PMU Reset Drobo 5D


My Drobo 5D is not booting correctly. It becomes stuck after a few seconds and remains with an yellow/orange power light. The lights for the hdd slots have the same color.
In order to get more information I red out the serial port. The boot process ends up with the message:

#The PMU has been reprogrammed! … Waiting for the inevitable Reset”

Does anyone know how to reset the PMU of the Drobo 5D by using the serial connection?
I’ll appreciate any help!
Many thanks!

You posted a question on one of my threads from a couple years ago, but now your post there seems to be gone, or I can’t see it anyway. So I’m responding here.

In the end my Drobo needed replacement. My UPS failed to protect it, and the UPS manufacturer stopped responding to my attempts to claim on their so-called $1M equipment guarantee which in the end was worthless. So I had to pay for a new Drobo but fortunately my data was OK in the end.

I know this may be old. I have purchased a Used 5N with the same Yellow power light. I also read out the serial port. I have this:

Initializing PMU…
Reading PMU Version…
PMU Version: 0.0.0x0000, Failsafe Version 3 (Variant 0x000)
Considering an Update to the PMU …

**** WARNING: PMU is currently running in FAILSAFE mode - limited functionality until it is reprogrammed ****

Unit will be reprogrammed and rebooted due to PMU in Failsafe mode
PMU is now in Failsafe Mode…Starting S-Record Dump:

Anyone know where the PMU is or what it is? Is it a chip or is this software? I also removed the battery and measured the battery. Its 0.5v Supposed to be 3.6-4.7 or so. I suspect the battery charging circuit may be part of this PMU business?