Testing: U5 (78L10) getting very hot

[neilbaldwin]

Just finished building the euro version (with the daughter board) and have been testing/calibrating.

All good so far but I've just flipped over the module to start the trimmer adjustment/calibration and noticed that U5 is very hot. I guess it's the nature of it's job but is it normal to get so warm?

Thanks,

Neil

[neilbaldwin]

Actually, just checked the voltage, +12V in but 0V out so I guess it's fried?

[elmegil]

It could also be a short to ground on the 5V rail. Power off and check continuity. Possibly without the 7805 in place, in case IT is the short.

[neilbaldwin]

Thanks for the reply.

Doesn't seem to be a short. I've checked the gate output and that's coming out at 10V and there's no continuity between the GND and output of any of the output sockets.

Or am I barking up the wrong tree there?

[blue hell]

Could be its not a hard short .. when the regulator gets hot it will shut down too.

[elmegil]

[neilbaldwin]

Hang on, there are no 7805s on the build are there?



Edit: well, there appears to be continuity between the input pin of the 78L10 and the Vcc pin of the CD4066s. That's not right is it? I thought the Vcc to the 4066 should come from the output of the 78L10?

[elmegil]

[neilbaldwin]

Got it!

Oh man, there was a microscopic bridge between the output and ground pads of U5 but on the component side of the board so I had to remove it to find it!

Thanks all for the input and help.

Onwards with the calibration!