Electro Tech forum,
I have a 555 timer circuit built up on a Radio Shack bread board.
It's running in astable mode putting out a square wave that is
high for .5 sec and low for .5 sec and driving a couple of leds.
It works fine with a 9 volt battery and a LM317T voltage regulator.
Recently I replaced the battery and regulator with a 110 to
9 volt transformer(actually puts out about 10vac), a BR805D/TP2
full wave bridge and a 7805T 5 volt regulator with a 220uf
capacitors on the input and output.
This also works fine, until I plug in an SN74HC14 device anywhere
else on the board and power it up. Then the output of the 555
increases about 20% in frequency. Plugging in other types of ic's
like 7447, 7490 ect. don't cause this problem.
There is a .1uf bypass cap on the 7414 from power to ground and
the 5 volt supply doesn't appear to have any glitches on it.
Am I doing something wrong or is there something I don't know
about a 7414?
Thanks for any reply,
Jerryd