# Low ohmic short 3v3 to gnd



## tjfx96 (Oct 27, 2019)

Hi all,
I am frustratingly trying to locate a 3.3 v supply to gnd short measuring  approx 12 ohms 
on my FV1 Dev board - ive eliminated all components connected to 3.3 supply by buzzing or replacing apart from obviously FV1 and CH341 smt chips - there is no visual sign of issues under high magnification 
However i was wondering if anyone can comment on the properties of say solder blob 
or whisker short  ohmic characteristics and debugging and location,
Thx
T


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## phi1 (Oct 27, 2019)

Just to be clear, when you remove all the components except for the fv1 and ch341 the short (12ohm) persists? If so, it could only possibly be one of those chips failing or some rogue solder somewhere on the pcb?


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## tjfx96 (Oct 27, 2019)

Yes indeed it must those components or rogue solder - as the board has never been powered up my best assumption is it is a solder issue and to my question do you think a 12 ohm short is indicative of a hard to visually locate whisker type solder bridge ie some kind of schottky effect


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## phi1 (Oct 27, 2019)

Not sure. You could try reflowing the pins of the smd chips with a fine-tip iron. Or removing those chips altogether.


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## tjfx96 (Oct 27, 2019)

Yes i was thinking of doing that do you think 375 deg iron temp ok ?
Thx


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## Chuck D. Bones (Oct 29, 2019)

You said the board has never been powered.  I take it you were measuring resistance as a check before applying power.  It might just be that nothing is wrong with the board.  Have you tried changing resistance scales, or using the diode test setting on your DMM?  Also try swapping the leads.


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## tjfx96 (Oct 29, 2019)

Chuck D. Bones said:


> You said the board has never been powered.  I take it you were measuring resistance as a check before applying power.  It might just be that nothing is wrong with the board.  Have you tried changing resistance scales, or using the diode test setting on your DMM?  Also try swapping the leads.



Thx for the reply !
On all DMM resistance scales 3v3 to gnd reads a constant 12 ohms
On the diode test setting it beeps short.

Ive pretty much exhausted all avenues apart from FV1 and CH341 defect.
TBH im close to giving up on this board and unfortunately replacement dev board out of stock (due to FV1 shortage i guess)
Thx
T


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