If It were drawing excessive current, it would be getting very, very hot to the touch.
Make sure the 74AC00 is installed in the correct direction.
Soldering issues are by far the most common reason a kit does not function. Rarely is it a bad part, in fact it’s almost unheard of. You have to work really, really hard to damage a modern IC. Reverse supply polarity will kill a lot of ICs’ but not always. They usually survive being in the wrong way around.
I sure hope you don’t have to change out IC4, that will not be easy.
73, Steve KD1JV
>and it appears that IC4 is drawing excess current. Static
> measurement shows ~140 ohms VCC to ground. Everything else checks OK on
> the 5V bus.
Before replacing anything be completely sure.
Most faults are solder whiskers, if it was like it from the start even
an unetched piece of copper, component failure is unusual except when
A test is to gently lift pin 16 with a pin.
73 Alan G4ZFQ