Tuesday, 27 August 2019

Punch-Out! pcb repair

This board was mostly working but had a messed up background and no sprites on the bottom screen. The top screen was perfect apart from the missing logo.



Most times powering on the board it also had what looked like an interference issue.


As you can see (just about) the background is now fixed, this was a bad 74LS244 @ 3K on the back / small pcb.

The rest of the issues were on the middle / graphics pcb, first replacing a bad 74LS273 @ 1N brought back glass joe and the main logo.


I also found two 74LS04s with floating outputs @ 1J and 4E replacing these fixed the 'interference' issue.

Replacing two more 74LS273s @ 7H and 8J brought back the player (green guy).


This just left one small intermittent graphics issue with glass joe and the logo flickering and having black lines through them every so often.

I noticed some previous work on the board, someone had replaced the four 74F161s @ 1F,2F,3F and 4F with 74S163s. The one at 1F was rusty and when removing it from the socket one of its pins fell off, I soldered on a lead from a resistor just so I could test it and sure enough it failed.

I replaced all the 74S163s with proper F161s, they seemed to be working okay but I have a bunch of the correct F161 anyway.

In the same area of the board three 74F283s had been replaced with standard 74LS283s, I removed these and installed the correct F (fast) chips to finish off the repair.

I hadn't worked on a Punch-Out pcb before, this is the basic adapter I knocked up. It uses a Mike's Arcade Nintendo jamma adapter to invert the colours and amplify the audio. I basically copied what Adam @onecircuit came up with for his setup. :)


The switches are to flip between top and bottom monitors and the other switches between the two audio channels.

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