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Old 05 November 2019, 18:47   #1
chue
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A500 Power Supply 5V rail short?

I am in the process of recapping my A500 power supply. The new caps are in place, but I thought before powering it back up that I would check for shorts.

I am measuring a possible short (45 ohms) between the output 5V pin and ground. This measurement is between pins 1 and 2 on the attached image. Is this indeed a short?

I have looked at the caps and the board and don't see any obvious shorts, but thought I would ask here before investigating further.
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Old 05 November 2019, 20:33   #2
robinsonb5
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Are you sure you're not just measuring the resistance across a shiny new (and presumably fully-discharged) capacitor that your multimeter is desperately trying to charge?
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Old 05 November 2019, 20:45   #3
chue
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Quote:
Originally Posted by robinsonb5 View Post
Are you sure you're not just measuring the resistance across a shiny new (and presumably fully-discharged) capacitor that your multimeter is desperately trying to charge?
That's entirely possible, I just wanted to get some thoughts here before I power it up and possibly let out the black smoke
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Old 05 November 2019, 23:32   #4
chue
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I guess I was just being cautious. After looking at it again for shorts and not finding any, I plugged it in and it worked. Problem solved!
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Old 06 November 2019, 00:00   #5
Daedalus
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Nope, 45 ohms is pretty normal for a setup like this, with things like capacitors charging, pull up / pull down resistors and semiconductor leak currents all adding up. After all, 5V into 45 ohms is only a little over 100mA, whereas a fully powered-up Amiga 500 consumes more than ten times that amount. So I wouldn't worry about that.
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Old 06 November 2019, 00:05   #6
chue
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Thank you for the confirmation and explanation, @Daedalus.
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