RetroWiki

There are two different power supplies depending on the age of your VIC-20. The oldest is a simple 9VAC power adapter with two prongs (on the VIC-20 side). The other is around connector similar is shape to the C-64's.

If you have a rando spare 9VAC @ 2-3Amps power adapter keep it as your backup power supply for your VIC-20. Some interesting tidbits are at https://forums.atariage.com/topic/226541-vic-20-power-supply-replacement/

A 5VDC and 9VAC power supply. When they fail they can fry your beloved C-64. The earliest models are encased in epoxy. Some of the slightly newer models are repairable. If you plan to throw away the power supply because it is old and you don't want it to fry your or someone else's C-64 - that's fine but please cut the power connector side off. Cut it off right next to the power supply so there is a long power line and C-64 connector. People want these.

You can use a C-128 power supply on a C-64 if you change the end connector. It provides a heavy duty power supply for the C-64.

A DC and AC power supply. Here are some details on the US model.

You should NOT use a C-64 power supply on a C-128. It does not provides enough consistent power for the C-128 and the poor quality of the power supply could fry your C-128, the same as the C-64.

Model name: DSP-128 Part number: 310416-01

Output ratings:

• 5VDC @ 4.3Amps
• 9VAC @ 1Amp

Input rating:

• 117V 60 cycles 70VA

Fuse:

• 1.6A @ 250V
• accessibly from the bottom without opening the case

If you plan to throw away the power supply because it is no good, please don't. Hackers want the square power connector, the power supply is repairable, and if the guts are completely shot there are internal replacement units people put in the old case.

These rock because there is a built-in power supply - just like a REAL! computer.