malfunctioning voltage regulator?

rkc7 · 12th August 2004, 10:33 PM

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

http://ldsg.snippets.org/FILTERS/Pomann/kitsupply.htm

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.

johnnyx · 12th August 2004, 10:44 PM

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.

peranders · 12th August 2004, 10:55 PM

If you are using 79xx, are you aware of that the negative regulator doesn't have the same pinout as the positive 78xx?

moamps · 12th August 2004, 10:59 PM

Quote:

Originally posted by rkc7
Anyway, the +15 lead reads just under 15V, but the -15 reads -19.5V.

Hi,
negative regulator doesn't work properly without any load. Put some resistor (ca 1k) to output and check once again.

Regards
Milan

rkc7 · 12th August 2004, 11:55 PM

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.

12th August 2004, 10:33 PM	#1
rkc7 diyAudio Member Join Date: May 2004 Location: Toledo, OH	malfunctioning voltage regulator? I recently assembled a power supply for my active crossover and I used a design from here: http://ldsg.snippets.org/FILTERS/Pomann/kitsupply.htm 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.

12th August 2004, 10:55 PM	#3
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	If you are using 79xx, are you aware of that the negative regulator doesn't have the same pinout as the positive 78xx? __________________ /Per-Anders (my first name) or P-A as my friends call me

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12th August 2004, 10:44 PM	#2
johnnyx diyAudio Member Join Date: Jan 2004 Location: manchester	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.

12th August 2004, 11:55 PM	#5
rkc7 diyAudio Member Join Date: May 2004 Location: Toledo, OH	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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