Sunday, 17 November 2013

Rusty VIC20 Restoration

Sometimes it seems you can never tell what you're going to get from ebay. This was one of the one was a candidate for a USB Keyboard, it looked to be a nice, non-yellowed VIC20.
The thing which identified this as a candidate was seen in the photo of the rear of the unit.
Oh dear, looks like this has been sitting in water and the screws had rusted
I was expecting this to be over the whole board, and the thing would be a write off, and therefore just a thorough clean of the case and keyboard, and ready for the USB board.
However, it seemed to be limited to the edge of the board, to the screws and the metalwork.
I wondered if it could be saved, so I took out the board and had a go with a solution of vinegar and water.
It seemed to clean up very well, so I removed the metalwork and a few discrete components and cleaned up the rest of the board.
Most of the board cleaned up quite well. I later reflowed the solder on those tracks to get rid of the remainder of the corrosion.
The metalwork was quite corroded, so I replaced it with a shield from a scrap board.
Now that all the corrosion had been cleared up, I was back with a VIC20, ready to test.
Black screen. Oh dear. Well, now onto the usual VIC20 repair routine. Nothing was running hot (apart from the VIC as usual), reset was happening, the clock was running, and the keyboard was being scanned. So I hooked up a 1541 disk drive and tried some 'blind' disk commands. So even though the screen was showing nothing, typing

LOAD "$",8

resulted in disk access. So this was going to be an easy one. The machine was running, just the display that wasn't happening. So, it was the VIC or the possibly the video memory. Neither of those were socketed, so I tried the VIC first, removing the old chip and replacing it with a socket and a known working chip
Powered it back up and voila, one ready screen.
After that, it was onto giving the case a good clean and sorting out the rusty end panel.
All reassembled, it cleaned up rather well.
It's one of the whitest VIC20's I've seen
A nice addition to the collection