Whats in the box?

VIC-20 Diagnostic Cartridge: Custom circuit board with a reset button on top so you can restart the tests without switching off.
Cassette port loopback dongle
User port loopback dongle
Keyboard loopback dongle (fits the keyboard connector on the motherboard)
Control port loopback dongle
Serial port loopback dongle

Professional-Grade Commodore VIC-20 Diagnostic Suite

NEW from Any Retro!

Name: Commodore VIC-20 Diagnostic Cartridge & Test Harness Set
Brand: AnyRetro
Price: 39.99 USD
Availability: InStock

Everything you need to quickly and completely test your beloved Commodore VIC-20.

In addition to the Diagnostic Test Cartridge that completely tests the inner workings of the computer, this set also includes all the necessary dongles to test the external ports.

Multiple diagnostic tests per component include:

Zero Page
Stack
Internal Ram
External Ram (if present)
Screen Ram
Character Rom
Basic Rom
Kernel Rom(s), including PAL/NTSC detection
JiffyDOS compatible
VIC chip specific tests
Color Ram
Casette Port
User Port
Serial IEC floppy port
VIA1
VIA2
IRQ/NMI tests
Sound tests

Advanced memory testing algorithms

Go deep to find RAM memory faults:

March C- — w0; r0,w1 up; r1,w0 up; r0,w1 down; r1,w0 down; r0. Catches stuck bits, transition faults, and address-decoder faults.
Solid patterns — $00, $FF, $55, $AA, each written then read back.
Address uniqueness — low byte of the address stored in each cell, then the high byte. Catches aliased or shorted address lines.
Walking ones — $01, $02, … $80 written and read at every address. Catches stuck bits and bit coupling.

Compatibility

Works with PAL and NTSC VIC-20s and detects which one you have.
Works with original KERNALs and JiffyDOS 6.01 (PAL and NTSC).
Works on a stock, unexpanded machine. Tests 3K and 8K expansion RAM if you have it fitted.
No disk drive, tape deck or software needed. Everything runs from the cartridge.

How to use it

Switch the VIC-20 off.
Plug the cartridge into the expansion port, and fit the loopback plugs to the ports you want to test.
Switch on. The tests start straight away.
Watch the screen. After each full pass it pauses for a couple of seconds and starts again. Leave it running as long as you like to soak-test the machine.
Press the reset button on the cartridge to start over.