#### QCX Schematic question?

Daniel Curtin KF4AV

I am a long time ham with a mathematics background and some electronics, so I am enjoying building and studying the QCX. My question is that I don't see explicitly on the schematic that pin 8 of several of the ICs is connected to 12V (really 11.67 with the diode installed.) I know that pin 8 is Vcc. Does that generally go without annotation in schematics, or am I missing something. My eyes aren't what they used to be!

Gregg Myers

Hi Daniel,

I think you are looking for this notation in the schematic. It is in the upper right corner of the schematic page. But yes, it does not specifically tell you which IC's but you see pins 8 attached to 12 volt and pins 4 attached to ground. There are 6 pairs, representing the OP amps in the circuit.

73,
Gregg W7GRM

On Tue, Jun 16, 2020 at 8:03 PM Daniel Curtin KF4AV <danieljcurtin42@...> wrote:
I am a long time ham with a mathematics background and some electronics, so I am enjoying building and studying the QCX. My question is that I don't see explicitly on the schematic that pin 8 of several of the ICs is connected to 12V (really 11.67 with the diode installed.) I know that pin 8 is Vcc. Does that generally go without annotation in schematics, or am I missing something. My eyes aren't what they used to be!

Daniel Curtin KF4AV

Thanks. I knew it had to be somewhere!

Simon Kennedy

Thanks for asking that Daniel. It is a question that I have often wondered.

On Wed, 17 Jun 2020, 03:28 Daniel Curtin KF4AV, <danieljcurtin42@...> wrote:
Thanks. I knew it had to be somewhere!

Andrew Lenton

Hi as the all or most ICs’  have the same rail and earth pins 8 and 4 why draw a power rail line to every pin 8? And  an earth, or ground line to pin 4? It makes the diagram easier to follow, imagine you had 100 IC’s on a board, you would have 200 extra wires on the diagram! Some simulation programmes allow you not to bother connecting power and ground.

BR

Andrew G8UUG

Jim W7EED

Every schematic capture program that I've used requires the power and ground pins be connected or they will complain about missing nets. Plus, the PCB layout software requires these connections, also.  Be careful about generalizations like "as the all or most ICs’ have the same rail and earth pins 8 and 4 ..." because that's definitely not true.  Even though It's true that simple op amps have generally established a pin out standard, even this doesn't matter.  Many op amp circuits connect a negative voltage to the "earth" pin and there is no ground connected to the op amp at all.  This allows improved common mode voltage input range and wider output swings.
--
73,
Jim W7EED