PCB will not power up, what is this part?

Thread Starter


Joined Jul 23, 2008
Hello, I have a PCB from X-rite spectrophotometer.
Last time I turned it off it worked fine, now it will not turn on.

PSU is 12V brick type, it is OK.
The PCB has led that indicates it ON state, it does not light up.
The real mechanical switch oh PCB switches ground rail??? WTF

I had a wall switch to turn the spectrometer that is wired on APC UPS, so no power loss etc.
The only thing I can think about is shock from PSU turning on because the (real mechanical switch) turns on/off negative rail not positive.

What is the part the first on power rail?