24 Aug
2014
24 Aug
'14
10:58 a.m.
----- Original Message -----
Date: Sun, 24 Aug 2014 10:48:46 -0500
From: "drlegendre ." <drlegendre at gmail.com>
Now back to your original point, the one you felt I was missing..
Pin #41 had the 470 to gnd, but no 330 to VT+, so it
was at a true logic
low, pulled down by the 470. This causes the 7404 output to go
high,
turning off the LED. When I connected the 330 part, Pin 41 came up to
2.8VDC (about 1/2 of VT+) which I guess the 7404 sees as a high (?)
switching off the 7404 output and turning on the LED.
All good so far?
-----Reply:
Just like your misleading post about the LM309's output being connected to
the 8V supply rail, you had specifically said that "there aren't *any*
resistors connected to it, which is why it's sitting low. I checked that
out." No mention of the 470 ohm pull-down resistor...
Maybe you could save some time by checking more carefully before posting...