Is my 3DR pixhawk 1 bad?

I have an original 3DR pix running the latest version of plane. I had a fire [ lipo went into road flare mode! ] in my plane. I thought the pix survived. I’ve since downloaded the latest stable vs of plane and installed. Connected it to mission planner and all seems fine. However… as I am redoing all my power supply set up I noticed that if I power up just the servo rail the pix only 1/2 fires up? I see three LED’s light up but the rest doesn’t… the main LED… telem radio… etc don’t get power. Previously the servo rail would act as a back up and power the entire pix. Is it defective? is there a param I don’t know about? I have an identical original 3DR pix 1 and I tested it the same way just powering up the servo rail and it powers up the entire board as expected. It has an older version of copter on it. I’m thinking my other pix 1 was damaged somehow and I’m only now seeing it. Thoughts?? Thank you

so if your first fc is damaged as i read in your description i suggest you don’t fly anymore with that… better change it.
if you need provide a power redundancy to the servo rail on your fc don’t provide more that 5.32v…in ubec Vout, just solder a cap and a Zener diode… cap will reduce spikes and with the combination of the Zener diode it will work as a power regulator.

Yea that’s what I was setting up when I noticed the problem.