JJFORTY
Member level 1
Hi All,
I have this faulty board which does not want to operate unless I touch one of the nodes with finger or DMM probe tip. I have many of this boards 100% operating so it is not down to design error. I have measured all component values and all Ok. I have also replaced all Ic's and C392 which looks to be right in the path of the problem but to no bail.
I have taking all measurements and compared with working board..
Red: Working units
Blue: Faulty units
Black: When node is touched
When node is touched pin 7 Comparator (U315-B) input increases about 10mV and this makes o/p to rise to 3.3V so board works.. I have done this test to a working board and input pin 7 also increases about 15mv ... so what is making the faulty board operate when node is touched???
I appreciate any input..
Thanks
I have this faulty board which does not want to operate unless I touch one of the nodes with finger or DMM probe tip. I have many of this boards 100% operating so it is not down to design error. I have measured all component values and all Ok. I have also replaced all Ic's and C392 which looks to be right in the path of the problem but to no bail.
I have taking all measurements and compared with working board..
Red: Working units
Blue: Faulty units
Black: When node is touched
When node is touched pin 7 Comparator (U315-B) input increases about 10mV and this makes o/p to rise to 3.3V so board works.. I have done this test to a working board and input pin 7 also increases about 15mv ... so what is making the faulty board operate when node is touched???
I appreciate any input..
Thanks