Did I fry my PCB?

I was putting my pcb v2 (cytron/nano) in tractor and very foolishly connected Battery v12 incorrectly. After turning on I heard a click (probably the relay) and then slight burnt smell. I see no obvious burns on pcb but now I can’t power up cytron and don’t know where to start troubleshooting. Don’t have a ton of spare parts either .

Any thoughts on parts to replace? Any help would be great !

Haha ! I’ve done same stupid thing a few months ago , check this Tips and tricks on how to assemble PCB v2 - #31 by Tooki57 . If you are lucky , just repair the track with a wire .

Thanks for the tip! What did you end up doing to fix? I tried going from onoff switch to d3 but keep having same issue.

I wonder if it is something to do with power in? Where are you drawing your power from? I am taking from tractor battery but am wondering if this is too much power for the board or something. I keep blowing fuses.

I have just the lines between on/off and d3 , but i justed reverse polarity of power .
check every connection , the polarity of diodes, condensators and voltage regulators , then check ,and re check , there s probably an error somewhere …I use a direct wire from battery. If everythings good , a 15A fuse should be enough .

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If you use cytron md13s it might be burnt as it is not protected against wrong polarity, so take wires off the cytron and try again, if everything else is correct.

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Hi everyone! i started with my pcb v2 and the same problem happened to me. Wrong polarity. Could anyone send me a picture of how to fix this ? i think the relay burnt. Should i work without on/off switch/relay ?
I don’t see any picture in this subject. Is it too old?
Thanks !

Yes too old.

But check if your cupper line between D3 and on/off connector is burnt, that was what pictures shows.
Replace with a wire and voila pcb works again.
Off course with correct polarity :wink:
Relay is not harmed by wrong polarity.

Thanks for the answer. I checked the lines and found no one burnt. Is it possible that if i connect the arduino directly to the fz-g1 tablet and at the same time put the pcb on 12V the fuse on 12V blows ? :thinking: should i have only to connect to the usb hub ?
I’ll try again step by step connecting things one to one
Or perhaps is d3 diod dead ? but the line is ok!

You must send pictures of the whole pcb, so we can help to check the components and their orientation.