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Old 22 October 2019, 09:39   #1
wairnair
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More power for usb mouse adapter via shorting a resistor?

I got me a usb mouse adapter. Works for a few seconds then stops working. I was told to short R352 to provide a bit more power for the adapter.


Now, my thinking is that on system power-up this will cause a short between 5V and ground until the capacitor C352 is saturated and breaks the connection. Is this correct?

Could this damage components inside the CD32 or a connected joypad?
R352 was put there for a reason after all I guess (limit current to roughly 1A instead of short?).



Anyone with some electronic skills please comment. Thanks!




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Last edited by wairnair; 22 October 2019 at 10:23.
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Old 22 October 2019, 10:54   #2
hooverphonique
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Well, yes and no.. storage caps (like c352) are placed across power rails without a resistor in almost any digital electronics design you will come across, so is normally not a problem. The PSU and pcb traces should be designed to handle the inrush current for the storage capacitance.

In practice you won't get a 1A current limit since the voltage would've dropped to 0.3V volts @ 1A. The resistor is there to protect the CD32 if shorting 5V and GND on the mouse port. You could measure the voltage on your usb adapter to see if it is indeed due to the resistor that it doesn't work, then either short it or replace with a smaller value.
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Old 22 October 2019, 11:05   #3
wairnair
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Quote:
Originally Posted by hooverphonique View Post
You could measure the voltage on your usb adapter to see if it is indeed due to the resistor that it doesn't work, then either short it or replace with a smaller value.

It's 4.91V vs. something very close to 5V (like 5.05V I can't remember exactly) that I measured a few months ago on the riser.


So shorting the resistor can't do any damage as long as the joypad doesn't short 5V and ground - which it doesn't. I'll give it a try then, thanks.
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Old 22 October 2019, 11:40   #4
hooverphonique
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Quote:
Originally Posted by wairnair View Post
It's 4.91V vs. something very close to 5V (like 5.05V I can't remember exactly) that I measured a few months ago on the riser.

I'd be surprised if the adapter or pad would struggle working correctly at 4.9V, but it could be the case, of course.
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Old 22 October 2019, 14:03   #5
Hewitson
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I wouldn't recommend shorting it out. It's a current limiting resistor, removing it from the circuit could cause a fire if you happened to have a controller/mouse that had malfunctioned...

Quote:
Originally Posted by hooverphonique
I'd be surprised if the adapter or pad would struggle working correctly at 4.9V, but it could be the case, of course.
Agreed. Extremely unlikely.
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