AC30

SWTPC AC30 Reproduction

A reproduction SWTPC AC-30 Cassette Interface

Description

I have a couple of Motorola MC6800, MC6802, and MC6809 machines from the 1970's. And I wanted to setup a typical cassette player/recorder setup to save and load code written on these machines.

Note: 2026/10/11 - I hate the way Claude built the human readable schematics. A lot of net lists instead of a nice arrow to the net list. Anyway, so after a bit of double checking I've ordered 5 SMT boards and we'll now see the quality of the designs.

2026/10/11 - The schematics are now drawn with real wires, block by block, instead of a label on every pin. Readable PDFs and PNG images of every sheet and functional block are in kicad-smt/schematic/ (SMT) and kicad/schematic/ (through-hole), for example the SMT modulator:

2026/10/10 - Both boards (through-hole kicad/AC30 and SMT kicad-smt/AC30_SMT) now wire the front panel (switches, LEDs, motor jacks, MIC A/B and EAR A/B jacks) to labeled through-hole wire pads instead of the J1/J2 Molex connectors. Board details are in AC30-settings.md and AC30-SMT-settings.md; the parts list is docs/AC30-BOM.md, with Kicad BOMs in kicad/AC30-BOM.csv and kicad-smt/AC30_SMT-BOM.csv.

Board sizes are now 173.0 x 126.5 mm (6.8" x 5.0") through-hole and 173.0 x 88.5 mm (6.8" x 3.5") SMT. Gerbers and drill files for both boards are ready for the board house: kicad/AC30-gerbers.zip (through-hole) and kicad-smt/AC30_SMT-gerbers.zip (SMT, including the top paste layer for a stencil). kicad/tools/build.sh regenerates them on every build, or run kicad/tools/gerbers.sh (add smt for the SMT board).

The SMT board also has a pick-and-place position file, kicad-smt/AC30_SMT-top-pos.csv (SMD parts only, mm, origin at the board's bottom-left corner), to go with the BOM for an assembly house. The through-hole board's layout was re-placed so a fresh build routes completely again; the build now tries other placements automatically if routing ever comes up short. Both boards now have a GND copper fill on both layers (thermal reliefs on the GND pads, so they're still easy to hand-solder; details in the settings files above), added automatically by the build after routing. The motor and relay lines (MOTOR_1A/1B/2A/2B, RELAY_1/2) now use the same 0.6 mm tracks as the power rails, good for roughly 1.5 A. Known issues, including what to check before ordering boards, are listed in KNOWN-ISSUES.md.

2026/10/09 - I've update the PCB to add the mod/demod circuits and a Molex for the power. Additionally I had a new SMT version created.

2026/10/08 - This is my first go around with Claude, Kicad and FreeCAD and creating a PCB to be sent off as Gerbers. I have a lot of inspecting to do. But for a 1st go this is scary impressive.

Claude created Kicad files

I gave Claude the following prompts:

Create a kicad schematic for docs/AC30-BOM.md docs/ac30_schematica.jpg

and

Save what you have but provide solder pads and labels for the missing power and mod/demod

and

Now create the pcb from the schematics. Minimize the board size but leave a safe boarder along the edge.

After this I use a few suggested prompts.

Here's what the inside of the Original SWTPC AC30:

I'd estimate the board to be about 9" x 9" (inches) in size. Here's the schematics I gave Claude:

I gave it the AC30/docs/AC30-BOM.md file (simple markdown text file).

Claude started churning and created a 'schematic' (doesn't look like the above, hard to read) and I imported it into the PCB editor. Then didn't make any changes. Instead I let Claude do the rerouting.

I then found out I needed to upgrade Kicad to 10.7 and FreeCAD 26.3 so Claude could create Python 3.11 scripts to build a schematic, the PCB and routing. That was messy as I have Debian Trixie and the latest wants Debian Forky. Anyway, this is the final 1st round attempt. More cleanup to do yet before I ship off the Gerbers.

I'd estimate the size of the new PCB to be about 3.5" x 7" (inches).

So after several hours, including the Kicad/FreeCAD SNAFU, those are the results. The TPx are where I just dumped a bunch of jumpers I hadn't decided on. I'll fix those later. While it's not done it's a huge jump. It would have taken me about two weeks to get all the parts on the schematic, connections defined and PCB routed.

Credits

I stole this from Deramp's AC30 (Mike) site. And he saved it from Mike Holley's original SWTPC site.

Links

• Deramp's AC30 page