Desk fan makes screen flicker

[grangervoldemort]

I have a 40w desk fan.

It has an analogue turn switch to turn on and change speed settings. Photo:

 

 

I currently have two displays. An old Dell 1703FTP and a Samsung P2450h from 2010~.

 

The Samsung flickers when I change speed in either direction and when turning on. The screen shows 'HDMI' after it recovers from the flicker on/off.
It ALSO causes my speakers to make a kinda pop sound.

 

There are 2 types of flicker that happen. One is juddering of the image on screen.

 

The second is the display is lost with a flicker, then a second or so later comes back again with the screen saying 'HDMI', like as if it only just detected the input.

 

I can also dictate which type will happen for the most part. If I turn the switch on the fan slowly then the second type of flicker occurs (loss of display for a second or so).

 

The Dell display is unaffected by this.

 

Why is the Dell not affected?

Why is this happening to the Samsung screen?

 

I tested it with 2 other fans. One has a digital control (a digital on/off switch with a bunch of other buttons for various modes and functions), and the other has the same type of analogue switch present on my fan.

 

The digital fan causes no flickering at all AND no speaker pop sound.

The other analogue fan causes the EXACT same issues only even more juddering and the speaker pop sound.

 

Speakers are Logitech Z5500.

 

Digital fan

 

Other analogue fan

 

EDIT: Tested on another socket in my room (same room) and the same issue occurs.

[Rainbow Dash]

Check if the fan power cables are touching any other cables. I think it could be some interference.

[grangervoldemort]

39 minutes ago, Rainbow Dash said:

Check if the fan power cables are touching any other cables. I think it could be some interference.

What.... Did you read the entire post? Tested with other fans too. Fan cable was not touching the speaker nor screen wires.

[Rainbow Dash]

3 minutes ago, grangervoldemort said:

What.... Did you read the entire post? Tested with other fans too. Fan cable was not touching the speaker nor screen wires.

I read the whole post, I was thinking that specific fan was causing interference.

[grangervoldemort]

Just now, Rainbow Dash said:

I read the whole post, I was thinking that specific fan was causing interference.

Then you did not read the entire post.

[mariushm]

The Samsung's power supply has less AC filtering inside so it doesn't reject the noise introduced in the mains wire by the fan. Also, the Dell's psu may be overbuilt, better than Samsung's... they made them cheaper as time went by.

Also, the monitors of that time are known to use bad electrolytic capacitors which slowly go bad over time. The power supply could already be unstable but just good enough to work right but maybe it goes over the edge with the extra noise added by the fan (so it's like the monitor resets itself due to power loss).

 

Your Samsung monitor will be very similar inside to the monitor in the video below, the power supply inside will also be very similar...

Would be worth opening your monitor to inspect the capacitors and maybe replace them with proper low esr quality ones if you're not afraid of a soldering iron.