Maynuo M9812 no-load hum, normal?

[ChuckDarwin]

I just took delivery of a Maynuo M9812 (cheaper than the M9712 this week).  On powering it up, I got quite an audible switching sound/hum.  A visual check of the PCB showed nothing amiss and I couldn't pinpoint the source or an offending MSOFET in particular.  Both heat sinks were humming when tested with a dowel.  Display reading are OK, although the voltage is a bit off which I will recal.  After discharging an SLA, the device is now much quieter on no-load, but there is still quiet hum.  I've had a similar unit in the past that was quiet until loaded.  Is this normal for this model, or should I be testing the drivers/MOSFETS and refastening everything?

[lbreuss]

Just got a M9710 and it had a terrible humming rattle on the transformer. 

My bad, I broke the rule, I didn't tear it down before firing it up for the first time! I apologise.

So I disassembled the transformer bracket, gave it a few slaps with a hammer, et voila, the humm is gone. Nice and quiet now. In my case, I would say that's OK for the discounted price of the M9710...

Before:  https://youtu.be/dg0al1XIGhk
After: https://youtu.be/xZ6jg4lnjkE