On 04/02/2017 08:51 PM, drlegendre . wrote:
If the unit was otherwise working as-found, then it might be safe to say that whatever +was+ under that button +must+ have either disintegrated or fallen out of place, yet evidence should remain. In either case, you should find evidence - crumbled, gunky old foam, or shrapnel of a busted plastic / rubber spring. Point being, if it hasn't been opened up (to repair) in the past, everything should still be inside, at least in some form.
Well, it seems that there isn't supposed to be anything! The metal plate is dished and is supposed to deform when the reset switch is pressed, making contact with the PCB, and then returning to original shape when the case switch is released. Except that - which is the case with mine - it seems that they have a habit of deforming slightly over time (and also coming loose, potentially shorting out various components and causing damage).
Bending the tabs which are supposed to hold it against the PCB at least made it secure, but it still wouldn't return to original shape after being pressed. So, I figured I could hunt around for a replacement plate from a donor console, and *maybe* it would be OK, and *maybe* it would last for a few years. But in the end it seemed better to implement a more robust solution: it just so happened that a standard miniature microswitch (the type with four pins, dpst) would fit nicely onto the PCB, with the pins - after a little bending - sliding through the PCB slots which used to retain the original metal plate. A couple of short jump wires to nearby PCB pads later, and electrically it was perfect.
The downside to this is that I had to shorten the stem on the plastic case part of the reset switch by ~ 1/8" to compensate for the increased height of the microswitch, and I really don't like "destructive" mods. However, I figure the rework will easily last the life of the console, and at least there's no risk of things coming apart and damaging the logic now. I suppose Mattel would have spent the extra few cents on a real switch anyway if the design life of the console had been more than a few years :)
cheers Jules
