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General Category => Amstrad CPC hardware => Topic started by: ced64k on 12:00, 10 September 17

Title: CTM 644 vs CRT TV
Post by: ced64k on 12:00, 10 September 17
To save space I'm thinking about keeping only my 2001 21" Philips CRT TV for retrogaming.

(http://stereo.ru/before/images/profile/151/img_med0.jpg)

I was wondering about the image quality vs an Amstrad CTM 644. Is it worth it to buy a scart rgb cable and power supply ? What do you think ?
Title: Re: CTM 644 vs CRT TV
Post by: ||C|-|E|| on 16:10, 10 September 17
Well, the Philips is going to be probably better in terms of image quality. It happens that the CTM 644 is nothing special, mostly a cheap color TV with RGB input and no tuner. I like to repair, keep and use original Amstrad monitors, but it is for nostalgic reasons...
Title: Re: CTM 644 vs CRT TV
Post by: roudoudou on 16:30, 10 September 17
CTM644 does not have distortions like TV-CRT, especially like Philipps, Sharp and even Sony
Title: Re: CTM 644 vs CRT TV
Post by: ||C|-|E|| on 20:28, 10 September 17
CTM644s have purity problems, shadowing, are very sensitive to magnetic fields...  :) Distorsion is not heavy, although I have seen it too. DonĀ“t get me wrong, I like them, but they are far from being really good displays. However, I must admit that they are quite robust  :)
Title: Re: CTM 644 vs CRT TV
Post by: tjohnson on 20:33, 10 September 17
I would have though it would be worth a try see what the picture quality is like and decide if you want to stick with the Philips.
Title: Re: CTM 644 vs CRT TV
Post by: ced64k on 13:53, 04 October 17
I received the din to scart cable today. I have strange black pixels moving on top of the screen. The cpc is powered with the CTM644, I'm waiting for external psu. This tv is working nicely with other RGB game consoles. Any idea ?

(https://i.imgur.com/D4RwVb8h.jpg)
Title: Re: CTM 644 vs CRT TV
Post by: Bryce on 14:06, 04 October 17
How long is the cable? And have you cleaned the monitor socket pins lately?

Bryce.
Title: Re: CTM 644 vs CRT TV
Post by: ced64k on 14:14, 04 October 17
The cable is only one meter long.

I noticied there is no problem at beginning. After 1-2 minutes the blacks pixels appears and take more and more place on the screen.

Here's a video:

https://www.youtube.com/watch?v=3J3NXHWwYTs
Title: Re: CTM 644 vs CRT TV
Post by: Bryce on 15:02, 04 October 17
And you're 100% sure that other retro computers/consoles connected via SCART don't exhibit this? That looks to be a problem with the TV, not the cable.

Bryce.
Title: Re: CTM 644 vs CRT TV
Post by: ced64k on 15:11, 04 October 17
Yes, Megadrive RGB for example:

(https://i.imgur.com/E6IKBeSl.jpg)
Title: Re: CTM 644 vs CRT TV
Post by: Bryce on 15:14, 04 October 17
Does the cable have any components in the SCART connector? How is it wired?

Bryce.
Title: Re: CTM 644 vs CRT TV
Post by: ced64k on 15:57, 04 October 17
Here it is :)

It's a cable from ikonsgr74 on eBay.

(https://i.imgur.com/TKyF4AJh.jpg)
Title: Re: CTM 644 vs CRT TV
Post by: mr_lou on 16:51, 04 October 17
I would also say that a CRT TV generally gives a better picture than the CTM644. But not all.
I tried a lot of different TV's before finding one I was satisfied with, and it was a Philips.
Title: Re: CTM 644 vs CRT TV
Post by: chinnyhill10 on 17:38, 04 October 17
Quote from: roudoudou on 16:30, 10 September 17
CTM644 does not have distortions like TV-CRT, especially like Philipps, Sharp and even Sony


They do have distortions in line with cheap portables of the period. You don't tend to see the worst of it as these problems usually occur on the edges and the CPC has a border. Screening isn't great either so if a magnetic field gets anywhere near them you can end up with permanent distortion.


A CTM monitor is just a cheap TV tube in a custom box with RGB input. Nothing special. Even on the CPC's release the press noted that the colour monitor struggled in 80 column mode and that was just from seeing the machine at the launch!


Got an Acorn CRT here (rebadged Phillips) of roughly the same vintage (1989) as many CTM's. Whole different beast. Just better in every single way.
Title: Re: CTM 644 vs CRT TV
Post by: ced64k on 22:11, 04 October 17
Weird update:

I get a perfect image with this switch  between the tv and the cpc :

(https://i2.cdscdn.com/pdt2/1/0/2/1/300x300/auc5019318042102/rw/selecteur-video-peritel-rca.jpg)

But only if the Megadrive is also plugged to the switch and... power on  :o


If I unplug the Medadrive the image become b/w, same effect as if I didn't push the RGB button on the switch.

It's stange because if I remember there is no electronics in this switch.
Title: Re: CTM 644 vs CRT TV
Post by: Bryce on 07:29, 05 October 17
Sounds like you have a floating ground. Can you solder?

We can try something out, but first check whether the brown wire is properly soldered at both ends.

Bryce.
Title: Re: CTM 644 vs CRT TV
Post by: ced64k on 07:35, 05 October 17
Quote from: Bryce on 07:29, 05 October 17
Can you solder?
I managed to solder a GPIO header on a Raspberry Pi Zero and against all expectations it works, so I will say yes  :D :D
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