WTF happend with my unity? (overvoltage error)

You should always measure resistance AFTER removing the resistor, the rest of the circuit will interfere with the measurement.

Unless you have a second unity to compare a point by point measurement, in circuit measurement are “sometimes useless…”

If you had an impact you probably have a cracked solder joint, or a cracked via, so there is some current going through… microscope or macro shots would help try to find this…

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3mohm? megaohms? How are you getting a higher resistance reading from a resistor when it’s mounted? If the resistor is 39k then you cannot get a reading higher than 39k no matter what the resistor is attached to…

Resistance in parallel can only drop, his measurements makes no sense.

Yea sorry hard as hell to get a good contact redone the measurements now the resistor is 39k unconnected and here is a video on how it behaves connected just to make it easier

Still says overvoltage.

Have a hard time to think a cracked solder could be the issue then it should show up as 0 volts or lower cause of bad contact or am I wrong?

Is there any way to get over this in the fw?

Sure, still not good practice to measure in circuit, if you have solder cracks, or tracks broken by applying force on the resistor with your probes you can be momentarily making the problem worse or better…

I’m not sure, I still think you should try to find the hardware issue…

Agree with both. The hardware issue may get worse if not resolved. Better to diagnose it properly and have it repaired. Your safety is at risk. If the drv blows and the board loses power you could be in for a tumble.

Yes you are both definitely correct! Will send beer money for the one that can help me get to the bottom of this. Superstoked to get out riding the board. Just got done with it after a few months waiting for parts and this happens on my third ride.

Signed up for the neoboxes just in case otherwise I got another build in mind for them.

If you can’t figure it out, I would say send them to @JohnnyMeduse He does DRV replacements and all that. I got a Unity on the way to him for blown antispark fets.

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Thanks for the tip its my last resort I want to see if there is anything more I can do myself it’s just really hard without any documentation.

Shipping from sweden is idiotic expensive 50euro to send a small box insured to a eu country and you can’t even send insured outside of EU so might not be worth sending considering labor and taxes (If its outside EU) when you get it back. we will see :slight_smile:

Oh, if you’re in the EU there’s a guy there that does the same thing. Forgot who it was maybe someone else can chime in.

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@seaborder maybe?

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^ yes that guy.

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@Deodand you dont have any more leads on what to check? :slight_smile: Would be great if there was schematics on the whole voltage measuring part. I messed up the solder on R23 one time and then it showed 0 volts so at least there is signs of life

Those two resistors are the entirety of the voltage measurement, you could also check pin 15 on the MCU, highlighted the trace in red here:

But reworking that takes a bit of finesse. you could try gently applying a bit of pressure to these pins with a piece of rubber while its on and see if it effects the voltage reading. But yes its those two resistors then into an analog pin.

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Thanks much appreciated! Will see what i can do.

@Deodand Still the same :confused: Reflowed pin 15 and removed the resistors so I could measure between the pads then put them back.

Here is a diagram I did when measuring with the resistors removed. I hope you understand it. It’s just like its mounted on the picture.

There really isn’t anything more that could be wrong on the way to the MCU. Could the MCU have taken a shit? If I was to change it can I just get a new one then upload the bootloader then fw or will there be something missing?

Also have a theory that something is wrong in the memory that a fw update wont fix cause its not touching those parts of the code. I really have no idea how the software works here so just a wild idea and you probably know the answer :slight_smile:

Could you check if the 3.3V and the 5V are good?

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We are getting somewhere!!!
5v on the comm is just at 2.5v and the 3.3v is at 2.4v when measuring to the servo GND

So does the MCU use a voltage reference? Cause that crossed my mind when looking at the datasheet

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the MCU use the Vin as reference.

Cold you check if 3.3V is shorted with the 5V

Hmm its a bit unstable but evens out at 14k

So the 5V and 3.3V are not shorted. But there is something wrong with the 5V.

Could you post some picture of the PCB? Also have you try without the bluetooth?

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