So I've got this C64 that I came across some years ago that exhibits a number of odd problems. I set it aside as a pet project (no pun intended) to work on should I come across a spare C64 to gut for chips.
That time has now come. This past weekend I was able to purchase (rather cheaply) a C64 with a dodgy power supply but otherwise working. As luck would have it, like my sick C64 with odd errors, this C64 has socketed chips and is the same board revision and everything (both 1984 models, and this board: http://upload.wikimedia.org/wi...d_1984.jpg
). So I'm ready to go to work. Since I'm not handy at all with a soldering iron (indeed I don't even own one), but I can manage slotting in and pulling out chips, I figure it best to take the good chips out of the C64 with the dodgy power supply, and use them to repair the strangely-behaving C64.
However, before I go screwing around here replacing chips all random-like, I thought it prudent to hop on here and give a decent description of the problem so as to narrow down the (possibly) offending chips without needing to replace each and every one of them on the board, but also not screwing up both machines so that neither is in a non-operable state.
The first major symptom with the sick C64 is its sound. Only one of the sound channels plays correctly. The other will make noise, but has no volume control, and indeed the notes will stick "on" on that channel. The third channel does not sound at all.
The second problem, most apparent after playing around a bit, is the colors of the characters on screen do not behave properly. On bootup, the screen appears normal (light blue border, dark blue interior with the usual C64 BASIC message across the top, and the READY message). However, when trying to programmatically change colors using a simple POKE command, sometimes that works and sometimes it does not. Also related to the graphics issue, some sprites will not appear. So, for example, if I play a game like Donkey Kong
, instead of the correct colors showing, I get an almost entirely red primate at the top. Also, the barrel colors don't appear correct either.
Now, with my bare minimum knowledge about the chips and how they interact and all, I'm guessing this might be caused by a busted SID and VIC-II. But I wanted to confirm all that on here first before I go playing around with my machine to get more insight on the matter.