On Thu, 3 Feb 2005, Ake Hedman wrote:

> I have two identical boards on my desk  and have some noise problems with one 
> of them. Both have a sensor input and a cable of about two meters attached to 
> the input plus are connected to a CAN bus. The sensors are decouples on the 
> board with a 0.1uF cap. Above my bench I have a fluorescent lamp and one of 
> the boards get very upset (watchdog reset) when this lamp is turned on/off.
>
> First it is strange that only one board does this but my question is how do 
> one approach a problem like this?
> I have also tested a piezo gas lightning device close to the boards but it 
> does not disturb the systems.

Are the boards new (never worked) ? Imho you are looking for a cold 
solder joint or cracked part (cap, resistor), likely in the grounds or 
decoupling areas. If you have a fox (from a fox&hound set) you can try 
injecting signal into the ground at various chips and see if it is 
sensitive.

Peter
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