Pictorial Vic-20 Fault Guide?

[pms]

For the Commodore 64 there is "The Pictorial C64 Fault Guide" (https://www.pictorial64.com)

Is there anything similar for the Vic-20?
I hoped so because my spare Vic suddenly shows this screen most of the time:
(the other times it just show a black screen)

[Mike]

my spare Vic suddenly shows this screen most of the time: [...]

The VIC registers get initialised, but the screen and colour RAM are not. One possible cause could be a defect in the lower RAM ($0000..$03FF). What happens if you enter POKE36879,26 + [RETURN]? Does the border turn red or do you get no reaction at all? For more troubleshooting you'd need to provide the kind of motherboard (2-prong or CR).

For the Commodore 64 there is "The Pictorial C64 Fault Guide" (https://www.pictorial64.com)

Is there anything similar for the Vic-20?

Denial has the Hardware and Tech section, which explicitly deals with that kind of stuff. There's also Ray Carlsen's repair guide. His home page at tds.net seems to be offline as of today, but here's the latest snapshot by archive.org:

https://web.archive.org/web/20210601074 ... /vic20.txt

[pms]

Thanks @mike !

The VIC registers get initialised, but the screen and colour RAM are not. One possible cause could be a defect in the lower RAM ($0000..$03FF). What happens if you enter POKE36879,26 + [RETURN]? Does the border turn red or do you get no reaction at all? For more troubleshooting you'd need to provide the kind of motherboard (2-prong or CR).

Unfortunately nothing happens when I apply the poke.
It is the Cost Reduced version.
I also noticed that when the Vic is turned on the first time the black screen will be shown.
Even after turning it off/on a few times.

But when it is turned on (and shows the black screen) after 5 minutes the garbaged screen will appear.
Turning it off/on and after 4 seconds the garbaged screen will appear immediately.