No LED 2

[bendala]

I have just finished my third LE and when i run the tests I get no response from LED 2. I have ruled out the 485's as I have swapped them onto a working board and it functioned fine. Also I have re flashed the PIC twice to no avail. Any other things I should look for? Any Help would be greatly appreciated Thank you in advance!

[Jeffl]

LED or opto in backwards?

[rm357]

+1

Also make sure pin 3 on the pic is properly seated and not bent under.

Might try swapping optos with a known good channel.

[bendala]

Thank you for the quick response I didn't even think of the problem lying with the opto's I switched it out for a spare I had and it works fine. Another problem arose and it is now the Data Link light is lit with nothing attached. Any Ideas.

[bendala]

  Alright fixed the problem by swaping the 485's does anyone know why this happens sometimes?

[Jeffl]

Of the many, many, many LE's I have built I have had a number of RS485 chips that did just that.  I would swap #1 for #2 and both would work.  I wouldn't rule out the  chip is bad based on one swap.  Sometimes I wonder if it's just the connection.  The chip holders are nice for this reason but I think most times its the chip holder instead of the chips themselves.

[bendala]

I went through and reflowed all of my joints on the board just to make sure that a bad joint was not adding to the issue. Thank you for all of your replies. The show is up and running!