Date   : Wed, 07 Nov 2007 07:48:45 +0000
From   : mike@... (Mike Tomlinson)
Subject: Different monitor specs...

In article <47303691.3040108@...>, Kris Adcock
<beeb@...> writes

>On the subject of Cubs ... am I the only person who is very bothered (to 
>the point of nausea) about the noise they make?

No idea :)

> I've had lots of these 
>(I had a collection of nearly 30 at one point, because I had an idea 
>about making a video wall, or novelty hamster cages) and they have ALL 
>made such an irritating whine

They're based on a classic design (old at the time of their manufacture)
in which the line voltage for the tube is generated by a circuit that
produces 8kV, which is then tripled to 24kV using a tripler module.
This uses more wound components (coils, transformers) than modern
designs, and those tend to vibrate.  The metal housing doesn't help - I
think it makes the whine echo - and the board is held by its edges on
standoffs on the bottom of the case, so that vibrates too.

Modern TVs and monitors generate the high voltage using a device called
a flyback, which has its coils "potted" (immersed in epoxy) which helps
to reduce vibration noise, but not line whistle, obviously.

Microvitec did make some Cubs using a revised design (series 4 PCB) with
a flyback.  They were very unreliable though.  I suggest monitors with
the model number 1431-MS4F are best avoided.

M.

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