Faulty VIC

[Gaia]

Hi all, it's been a while since I posted on this forum. I have dusted off my good old VIC20 today that used to be in working condition the last time I fiddled with it (around 2017 I believe). To my horror it no longer boots up properly, looks like some part of the circuitry or one of the IC's went bust I am greeted with the usual albeit blank screen and a blinking cursor and I can type text (that suggests to me that the VIA's, the CPU and the VIC are all working). See attachment. Upon pressing RETURN however, the computer deadlocks... every once in a while the deadlock is already happening right after booting.

Any guesses what the culprit could be? I am suspecting a RAM issue here but I might be wrong. At any rate, at least not one of the more precious IC's are defect...

[srowe]

Could be a bad BASIC or KERNAL ROM. Do you have a games cartridge to test?

[Gaia]

That's a very good idea! I have a Cosmic Cruncher cart somewhere in the attic... gonna go ahead and dig it up... let you know how it went. Faulty ROM would be the "best" option as that's the only socketed IC

[Gaia]

Aaaand.... it works! Yay... so it's the ROM then. Alas, I have double checked and only the KERNAL (901486-07) seems to be socketed, the BASIC ROM (901486-01) - that is the likely culprit here - is soldered

I fired up my Ebay account to check for a replacement and was shocked how expensive these are... :-O
https://www.ebay.de/itm/385532872307?mk ... media=COPY

[srowe]

There was a seller in the UK that had a batch of new old stock at a reasonable price. When I return home I'll find the link. Desoldering a big chip requires some skill not to damage the tracks. If you're not confident yourself perhaps you can find a local enthusiast to help you.

[Edit found the link not sure if they ship to Europe]

https://www.ebay.co.uk/itm/403435259173 ... media=COPY

[Gaia]

Thanks! A local friend of mine offered me help although the replacement ROM might be an issue for him, so cheers for the link!

[JonBrawn]

Remember to socket the new ROM...

[Gaia]

Small update: it was indeed the BASIC ROM, turned out this friend of mine had a replacement chip after all. And thanks for the tip, it will be socketed