Mislabelled Regulators

[R.Fahl]

Just built another power supply to test some new modules.  Measured the
output voltages: positive supply 15.11 volts DC Negative -18.3 vDC.  Didn't
make sense to me, so I ended up swapping regulators.  Same result.  This
made me suspicious.  Replaced the negative regulator again, but this time
from a different manufacturer.  This time the negative rail was -15 volts
(close enuff).  Looks like someone sold me a batch of mislabelled 7918s.  I
take it someone in Malaysia was feeling underpaid.