 V, right pin GND, as printed on the board. Measure the supply before you connect it. - Serial. A USB serial adapter set to 5 V on
J1(UART-A). The pins follow the usual 6-pin FTDI order, GND at the bottom. With loose wires: board TXD to adapter RXD, RXD to TXD, GND to GND. - Terminal. 115200 baud, 8 data bits, no parity, 1 stop bit.
- Switch on and watch the LEDs.
A healthy board
- LED4, RESET, red: one blink at power-on, then off.
- LED3, RUN, green: on, steady.
- LED2, I1, red: on briefly during start-up, then off.
- LED1, I0, green: blinks about once a second.
On the terminal
___ ___ _
___ ___ ___ ___ ___ _____| _| . | |_
| _| . |_ -| _| . | | | . | . | '_|
|_| |___|___|___|___|_____|_|_|_|___|___|_,_|
|_____| Classic
MC68010 CPU @ 10.0MHz with 1048576 bytes RAMSomething else happens? Unplug first.
- No LED at all: measure 5 V across J5, then check the LED flat edges.
- A chip gets hot: it is in backwards or in the wrong socket.
- RESET stays lit: check IC15, IC5 and the stripe of C11.
- RUN lit, no text: swap TXD and RXD, check the baud rate, check you are on J1 and not J2.
- I0 never blinks: ODD and EVEN ROM swapped, a look-alike chip in the wrong socket, or a leg folded under.
Still stuck?
Send clear photos of both sides of the board to Telegram or solderdemon.official@gmail.com and tell us what the four LEDs do.