Undocumented layout mistake found.

[Bryce]

Hi all,
   does anyone know if the Cost down CPC with SMD Gate Array (Pre-ASIC) Z80330 / MC0100A was ever sold with Centronics ports? I was adding Centronics ports to one of these for someone, but I can't because the pinout is flipped, ie: The row of GND pins is normally on the top row, but on this PCB the GND pins are on the bottom row?? This means that the Centronics port could never have worked cause it's upside down.

See attachments. On a normal CPC the near/lower centronics pins are connected to the lower edge connector pins. On the cost-down the upper centronics pins are connected to the lower edge connector pins. So an edge connector cable would work, but a centronics connection wouldn't.

Bryce.

[TotO]

The costdown was not only the PCB but the engineers.
May be they though it was wired like a "PC" when adding the footprint.

[Bryce]

They may have accidentally put the footprint on the bottom of the PCB and then messed up when they flipped it to the other side. Can happen, but it's usually spotted before it goes to production.

Bryce.

[TotO]

Exactly.

[VintageAdvantage]

Interesting. Is that a 6128 or 464 board? The 464 was never sold with Centronics, not even in Germany. The 6128s had Centronics sockets for expansion and printer and disk, though. I guess, for a 464 board one could claim that it doesn't matter - but then standard flat ribbon printer cables also wouldn't have worked, or?

[Bryce]

It's a 6128 board, 464 boards don't have a floppy drive port, just expansion and printer. The edge connector pinout is correct, so an edge connector flat cable would work. The pin mix-up happens only where the traces go to the Centronics socket.

Bryce.