The other day I was thinking about the 20k resistor that I didn’t have – and got to thinking. “Can’t you run resistors in series or parallel to adjust the net value?” I thought to myself. So, I called my dad as I thought that if you put them in series you then added the ohm rated resistance values together.
I have an 18k, and I have some 1k’s – I need a 20k… So, I soldered the selected ends together (after calling my dad to verify) and put them in. Hoping against hope – I put the board in the machine and gave it power.
I had the machine where the LED (which indicates boot status success/failure) to be constantly on. I counted this as progress.
Tonight though I had some more time
So, I re-verified all the continuity points for my U8 IC on the MPU. And of course found a number that needed to be updated.
If you are a follower/reader you know that I recently determined there was more corrosion damage than I had originally thought (in my haste). So, I spent the past few times that I’ve had free to remove that, and install a socket for the U7 chip.
After this process the LED got through the flicker and first flash. YAY – there needs to be 7 successful flashes for the game to boot up as each one indicates a phase completed.
Energized with my success I realized that I had not verified continuity on the U7 socket that I had replaced. And remembered belated that there was a trace that had evaporated in the corrosion cleaning phase under U7. I found one leg of the IC completely isolated from the game – figured what points it needed to connect to. Verified each of the other 21 legs on the chip – and after 2 hours of testing and soldering I decided to hold my breath and plug it in again.
Watching the LED like a hawk – it flickered. Then flashed… once.. after a bit of a pause it flashed again, and again, and again, and again, and again, and again – and then there was a sound sequence, and the scores lit up.
The game is now in the same playable state as it was when I received it – but it not longer has the battery leaking more corrosive gasses and destroying the game. It now really looks like a Frankenstein machine with trace wires crisscrossing all across the back. It isn’t pretty, but it is working – and I didn’t have to spend $200 to replace it. I can live with not so pretty when no one will see it unless they pull the board out of the game.
Now.. time to run down the switch problems… (next post)