PI-3 short curcuit

[Having a go]

Hi.
First post from a learner.
I have built 2 PI-3's from the excellent ITMD 2nd edition, both are short circuiting.
I could have not loaded the PIC code properly from the PICKIT4, but wouldn't have thought that would have caused a short circuit. I'm trying to check the transistor pins are correct but the book doesn't set this out, nor could I find any thread on the PI-3 on the forum.
I have checked the polarity and components; all seem OK. The boards was made by Oshpark from this sites Gerber files, though they noted no top copper.
Any suggestions how I've stuffed up? John

[Qiaozhi]

Hi.
First post from a learner.
I have built 2 PI-3's from the excellent ITMD 2nd edition, both are short circuiting.

What do you mean by "short circuiting"?

I could have not loaded the PIC code properly from the PICKIT4, but wouldn't have thought that would have caused a short circuit. I'm trying to check the transistor pins are correct but the book doesn't set this out, nor could I find any thread on the PI-3 on the forum.

Please post some photos of the PCB (top and bottom).

I have checked the polarity and components; all seem OK. The boards was made by Oshpark from this sites Gerber files, though they noted no top copper.
Any suggestions how I've stuffed up? John

There is no top copper as it's a single-sided board layout.
Where did you get the Gerber files from? If they came from here -> https://www.geotech1.com/forums/cont...4-gerber-files
then they should be correct. As far as I'm aware, the PCB layout for PI-3 did not change between editions 1 and 2, but Carl should be able to confirm that.

[Carl-NC]

No changes. Look at the flat side, transistor pin-out is E-B-C. If you substituted something other than 3904/3906 then check the data sheet.

Start by removing the speaker and the search coil. Those are the most likely places for a short.

[Having a go]

Hi Quiozhi and Carl
Thank you indeed for your interest and questions.
As I hope the attached photos show, 1 ohm with nothing attached. The pins are EBC from data sheet for the 2N3904 NPN and 2N3906 PNP and GDS for the IRF9630. I can't find the purchase info for the 2N3819 to check.
Any leads welcome for build no.3.
Cheers
John

[Qiaozhi]

See attachment.

[dbanner]

Yes, I think that's a potential short.

[Carl-NC]

Good catch. Looks like my fault on the layout.

[Having a go]

Wow, well spotted
Thanks guys, i'll have a go at cutting it and report back
Cheers
John

[Qiaozhi]

Good catch. Looks like my fault on the layout.

If you examine the Gerber bottom copper, the pad is not actually shorted to the track, but it almost certainly violates the design rules. Due to manufacturing tolerances in the PCB process, this is likely to result in a short-circuit, as appears to have happened here.
I've had this happen before with PCBs, even when the layout has successfully passed DRC.

[waltr]

If you examine the Gerber bottom copper, the pad is not actually shorted to the track, but it almost certainly violates the design rules. Due to manufacturing tolerances in the PCB process, this is likely to result in a short-circuit, as appears to have happened here.
I've had this happen before with PCBs, even when the layout has successfully passed DRC.

Wow, well spotted
Thanks guys, i'll have a go at cutting it and report back
Cheers
John

Since you have extra PCBs, also check those for the short.

[dbanner]

I have built 2 PI-3's from the excellent ITMD 2nd edition, both are short circuiting.

Yep, the other boards ought to be checked.

[bernte_one]

did the PI 3 work?