Cisco 9300 stack beep

[gettnbetter]

I have four 48 port POE 9300's in a stack.  One has a 2x40G QSFP+ module, and another has a 8x10G SFP+ module.  The other two switches have no modules.  Both data and power stacking is used and connected properly.  The ios shows the data stack at 480 and the power stack as ring.  There are no environment issues when i do a sh env all, all status is OK and or healthy within tolerances.

Problem is, shortly after the switches boot, one starts beeping constantly.  It's a constant whine, not fan noise.  If I unplug power from the beeping switch, another starts beeping.

I have tried the supplied power supply in the first slot of all switches, no effect, still beeps.  I've tried the second slot of all switches, same thing.  I've tried populating all power supply slots with power supplies and the same thing happens.  I've tried swapping fans, all are green.  All power supplies show green.  All the lights on the front of the switches are green.

I make a stack of two switches with the same power and data stacking, one PS or four, no beeps.  Adding two more starts beeping.

Is this normal?  Is there some command I am not aware of that might show what the constant beep is?

[Reza Sharifi]

What if you plug in all switches to a PDU or wall outlets with no power stacking at all?

HTH

[gettnbetter]

Thanks for the reply.  Removed all stacking cables and the beep still occurred.  I finally moved the switches to another bench and noticed the beep stayed at the workbench.   Not related to Cisco at all.  Was a hidden UPS under the test table whining about too many amps.  Didn't know it was there.  Adding the 4'th switch or more power supplies added to the problem which makes sense now.  Was difficult finding the source of the noise.

I guess I can claim I still have yet to hear a Cisco beep which is a good thing, I thought I was going crazy.

[Reza Sharifi]

So, it was a UPS and not a Cisco switch issue. Glad you found the problem.