I'm trying to build one of Rod Elliott's P05 preamp power supplies and have hit a bit of a snag. Using 7815 (+15v) and 7915 (-15v) gives me +14.5v and -17.4v. The first is within tolerance but the second isn't. I've swapped out 7915s and get the same thing. Set up a third 7915 with the test circuit shown in its spec sheet and, again, get the same.
1. Why does my 7915 give ~17.4V instead of 15V?
2. Does it matter for an opamp based pre-amp? Elliott's P88.
1. Why does my 7915 give ~17.4V instead of 15V?
2. Does it matter for an opamp based pre-amp? Elliott's P88.
Are you measuring the outputs with any load? Try a 1K resistor from the -v output to ground and see if it's in spec then
Do have any load on -15 volt regulator?
Connect an led (with correct polarity) in series with 2k7 resistor and connect between +15v and -15V.
Then measure the -15v supply voltage.
Art
Connect an led (with correct polarity) in series with 2k7 resistor and connect between +15v and -15V.
Then measure the -15v supply voltage.
Art
Also watch the pinout. 78xx's are, looking at the front of the chip and reading left to right - Input, Ground, Output. The 79xx series are - Ground, Input, Output.
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