"Jasen Betts" schrieb im Newsbeitrag
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On 2008-12-02, Brian Gregory [UK] wrote:
"geoff" wrote in message
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geronimo wrote:
Hello all, it was just a bad batch of 7805s!
Possibly a 'fake' device.

I've a vague idea that I remember a 7905 accidentally fitted instead of a
7805 did something very similar in something I was working on.

hmm, yeah, given a 12V supply and no load you'd get that.



Looks like operating the 7805 as pulse with modulator / switching regulator.
Some digital voltmeters show unreal values, when the DC inputs are driven by
pulses. Oscillation usually happens, when the input and output capacitors
are missed.
Place at least 1µF/16Volts electrolytic cap's from input terminal to GND
Pin and also from output terminal to GND Pin. Place the capacitors as close
as possible to regulators case. Please report the voltage reading.
w-ro