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Old 12th August 2004, 10:33 PM   #1
rkc7 is offline rkc7  United States
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Default malfunctioning voltage regulator?

I recently assembled a power supply for my active crossover and I used a design from here:

Anyway, the +15 lead reads just under 15V, but the -15 reads -19.5V. I checked over everything, and it seems correct, could this be due to a faulty voltage regulator? The regulators are 7815 and 7915. Thanks.
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Old 12th August 2004, 10:44 PM   #2
johnnyx is offline johnnyx  United Kingdom
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I would check for a short between the IN and OUT on the 7915. I've had that a few times. The pinout of the 7815 & 7915 are different; if you didn't use the PCB, check that from the data sheets. If there is a reverse - biased diode between IN & OUT , check it's the right way round.

Hope this helps.
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Old 12th August 2004, 10:55 PM   #3
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If you are using 79xx, are you aware of that the negative regulator doesn't have the same pinout as the positive 78xx?
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Old 12th August 2004, 10:59 PM   #4
moamps is offline moamps  Croatia
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Default Re: malfunctioning voltage regulator?

Originally posted by rkc7
Anyway, the +15 lead reads just under 15V, but the -15 reads -19.5V.
negative regulator doesn't work properly without any load. Put some resistor (ca 1k) to output and check once again.

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Old 12th August 2004, 11:55 PM   #5
rkc7 is offline rkc7  United States
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Thanks Moamps, I guess it was fine, just needed a load. It's measuring correctly now. And yes, I knew the pin configuration was different, and everything was correct on the board, that's why I was confused. Thanks to all.
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