BSD ground short issues HELP!!!

[Ragnar1057]

R26 could be relevant. If it was faulty, it might prevent pin 6 of the comparator (LM339) from being pulled low. This would cause the positive input of the comparator to be lower than the the negative input. The output of the comparator would then be low which would make the CPU board believe that the switch is closed.

 

[newdos]

OK so what I have done to rove loom is ok i disconnected the opto from the coffin popper and the error goes away. is that what you mean?
D11 replaced no and no change.

Just checked R27 2k spot on and R26(diagram says R6 which is wrong!) and it appears to be open circuit!!! yet not a mark on it very odd. I will change it and come back

Cheers

Kev

Sure enough it was R26 open circuit. I have never seen a resistor go open circuit before with out being black or disintegrated!!! guess it was just tired or caused by the heat from the big resistors near it which do run hot.

Big shout out to everyone for all their help on this. never could of done this with out your help. The power of the forum!

Cheers

Kev

 

[newdos]

And here is the proof!!! not a mark on the resistor!

 

[AlanJ]

Yey !!!! Do I get a prize

 

[Calimori]

Awesome work, glad we got there as a collective. It does show there are different ways to work through the issues and narrow it down.

 

[Ragnar1057]

@AlanJ - good call on those resistors