This is my first post here for a while but it’s quite long so deserves it!
A short while ago I acquired a VIC 20 for the price of postage (thanks Johnny Blanchard – Re:Enthused) but it didn’t work so I bought one from eBay.
I used this to start some diagnosis. After a few chip swaps I discovered the 6502 wasn’t working so I bought a replacement and it was up and running, but it didn’t recognise when a disk drive was attached.
Using a borrowed oscilloscope I did some diagnosis and concluded that one of the outputs of the 7406 inverter chip wasn’t giving any signal, so I ordered a replacement and some sockets.
This arrived today so I piggy backed it over the suspect ship and the disk drive was recognised!
As I knew it was bad I wasn’t worried too much about damaging the failed 7406 but I did want to try to remove it cleanly… I failed. 3 pins just wouldn’t clear.
A mangled (but failed) 7406 IC
I then soldered a socket onto the board and popped the replacement 7406 in and all is good!
I did manage to break off the electrolytic surface mounted capacitor from the SD2IEC (floppy drive emulator) so had to do some more research and diagnosis to figure out which way around it fits then did my first ever surface mount soldering, and it all still works!
My SD2IEC – the capacitor is to the lower left of the SD slot
The small 14 pin 7406 in a fresh socket and the screen showing a directory successfully loaded proving the repair is successful is shown below. This is my first deep diagnosis and repair of an old computer and I’m quite happy with the process and especially the results.