With the basic console working – I guessed the colour fix was likely to be the variable resistor that fine-tunes the colour. Measuring the value of the original in-circuit gave wildly differing values from the expected 500K.
After replacing the resistor and some fine-tuning, the centipede starting screen was back to being purple rather than brown.
The final part of the refurbishment was to complete the composite mod. I decided to use a PCB mounted RCA jack to replace the original RF jack. This was a simple upgrade, only requiring a couple of tracks to be cut to allow the video and ground signal wires to be connected.
With the video sorted, I decided to mount the audio jacks either side – this was a bit of a tight fit, but ended up working well. Not sure I would do it this was gain, the side mounted jacks I used for the first Atari were much easier (and I think they looked better).
Mod complete so I played some more centipede to test – all good. After putting the console back together I noticed that the select and reset buttons didn’t work. This is a common problem with the old Atari keypad membranes – after a little investigation I decided that it was beyond repair :(.
It looks like there will be a part 4 where I fix the buttons……..