View Single Post
  #11   Report Post  
Posted to sci.electronics.repair
Phil Allison[_3_] Phil Allison[_3_] is offline
external usenet poster
 
Posts: 1,249
Default Use of non-screened transformer in old monitor

Jon wrote:
------------

I have partially repaired an IBM mono monitor whose mains transformer
had failed.

http://minuszerodegrees.net/oa/OA%20...y%20(5151).pdf

Driven from a genuine PC of the day which drives another such monitor
perfectly well the picture now sort of moves around but at a rate of
1-2Hz. Turning up the brightness shows a wavy left/right edge implying
a few hundred Hz effect. But the effect is also vertical.

Note I say moves. It does _not_ contract or expand which would indicate
insufficient headroom after the rectifier before the 15v regulator.
I am happy this isn't happening.

Now I notice the original transformer was a solid metal screened thing with
an extra grounding wire.


** That tranny has a very low external 60Hz field. Besides the steel box, it may have a copper flux strap around it and use more than usual primary turns.

The rest of your post is pure, wishful thinking.

Maybe the whole 15V supply can be placed at some distance from the monitor, in its own box.




...... Phil