after rubber now peeping

[Jeroen Proveniers]

> -----Original Message-----
> From: Martin Czech [mailto:czech at Micronas.Com]
> Sent: Friday, August 25, 2000 12:02 PM
> To: synth-diy at node12b53.a2000.nl
> Subject: after rubber now peeping
> 
> 
> After fixing the keys I'd like to fix noise:
> 
> Most fluorescent displays have some peeping or squeaking
> noise, I guess due to hf transformer for the background
> light.

Fluorescent display don't have backlighting. It works in fact like a tube.
The filaments emit electrons, which are attracted to the grid and then to
segments. The segments have fosfor on it that lights when the electrons hit
it.

> This seems to be acoustical emissions from the trafo coil.

It can be the trafo, or the display itself. The filament wires are mounted
on little springs to keep it tensioned. This makes a perfect string I think.
When you tick display softly which a screwdriver you can hear the filaments
resonate, like a tuning fork.
Maybe changing the operating frequency of dc/ac converter stops the
filaments of resonating. 

If it's the trafo, coating it makes it mechanicaly stable.

JJ