I'm not 100% sure of the pinout for the serial port, but I've seen tapping
off of ports to provide additional power to external devices. Like the
Cardco Card?+G parallel printer interface has a connector with a single
wire that plugs into the cassette port for extra power. I've seen people
instead run this to pin 7 of the game controller port of C64's, etc., to
keep the cassette port free. So, maybe its something similar.
On Fri, May 11, 2012 at 4:03 PM, Kevin Reynolds <tpresence at hotmail.com>wrote:
I was going through my vintage machines collection and happened to notice
something strange with a commodore plus/4 I have.
On the right side, there was an additional RCA connector that I had never
seen before this.
Opening it up, it appears to only have a wire jumpered from one of its
connections to pin 6 on the serial port.
I can't imagine why someone would do this. Any ideas?
Pictures are here.