what ground do you use when nothing says GROUND?

vintagegamer

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I need to check continuity on some things on my Time Warp pin, and unlike the boards you see in Atari that have rings which read GROUND, I have no clue what to use as the ground for things like connectors where a wire is not assigned specifically as a ground.

At the bottom of the headbox on this pin, there is a ground strap that is held down by a wing nut. Is that a sufficient place for me to put the black lead when checking continuity of wires on the CPU-MPU? What is the general rule of thumb for this?
 
Why do you need a ground for checking continuity? Continuity is a check from one end of a wire to another, no ground is needed. Ground is something used as a reference point when verifying differences in potential (voltage levels). The only time I ever use a ground when verifying continuity is when I am working on a cable that exceeds the length of my meter's leads when working on the submarines.


The ground strap you mentioned, or any of the screws that hold the circuit boards as well as the brackets that hold the boards should be a good ground.
 
Why do you need a ground for checking continuity? Continuity is a check from one end of a wire to another, no ground is needed. Ground is something used as a reference point when verifying differences in potential (voltage levels). The only time I ever use a ground when verifying continuity is when I am working on a cable that exceeds the length of my meter's leads when working on the submarines.


The ground strap you mentioned, or any of the screws that hold the circuit boards as well as the brackets that hold the boards should be a good ground.

I guess I've got things mixed up in my head then. I feel like an idiot posting this but just to make sure I'm getting this right, I put the red lead on one end of the wire, put the black lead on the other end of the same wire, and if it reads a value then that wire has continuity? I guess I'm making this harder than it is. Sorry for my stupid questions :(
 
Yes, that is a continuity test. Make sure the meter is measuring resistance or ohms. Preferrably you should have a reading close to zero, and if your meter has an audible beep thta will speed things up.

Another thing I like to do when measuring for continuity is check for crossed circuits. move one lead or the other to other circuits that shoould not be connected and see if you get continuity. Just remember all grounds should show continuity to one another so you only want to do these cross checks from the source side of a circuit.
 
So now in regard to if I want to check the voltage of a pin on a connector coming off of a board, I would put the red lead on the pin in question, what would I use as the place for the black lead (provided there's no wire specifically labeled 'ground' or anything on the actual board labeled 'ground')? For that I can use the wire under the wing nut or the other locations you mentioned?
 
Preferrably you will use a ground on the board. Virtually all screws holding the boards in place are attached through the ground plane of the boards. I just attach to a screw with an alligator clip and then move the red lead around looking at power.
 
Preferrably you will use a ground on the board. Virtually all screws holding the boards in place are attached through the ground plane of the boards. I just attach to a screw with an alligator clip and then move the red lead around looking at power.

Excellent tips, thank you very much. Hopefully this thread helps some other folks as well.
 
Preferrably you will use a ground on the board. Virtually all screws holding the boards in place are attached through the ground plane of the boards. I just attach to a screw with an alligator clip and then move the red lead around looking at power.
Another trick is to clip onto the ground side of an electrolytic capacitor. It's easy to spot and there's always plenty of space to clip onto the metal lead.
 
Another trick is to clip onto the ground side of an electrolytic capacitor. It's easy to spot and there's always plenty of space to clip onto the metal lead.


If you are talking about axial capacitors I agree with you to a point.

You should make sure that the ground of the cap is actually the ground of the system in question. There are times when an axial is using a lower voltage source as the ground. Any place where a negative voltage value is present can have some axials backwards...
 
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