[Solved] Weird DOUT problem

MIDIbox SID
1

Pin #7 of the Shift Register #4 of a DOUTX4 module is outputting -0.73V (with LED connected) when it should light up.

All the other pins of all the other shift register work correctly (about 2.5V with LED lit)

I already checked LED polarity and resistors…

2

A negative voltage on a module that should only have +5v and GND? Maybe a busted shift register? Have you tried swapping ICs?

3

Since pin7 is next to a GND Pin, it could be a short between those two. Are you sure you measured against GND?

4

Found it, guys. It was the bridge. On mike’s PCBs, there is a bridge for the last pin of the last Shift Register that should be soldered underneath the PCB. It had come off and the SR voltage never reached the resistor. I soldered it again and all is good :slight_smile: Thanks