Game Gear power mod

[shadow460]

I think I know how to keep the Game Gear and some other portables from blinking off and losing your game progress when you switch from battery power to AC power. What happens is this: As you insert the power plug, a mechanical switch inside the jack switches from battery power to the adapter. It's possible but difficult to stuff the plug in fast enough to prevent a power loss. When you pull out the power plug, the switch goes from AC power to battery power, usually without power loss.

 

So I've bridged the switch contacts. This puts the power jack and the batteries in parallel. It also feeds power to the batteries when the adapter is plugged in, which can be a bad thing. What I'm thinking of doing is simply cutting one of the wires that connects the two battery compartments together and soldering a diode in place to keep the batteries from trying to charge from the power adapter. Granted, I've been able to charge NiCD and NiMH cells this way, but they heat up and it tends to destroy the cells. My goal is to be able to plug in to the wall at will, say when the light starts blinking as I'm about to enter the final stage of Sonic 2 or Shinobi... sans the momentary power loss. I plan to use my standalone battery charger to charge the batteries when they're drained.

 

I also thought of hooking a large capacitor up that could provide power while the plug is being inserted, but I haven't considered yet where it would connect. I've seen this kind of thing work before, though.

[shadow460]

Update: SUCCESS! The power board has solder pads for a diode at D6, but there's nothing there. You'd have to get one with a decent breakdown voltage. I couldn't find any among my electronic scrap, so I chose a different approach.

 

Anyway, theoretically what happens is that when the power adapter is plugged in, D6 acts as a bridge over the switched contacts on the power supply, but it isn't supposed to allow voltage on the battery contacts unless batteries are present. If you bridge the switched contacts, you get roughly 11 VDC on the battery contacts. The traces to D6 do just that, but without anything there, there's no bridge.

 

Enough of that, it's time for modding! I un bridged the switched contacts on the power jack and found a common ground and a spot where you always have +9VDC when the unit is in operation--the power switch. Originally I used a 4700 uF capacitor that Atari had installed in one of my 5200 systems. I had power modded that console, so the 5200 runs fine without the capacitor. That same cap worked here but it is physically too big to fit in the Game Gear. I dug through my parts drawer and found a pair of caps already soldered parallel for a total of 1470uF. They fit in the empty spot at the bottom of the Game Gear just fine. I soldered the positive lead to the one contact on the power switch that's hot when the system is off so the caps stay charged at the expense of draining the batteries over time. You could go to the center lead on the power switch so the caps will charge only when the system is on, but this means it'll be a few seconds until you can hot plug the power brick.

Anyway, the ground I used is on one of the screw mounts on the power board. I smoke tested it with a common game, then put it all back together. It gives me enough time to casually shove the power plug in the jack without losing power to the unit. If I cram the plug halfway in and wait, or if I unplug the power brick with it plugged into the Game Gear, I still lose power, but all I'm after is the ability to hot plug the brick without having to power down first.

 

This mod will work safely for ANY portable system that lacks the ability to hot plug its power supply, and it'll have similar results. The amount of time you have to physically plug the jack in depends on the size of caps used and the system. I imagine that a 4700 uF capacitor installed into a Game Boy Pocket (if it fits) would give you several minutes to slide the plug in or it could even be used to play a quick game or two without power!

 

It's not much, but I guess this makes a classic portable a bit more playable. I'm gonna do my skateboard soon, followed by my Lynx II and my other two Game Gears. The Game Boys have a cheap and dangerous charging mod that tends to destroy batteries, but they use so little power that they can run from the damaged cells with ease. My Game Boy brick doesn't have any mods, but it, too, can run off of the absolute worst batteries I have.

 

DISCLAIMER: NEVER attempt to hook the power brick parallel to a system's batteries!!!!!!!!!!!!!!!!!!!!!!!