I just ordered 10 of the RS232 shields from Mouser to replenish our stock. We were using the DFRobot shields, but looking at the schematic for these, I thought it was worth a few dollars extra to have the protection Zener Diodes D4 and D5 on the RS232 Rx/Tx lines (some of the DF shields had gone bad and they do not have any protection diodes).
However, unlike the schematic, there are only solder pads where Zeners D4 and D5 would go. There was no mention of these parts being missing. Did I get a bad batch, or does the schematic need to be corrected?
Can I send these back for repair or can you send me a batch of SM Zener diodes to solder on?
Did you test the new shields? Are the functional?
Hi there,
So , If there’s a schematic viewer on the wiki page for the product in question, you can see if they are Marked “DNP” (Do Not Populate) often that will be that case and it’s an Option. or the IC may already contain them. YMMV
Seedineers can respond. and/or perhaps they can be added.
HTH
GL 
PJ 