Atari switcher test load (?)

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Hi;
I am working on an Atari switching P/S and was wondering what would be a good load (?ohm resistor) to test the P/S with?
The reason for my question is that while hooked up to the PCB, I read +5.27vdc on the PCB which leads me to believe it is in run-away protection mode. I want to troubleshoot the P/S without further damaging the PCB but without a proper load, I will not be able to test it.
Thanks in advance
Jeff
 
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You'll need V=IR and/or its friends, I=V/R & R=V/I

Figure the PS likely designed to supply at least 5A (substitue a better number if you have one):

R = V/I = 5V/5A = 1 ohm.

Next, P = VI = 5V*5A = 25 Watt.

Not sure where to find a 1ohm 25W resistor...

I've never tested a PS with a dummy load. Perhaps you have an old junker PCB you don't care much about you can use as the test load...
 
Mouser or Digikey has them. You want a ceramic power resistor. A wirewound might work too. If you don't find what you need let me know - I've got some floating about the shop somewhere.
 
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Be careful, that sucker's gonna get pretty hot when you run 5A thru it for a while.

Also, bear in mind that if you're PS voltage goes up to 6 or 7V, it'll be drawing 6 or 7 amps, and the resistor will be dissapating 35 or 50W... well over its rating.

(And don't hook it up to the 12V output...)

I wouldn't let that test run unattended, either.
 
Ahhh, V=IR - the old standby. Thanks for the refresher, I did not think to use that..
And thanks for all the help/suggestions guys, I placed my Mouser order and included a PWM voltage controller just in case U1 is the fault.
BTW, the P/S is rated at 10A max with a +5vdc operating range of 1.6 - 8A. I used the 5A for testing as I just need to poke around on the bench.
I will update this post once I get the rig together.
Thanks again
Jeff
 
Ahhh, V=IR - the old standby. Thanks for the refresher, I did not think to use that..
And thanks for all the help/suggestions guys, I placed my Mouser order and included a PWM voltage controller just in case U1 is the fault.
BTW, the P/S is rated at 10A max with a +5vdc operating range of 1.6 - 8A. I used the 5A for testing as I just need to poke around on the bench.
I will update this post once I get the rig together.
Thanks again
Jeff

And take pictures!!!! :)
 
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