Ai prime making a buzzing noise

Steelerfan747 · Apr 24, 2018

Hey all. Picked up a used prime (non hd) and if I run it below 40% - 30% it makes a buzzing noise yet it does not do it when running at 100%. This is my first prime but it does not sound normal to me. Anyone else experience anything like this? Hoping it goes away as I have it in my work office and if it does not I may end up having to buy a new one.

Dr. Reef · Apr 24, 2018

could it be the fan running as less RPM making noise and a higher RPM not.

oreo54 · Apr 24, 2018

Capacitors and/or inductors can "buzz". Probably was always there..

overclockwise · Apr 24, 2018

You're probably hearing the driver's PWM dimming. If you wave your hand under the light at different speeds, do you see a strobe effect?

Steelerfan747 · Apr 24, 2018

Dr. Reef said:
could it be the fan running as less RPM making noise and a higher RPM not.

If I shut the light off, the buzzing stops even though the fan is still running

Steelerfan747 · Apr 24, 2018

overclockwise said:
You're probably hearing the driver's PWM dimming. If you wave your hand under the light at different speeds, do you see a strobe effect?

What exactly is the PWM? Not sure on the strobe effect. Just tried it today for the first time and was not checking for that. It’s my work tank and I am off tomorrow so my next chance to try it will be on Thursday

oreo54 · Apr 25, 2018

PWM = pulse width modulation..
LEd's are (currently) normally dimmed by cutting the current off in abrupt steps.
Means the LED sees either full current or none..(simplification).
So at say 50% it has full current 50% of the time and zero current 50% of the time.. so it "appears" dimmed..
Picture of output on/off cycle.

Generally the frequency (number of cycles per second) is around 500Hz.. Normally above human detection.. Unlike old fluorescents at 60 -ish cycles per second (normal pulse not dimming).

But getting back to the point, in a circuit once in awhile due to a bad/incorrect part and/or poor mounting and the design a component can flex or vibrate itself or the circuit board and IF it's is in an audible range you can hear it.

The vibrations could be present in brighter setting but move to the inaudible range..

You would need to pinpoint the source.. either power supply (believe separate) or drivers (believe on a board inside) and fix or replace it.

Think of it that somewhere your electronics is acting like a speaker and vibrating it to produce sound you can hear.
Capacitors are one source.. Chokes/coils are another
https://www.murata.com/en-us/support/faqs/products/capacitor/mlcc/char/0020