Someone Let the Electric Pixies Out

Today, while in the lab, managed to do some damage to my jumperless and was hoping someone may have some thoughts as what i should look at reworking first:

Failure mode is the following:
Position 25 of the jumper board is stuck at -5.29vdc when referenced to the GND rail. The remaining design appears to be functioning normal.

My first thought is that CH446Q “D” has been damaged.


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Interesting, yeah that does look very much like Chip D is blown.

Are you getting negative voltages on any of rows 23-29?

And it being not all the way to ~-9V means it’s also probably shorted to GND through a the crosspoint switch.

Do you have a hot air station? If so, try measuring the ±9V supply (you can just flip the rail supply switch to ±8V and it’ll be a diode drop above that), then removing chip D and measuring again.

If it reads higher with it removed, that’s a pretty good indicator of that being the issue.

Either way, I’ll ship you out a new Jumperless tomorrow with some extra CH446Qs so you can hopefully fix that one and have 2 of them.

Thanks for your reply!

rows 23-29 seem to be functioning as intended with the exception of row25.

I do have a hot air station and removed chip ‘D’. after removal it appears the row is floating no longer reading -5.29VDC

prior to removing Chip D, with the rail supply switch set to +/-8V, i get -7.72V and +8.24V referenced to the GND rail. After removal of Chip D i get the same values.

All the folks here at the office appreciate your assistance let me know what else i may do to further the troubleshooting process.

Cool, I guess it wasn’t pulling on the power supplies, because those are voltages are right where they should be.

The replacement 1 and a half Jumperlesses will get there Saturday. The half one is for spare parts you can transfer to the one you have.

But in the meantime, if you’d like to look into what caused the issue in the first place here’s some stuff you can check.

First, what was happening when the electric pixies escaped? If it was something that obviously would put a lot of stress on a CMOS switch then you probably don’t need to bother checking this, but you can if you want.

One problem that a couple of people experienced was the internal pulldowns not working on the RP2040 so the DATA, CS_, or CLK lines were acting like they had a capacitor on them and not sending proper signals. Check out this forum post about that and which lines to check with an oscilloscope.

Also, update your firmware and JumperlessWokwiBridge app to the latest versions. Some routing bugs in the older firmware could possibly cause mayhem. And the new bridge app should automatically keep your firmware up to date.

I’ll send you a DM with your tracking number for the replacement.