Subject: Monitor screen width adjustment?

From: Adrian Vickers <[email-masked]>
Date: Tue Mar 4 12:43:12 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 
adjusters for focus & brightness (or maybe contrast, it was hard to tell 
since it was simply labelled "Screen". There's also externally accessible 
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). 
It looks like there ought to be a green pot as well, but there's no trimmer 
there, just a fixed resistor.

So, is it the case that I cannot adjust the h.size? Is it a case of go 
rooting around looking for the component (a resistor, I assume) which sets 
this, and replace it with a pot?

Any advice appreciated.
-- 
Cheers, Ade.
Be where it's at, B-Racing!
http://b-racing.com

---

From: [email-masked] (Tony Duell)
Date: Wed Mar 5 06:03:27 2003

> 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).

> 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.
 
> there's trimpots to adjust red & blue intensity (with two pots per colour).

Probably a gain and offset control for each colour. 
 
> 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