Gp2X Power Switch Fault.


coldfish

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Dec 20, 2006
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Not sure if this has been noted before, correct me if it has.

I've recently discovered something interesting about my GP2X.

When I run Battery test and touch or lightly press the power switch, the battery life remaining will fluctuate from ~100% down to ~60-70%.
Sometimes it will start lower and go up to a higher value. The switch still has a positive click when switching on and feels normal.

My impression is the switch has faulty contacts and may be acting as a resistor, draining power.

So far Ive cleaned the switch with iso-alcohol and reheated the solder pads, this has improved it a bit but I can still nudge the switch and get a response (up or down) in Battery Test.

I wonder if this is contributing much to poor battery life? I suppose I could test by shorting the solder pads with solder and seeing if battery life suddenly improved dramatically.


It'd be pretty dumb if it turned out that a lot of people experiencing low battery life was because the power switch was faulty.
 
Battery life is guestimated by checking the voltage from the battery compartment via a 10-bit ADC reading. The extra current draw of the switch shorting between the on and off positions will temporarily drag down the voltage and so you'll see a difference in the battery life meter.

The ADC reading isn't exactly very accurate, as any changes in current draw can affect its results, so it's just a rough guide.
 
Do you think a faulty switch could have a significant effect on battery life in this case?

I know it can with simple circuits like torches etc.

I imagine the switch in the GP2X isnt connected to the battery directly but through the power circuit where it switches a transistor which opens the flow?
Though, if this is the case a faulty switch probably shouldnt cause any change in battery test, just on or off.
Does that mean that the switch is directly connected to the batteries, seems a small switch for the large current the GP2X draws, I wonder if it's up to the task? Also, I notice the switch is anchored only by its solder pads with no chasis mounting - erk.

ps, my electronics knowledge comes from years of practical experimentation, not theoretical study - so I could be barking up the wrong tree / neighborhood.
 
There is a fault in the GP2X power connector that can radically decrease battery life .. do a search for 'reset power connector' in the GP2X archives, its pretty well described and can be fixed with a paper clip ..
 
coldfis said:
Do you think a faulty switch could have a significant effect on battery life in this case?

I know it can with simple circuits like torches etc.

I imagine the switch in the GP2X isnt connected to the battery directly but through the power circuit where it switches a transistor which opens the flow?
Though, if this is the case a faulty switch probably shouldnt cause any change in battery test, just on or off.
Does that mean that the switch is directly connected to the batteries, seems a small switch for the large current the GP2X draws, I wonder if it's up to the task? Also, I notice the switch is anchored only by its solder pads with no chasis mounting - erk.

ps, my electronics knowledge comes from years of practical experimentation, not theoretical study - so I could be barking up the wrong tree / neighborhood.

I don't know if this would be related, but whenever I come across a colecovision I have to radically clean the on off switch or it causes all kinds of trouble (presumably because the dirt/corrosion is changing the voltage level). I also noticed that my gp2x is very, very sensitive to batteries and once 1/2 drained no longer work in it. The battery connectors aren't very good either.

Chris
 
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I definitely get the impression the faulty switch was wasting power. Battery Test now shows them with 100% when fresh charged instead of hovering around 80ish.

I'll have to look for a similar one and solder it in.
 
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