Welcome! Log In Create A New Profile


trying to repair sanguinololu need help

Posted by fahraynk 
trying to repair sanguinololu need help
February 23, 2013 02:28PM
I took out the 7805 - > ic1 because i thought i might have fried it. The board powers on when there is usb but not when there is only 12 volts from screw terminals.

I then plugged in the board and did some tests...

1) from the 5v out pin and the ground pin im getting 0.5V (by pin, i mean pin slot, as in where the 7805 would actually go into the board, im just going to call it pin.)

This is my first question... shouldn't it be 0 volts when the regulator is not in the board ? where is the 0.5 coming from?

2) from the V in pin to the ground pin im getting like... a degrading voltage that starts at something like 4 volts and decreases. I was expecting 12 volts here... but from the v in pin to the ground at the screw terminal it IS 12 volts. It should be the same between the vin pin and the ground pin right ? I tested continuity and it beeped when i put my tester from the ground pin to the ground screw, so I dont see why the voltage reading would be different from vin pin to ground pin, and vin pin and ground screw terminal ! actually, its the SAME degrading voltage level from vin pin to ground pin and v in pin to the v out pin...

Can someone shed light on this ? thats my second question.

3) from the Vinput pin to the + 12 screw terminal, im getting 7.2 volts... shouldn't it be 0 ??????

my hope is that if i change the 2 capacitors and the voltage regulator that the circuit would work, but these readings are making me confused.

yeah... I accidently put the board ontop of shavings of coppor on my work bench, which shorted it when i powered it on... I dont see any burn marks or anything. I thought it was the regulator because when I originally tested the voltage expecting +5 coming out I only saw something like 0.5 or around there.

please help

Edited 1 time(s). Last edit at 02/23/2013 02:31PM by fahraynk.
Re: trying to repair sanguinololu need help
February 23, 2013 06:12PM
1) The 0.5V probably comes from having the USB powered. The FTDI chip will be trying to put logic 1 on the RX pin of the ATMEL. That will feed onto the 5V rail through the ESD protection diodes in the ATMEL.

2) Not sure, seems like the ground track is broken despite your continuity tester.

3) Seems like the track from +12V to the regulator is broken.

Most likely the copper shavings shorted the 12V rail and the current from the PSU burnt the tracks away. Not sure why that isn't visible though. Possibly some vias have gone.

Re: trying to repair sanguinololu need help
February 25, 2013 02:05PM
wasnt testing with the usb actually plugged in

Thanks so much for your response !

what do you mean vias?

If I run a cable to the regulator VIN pin, and disconnect the pin from its track... that might help right? and if that fixes it I could create a new track. Same for the ground if its really broken.


I would try this... but thats the thing, in my original post question number 1, it says that im getting small .5 voltage readings between the ground pin and the VOUT pin of where the regulator is supposed to be. That and the fact that im getting the weird degrading voltage between the VIN pin and Ground pin and VOUT pin and ground pin, which I suspected was weird capactiance behavior...

Repair theory - Disconect everything regulator related, connect a new 7805 with test wire directly from screw terminals for ground/+12/Vout to caps ect.

Unless you guys think im going to have to replace the capacitors as well? or something else?

ps: anyone know if theres a picture of the copper tracks from point a to point b on the sanguino somewhere? Im having a hardddd time just using my eyes between point a-point b to see them.

Edited 1 time(s). Last edit at 02/25/2013 02:16PM by fahraynk.
Re: trying to repair sanguinololu need help
February 25, 2013 03:21PM
Are you saying you get 0.5V with no power on the board? That would be odd. Perhaps a charged cap somewhere but I would expect it to decay.

If you get a decaying voltage measure from 12V to ground then there are two possibilities. You have a capacitor in series with the meter, so either ground or +12V is not connected. Or you have a capacitor charged via a very high resistance and when you put your meter across it it discharges. either way, what you think is 12V and ground, at least one of them isn't.

There are pictures of the tracks here: [reprap.org]

Vias are the copper plating through holes that connect one side of the board to the other. When you removed the regulator you may have broken it.

Sorry, only registered users may post in this forum.

Click here to login