Monitor screen width adjustment?

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Tue Mar 4 17:56:00 2003

> Hello again,
>
> I've got a Sinclair (well, Amstrad really, but it has Sinclair printed on
> the front) monitor here, which claims to be a QL monitor. To the extent
> that it has a captive QL-specific signal lead...
>
> However, the display is too wide, and marginally extends past the bezel in
> both directions; only by about 1/4 of one character or so, but just enough
> to be seriously annoying.
>
> So, today, I whizzed the back off to adjust it - but there's no "horizontal
> size" pot :( There are trimpots for V.size, H.hold and Sub-bright. There's

You're looking for an adjustable inductor (coil) in series with the
horizontal yoke -- probably connected to the collector of the line output
transistor. OFten there are 2 inductors in series -- a normal adjustable
one (width) and one with an adjustable bias magnet (horizontal linearity).

> adjusters for focus & brightness (or maybe contrast, it was hard to tell
> since it was simply labelled "Screen". There's also externally accessible

'Screen' adjusts the voltage on the first anode (sometimes incorrectly
called the 'screen grid' in the States) and is a brightness adjustment.
 
> controls for V.hold, brightness & contrast. On the back of the tube,
> there's trimpots to adjust red & blue intensity (with two pots per colour).

Probably a gain and offset control for each colour.
 
> It looks like there ought to be a green pot as well, but there's no trimmer
> there, just a fixed resistor.

It's normal to have _one_ control (normally offset) for green, since you
don't actually need all 6 to get the right grey scale tracking. But I
don't think you can necessarily get a correct grey scale with only 4
tweakers.

-tony
Received on Tue Mar 04 2003 - 17:56:00 GMT