Project: Switch for resetting the serial bus Target : C64 Time : 15 min. Cost : ~1 US$ Use : Revive hung up floppy drive without switching the drive or the C-64 on/off.
Note: It is not a good idea to use a serial bus reset switch
in old C-64s, because the serial bus reset line is directly
connected to the C-64 system reset. This means resetting the
serial bus results in resetting the C-64, too!
In newer C-64s (ASSY/PCB NO. greater than 250407) the serial bus reset line is usually decoupled from the system reset by a diode. On the smaller PCBs (found in C-64 II/c) you might find the serial reset line not at all connected to the system reset.
To find out whether your C-64 can be upgraded with a serial bus reset switch, shortcut pin 2 and pin 6 of the serial bus jack using a piece of wire. If your C-64 resets, you should not use the serial bus reset switch.
Note #2: There are two further variants of the serial bus reset switch: the first one is a reset switch built into a floppy drive (front panel) which is also useful if you want to quickly gain control over your PC-1541 transfer program again after an error; the second variant is a portable reset switch built into a DIN plug for the serial bus jack.