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General Category => Amstrad CPC hardware => Topic started by: angelcaio on 21:11, 30 January 17

Title: Center image vertical y in a CTM-644
Post by: angelcaio on 21:11, 30 January 17
Hi, does anyone know of any definite way to center the image vertically on a CTM-64 color monitor?
With OUT & BC00,7: OUT & BD00, XX can be corrected by scrolling the image vertically, but the effect is lost upon restart or when some program resets or changes the CRTC values.
The V-HOLD knob on the back does not seem to have any effect when moving it until the image starts to jump and you have to return it to its initial state.
I searched the CTM-644 service manual but found no control for this.
Thanks in advance.


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Title: Re: Center image vertical y in a CTM-644
Post by: arnoldemu on 21:40, 30 January 17
There is something about it in the service manual "dynamic convergence adjustment".

Has it always done this and does it do the same if you connect it using a rgb cable to scart to a television?

What model of CPC is it?

Does it have indescomp international usa under the keyboard?

Is the top border always that large including in BASIC?

Do you know which CRTC it has inside?

Title: Re: Center image vertical y in a CTM-644
Post by: Bryce on 21:50, 30 January 17
Quote from: arnoldemu on 21:40, 30 January 17
There is something about it in the service manual "dynamic convergence adjustment".

Has it always done this and does it do the same if you connect it using a rgb cable to scart to a television?

What model of CPC is it?

Does it have indescomp international usa under the keyboard?

Is the top border always that large including in BASIC?

Do you know which CRTC it has inside?

Woah, don't start messing about with the dynamic convergence. This has nothing to do with the V.Pos which is what angelcaio is trying to adjust. Dynamic convergence is the setting the aligns the three colour beams with each other so that the colours converge and mix properly.

The CTM doesn't have a V.Pos adjustment, but you may be able to correct the problem by slightly increasing the V.Size (Potentiometer inside the monitor on the PCB) and V.Hold.

Bryce.
Title: Re: Center image vertical y in a CTM-644
Post by: angelcaio on 06:38, 31 January 17
Thank you. I'm going to try it


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