Repairing Atari C-140 Super Pong console - Notes & Comments

[WimWalther]

I know there's some crossover interest between Atari 8-bit and the early game consoles, so I might as well put this here. I'll try to be brief.

C-140 Super Pong works, but RH paddle is very erratic and the unit often resets or fails to tally the scores. Paddle issue fixed with normal cleaning of the control pot, easy. Fixing the (intermittent) scoring issue was more difficult.

Fyi, the circuit board can be removed without a soldering iron - remove the pair of tamper-resist screws inside the base, remove the paddle knobs, nuts & washers, separate the case top half and unplug all the connectors. Now the board can be taken out for work. If like me you lack the proper bit for the tamper-resist screws, you can JB Weld #4-40 nuts to the heads and then remove with a 1/4" nutdriver once cured.

Now the repairs..

There are three parts in the "push start game" circuit, which is also responsible for resetting scores - C14 (1 nF), R12 (100K) and S1 (NC start switch). Most importantly, despite what both available schmatics indicate: SWITCH S1 IS A NORMALLY CLOSED SWITCH. This had me chasing my tail for a while.

Elsewhere it was said that this scoring issue was fixed by replacing C14 & R12. I replaced C14, but my unit had no R12 - so I added it for good measure as I assumed that pin 20 of the LSI chip wasn't being reliably pulled-up. Ultimately, the switch was at fault and replacing it solved the scoring issue.

That about covers it, maybe more later.

 

[WimWalther]

I'm still trying to understand the reason for the presence of R12, or lack thereov. At 100K it seems too high in value for an effective pull-up. So then maybe it forms an RC time constant with C14? But again, R12 seems to be deleted from the build on later units.

So I suppose it's possible thst the LSI used in Super Pong has an internal pull-up on that pin, and they're still using the same board as the earlier units.