I had some pcb's made by advanced circuits using the latest version of Eagle. I had mocked up and proven out on a breadboard my circuit of which I will not post here, So I know my circuit is functional. After I built the circuit on the pcb and powered it up I noticed that the 5v reg was hot and disconnected power and probed my circuit with my meter as well as visual under a scope for shorts but I can not find any. I have bad continuity across my .1uf caps for decoupling and have removed 2 of 4 of them starting from closest to the v reg. I probe the pads on the cap I just removed and still have bad continuity. I think I have a short to ground but can not find it and dont know what else to do. A fresh board with no components meters fine. All of my parts have been derated. This is a double sided board. Any suggestions on troubleshooting would be appreciated.

Val.

 

Define is bad continuity. Power the board and measure regulator voltages.

Does board function?

 

Don't always presume a circuit that works on a breadboard will work on a printed circuit board especially so when moderate to high frequencies are involved.

Breadboard > Prototype PCB > Final PCB is the way to go?

You'll need to post your schematic and PCB layout if you're going to get any help.

 

Did you pay for electrical test on the PCB? That will rule out any net to net shorts..
But as you stated the "short" isn't present on a new unpopulated board so that rules the board out..
So we are done here until you can provide more detailed information..

Its NEVER easy to diagnose problems with someone elses circuit without any real information over the internet..

 

I had some pcb's made by advanced circuits using the latest version of Eagle. I had mocked up and proven out on a breadboard my circuit of which I will not post here, So I know my circuit is functional. After I built the circuit on the pcb and powered it up I noticed that the 5v reg was hot and disconnected power and probed my circuit with my meter as well as visual under a scope for shorts but I can not find any. I have bad continuity across my .1uf caps for decoupling and have removed 2 of 4 of them starting from closest to the v reg. I probe the pads on the cap I just removed and still have bad continuity. I think I have a short to ground but can not find it and dont know what else to do. A fresh board with no components meters fine. All of my parts have been derated. This is a double sided board. Any suggestions on troubleshooting would be appreciated.

Val.

I'm going to guess bad continuity is a short??
If the empty board is not shorted I would visually inspect the 5 volt line for any bridges that might go to ground.
If that doesn't work you could start to populate your spare board with parts starting with the regulator and measuring as you add sections. This may be difficult depending on your boards circuits.
Edit:
Schematic.....

 

Is the Vreg heatsink tied to ground or the caps could be bad ???

 

Using one of the bare boards as a guide, I'd follow the 5 volt power net and look for shorts to ground, or bad soldering. If I couldn't find anything on the loaded board, I'd start removing components powered by 5V one at a time.

 

Devices like these

work. I bought something many years ago called ShortSqueek.
But essentially a tone milliohmeter.

Without full electrical testing, you have no idea if it's the board or a component.

 

I had some pcb's made by advanced circuits using the latest version of Eagle. I had mocked up and proven out on a breadboard my circuit of which I will not post here, So I know my circuit is functional. After I built the circuit on the pcb and powered it up I noticed that the 5v reg was hot and disconnected power and probed my circuit with my meter as well as visual under a scope for shorts but I can not find any. I have bad continuity across my .1uf caps for decoupling and have removed 2 of 4 of them starting from closest to the v reg. I probe the pads on the cap I just removed and still have bad continuity. I think I have a short to ground but can not find it and dont know what else to do. A fresh board with no components meters fine. All of my parts have been derated. This is a double sided board. Any suggestions on troubleshooting would be appreciated.

Val.

Can you bring the board up a small circuit at a time? Populate only the power section and see if that comes up, then add other circuits one at a time.

 

Try the smoke test: power the board up, and the component that is bad will emit smoke, or at least get warm which you can detect with your finger.

Finding shorts with an ohmmeter is difficult as there is very little difference in resistance across the power lines, but a very accurate 4 point probe meter may work. Or... make do with any source of current and use your voltmeter (usually more accurate than a common ohmmeter) and find the lowest voltage hence the lowest resistance hence the shortest short and the problem.