I'm troubleshooting the 6 volt side of a power supply for a BPM tube
mic. I have one failed (shorted) diode left to replace which goes to
ground, in parallel with a filter cap and .002 cermic cap. It comes
between the rectifier output and pin one of the voltage regulator
(7806). I assume the power supply should work without this diode there
at all, and I can't figure out why it's there. The rest looks pretty
much like a textbook power supply cicuit. Can anyone explain what the
purpose of this diode might be and what might be a replacement?