Bwack's RetroComputer Adventures

After playing with a C64 i picked up recently and the disk drive that came with it, I notcied that loading failed once in a while.. It was not the disk or the drive, because by trying the drive on my other C64 the drive works. I read online that on the Serial Bus there are buffers with open collector output (7604) and they fail often. I replaced one and, Voilá !

SID chips fail all the time and especially the filters fail often. One SID chip is not equal to another. Been experiensing various weirdness with the audio from the C64. Audio seems very sharp but some games sid tunes sounds as if a channel is missing. However the case is not that simple. Listen to the track at about 9 minutes in. Nice and crisp synth sound however the bass lead is missing.. You can hear the same tune but with propper filtered bass lead recordded from a good SID chip here at 6:28: My video above also has a track of Jeroen Tel Robocop. To me it sounds fine. Great Giana sisters is missing some parts of the audio and the wind noise in the very beginning of the game is gone. In the image below I've used a BASIC program called SIDBench , and all channels and waveforms seem fine except when filters are switched on. Below you can see three recordings of audio from running SIDbench on several chips.. Recordings are lined up in Audacity and view mode is Spect

Welcome to my first blog post. This blog will cover my repair and mod adventure of old computers. Mostly the C64. Computer architecture will be discussed later where I look at a simple cpu starting with the accumulator. We will build it with descrete components and make so slow that we can see and feel where information is moving.. This is my first videoe where I brought my trusty old Commodore 64 out of the cupboard, and inspect it for capacitor leaks and corrosion. The RF moduler has been ruined once in the 80s, but no need for that in 2015. The RF output is repurpose as a composite output with a simple modification. The modulator gets a wire from Composite signal to the RF RCA connector. The RF signal was cut from the board.  The pcb and traces in the middle of the pic shows some signs of corrotion, but I'm not sure. However there is exposed traces there. Couldn't find corrotion here, but these caps might need replacing soon. In