Amstrad CTM644 to other devices

[TFM]

Can you adjust the Height & Width of the screen on ths monitor at all?

Yes, you can, and I did that for some monitors. You find the needed potentiometers inside the monitor, so you have to unscrew it and get the plastic shell off (temporary). I once did that to adjust a monitor in a way that a circle in mode 2 is really as high as wide.

[Bryce]

Turning those potentiometers too far can badly damage or seriously shorten the life of the monitor. I wouldn't advise it, if you are not 100% sure of what you are doing.

Bryce.

[TFM]

They wouldn't have included it, if there wouldn't be sense for them. Else they could have just used resistors with one constant value. And as we know Amstrad did things always with having low cost in mind. I saw no problems using them. But hey, sure, you can overdo everything 

EDIT: More expansive monitors have the same potentiometers outside.

[Beaps]

I looked on the monitor mobo, I couldn't see any pots to turn for hight/width.

It's a shame they didn't include this feature as the borders are rediculas

[TFM]

Hmm, my CTM644 has that stuff and also my Plus monitor.

[Bryce]

@Beaps: They are definitely there, usually on the PCB that's plugged onto the tube.

@TFM: Yes they are definitely there for a reason, but not that reason that you suggest. They are there because the entire circuit is analogue and every component has tolerences. You have to have variable components to tune the circuit. No two analogue circuits work identically, the variable resistors are there to make them at least similar.

Bryce.

[Gryzor]

I would think the width is pre-set, but I used to adjust the height by placing big books under it.

[Bryce]

The width (screen to border ratio) is determined by the signal sent from the CPC, but you can widen the screen part by adjusting the monitor to scan wider than the physical screen, you are just hiding more of the border off-screen. The scan voltage is produced by an analogue circuit, so it can vary quite a bit, the variable resistor is there to tune the voltage to the screen size. If you raise this too much, you could overload the deflection coil or other parts that aren't spec'ed to take such a high voltage.

Bryce.

[TFM]

Well, I got a similar monitor - I mean similar to the CTM644, but it's more like a kind of multisync monitor. That one has the same potentiometers outside, which the CTM644 has inside.
These "inside" potentiomers of the CTM644 (IIRC) are NOT the small ones used for justification of things on the PCB, they are indeed bigger. Therefore I was able to find them 

However, it really doesn't matter.