The Schneider / Amstrad CPC in the USA - means 60 Hz and 110 Volts

[TFM]

Hello Lady and Gentlemen,

Here I want to post my experiences with the CPC in the USA. A while ago I managed to buy a CTM644 at eBay USA which was made for the us market. Then I brought over a CPC6128 keyboard from Germany to set up a CPC workstation which finally happened yesterday. Now I want to tell you about my results...

The CPC6128 has a 50 Hz / 60 Hz switch. And both modes run well with the CTM644 connected to a 60 Hz / 110 Volt power network. Actually both modes look nearly the same on the screen.

When using FutureOS then a third of the upper icon raw is missing and also the messages in the lower line are hard to see. Well, I don't know if this is an effect of the 60 Hz power network or if the previous owner of the CTM644 did manipulate it (I remember you can change a lot of things internally, I will take a look at it soon).

Sadly I can (at this moment) not provide pictures, but I will try to catch up with that.

If you like to comment please stay on topic - I will try to regularly update this thread with new information.

[TotO]

Nice to know that.

[Bryce]

Na, that's because the CPC is sending the screen data too slow. Move the jumper in the CPC and your top/bottom rows will be visible again. I doubt anything has been changed in the monitor.

Bryce.

[TFM]

Please read careful. As told I tested the CPC with 50 Hz and with 60 Hz. My bet is clearly the monitor, but if somebody else can tell different we will know. Since I don't like this thread to become a pure gossip thread like 90% are, I have to add some new information...

The US CTM644 is obviously strong enough to provide enough power for the CPC6128 and a connected Mother X4 with three cards (X-MEM, PlayCity and Mini-Booster). That's a relief. 

[Bryce]

Ah, ok, I mis-understood your post. Then the H-Pos just needs to be tuned a bit.

Bryce.

[TFM]

Yes, right, the button at the back of the monitor. No need to open the CRT case.


Actually it looks like that most commercial games are running well. However it looks like the screen is a bit stretched in Y (less scan lines). But at told maybe the monitor was manipulated. Would be great to find a second US CTM to compare them. Meanwhile I leave it like it is and try to perform more testing.

[ralferoo]

Actually it looks like that most commercial games are running well. However it looks like the screen is a bit stretched in Y (less scan lines). But at told maybe the monitor was manipulated. Would be great to find a second US CTM to compare them. Meanwhile I leave it like it is and try to perform more testing.

That's to be expected - the discharge capacitors that provide the Y deflection voltage will be timed to go from top to bottom in 16µs, for PAL it'd be 20µs.

The discharge rate is different from the flyback, which is affected by the VHOLD knob on the back of the monitor - this changes the free running rate of the clock. You will probably be able to find a setting that works for both 50Hz and 60Hz modes (as it sounds like you have) as it just needs to be close enough that the PLL can react to the VSYNC signal.

So, the top will be aligned correctly, but the picture will sweep down the screen quicker than on a monitor set up for 50Hz, hence why the bottom lines are missing.

I haven't tried it, but from the 464 schematic on the CTM 640 the variable resistor VR406 (labelled Y size) should change the vertical discharge rate - it's just slightly diagonally in from the top right of the picture of the PCB on page 22.

Of course, you probably don't want to get an ultra rare US CTM just to configure it to work in PAL mode!

[ZbyniuR]

As I know connect LK4 makes any CPC to send picture NTSC.

LK Links - CPCWiki

Picture look then higher and more square and sprites blinking funny.

Maybe in USA version this is connected and if you cut this LK4, picture became normal PAL.

[ralferoo]

As I know connect LK4 makes any CPC to send picture NTSC.

This only affects BASIC and games that don't reconfigure the CRTC (so possibly quite a lot of early titles).

It actually changes VTOTAL, VSYNC and VADJ. Potentially anything that only changes horizontal size and/or VDISP (Speccy ports) might work too, but as soon as VSYNC is changed to centre the picture if VDISP is changed, the picture would mess up (either the top cut off or loss of vertical sync) depending what it was set to.

[SyX]

This only affects BASIC and games that don't reconfigure the CRTC (so possibly quite a lot of early titles).

Exactly, i made a few tests some time ago and the number of games working is a lot.

For testing, before to launch a game, you only need to write:

Code Select Expand

OUT &BC00,4:OUT &BD00,&1F:OUT &BC00,5:OUT &BD00,4:OUT &BC00,7:OUT &BD00,&1B
And then you will need to touch the vertical synch in your CPC monitor or if you have your CPC attached by scart then the TV will select the NTSC mode automatically (or you need to press a button in your remote).

I get a crash in AMC, but with the other games that i tested, i got better results (or was the placebo effect ), mainly the music goes faster and the games are a little smoother, if i remember well, i tested Fernando Martin, Bomb Jack, Commando Quatro, Comando Tracer , Megaphoenix (this really looks better),  ...

Then i put a thread in the spanish forum for other people could try in real machines, but i didn't get any aswer

[TotO]

As, it is possible to use a 60Hz configured CTM on a 220 Volts country, it is possible to use a 50Hz configured CTM on a 110 Volts country. Many peoples does that since more than 20 years with video games consoles, without problem and most TV support 50/60Hz. The same about your old PC CRT monitor that handle from 60Hz to 85Hz (sometime more) on any country.

The CPC programs was mainly done for Europe and 50Hz display... So... Use 50Hz !
That will not destroy anything, while you respect the country voltage.

About CTM displaying 60Hz instead of 50Hz, you have to understand that as a side effect for the display, by losing lines.
A 50Hz 384x288 overscan screen will be truncated to only display 384x240 at 60Hz.
You will got black borders on top and bottom of the screen, if you don't adjust the vertical monitor size.

That mean, if the CTM is already set for a 60Hz display, you should have to change manually the potentiometer inside it to restore the image heigh for matching with conventional CPC display.

In all cases, for the same screen resolution, you get more CPU time in 50Hz than 60Hz for displaying things.

[TFM]

The power supply of the CTM664 seems to be weaker than the GT65 in Germany. Usually the color monitors have couple AMPs more than the green screens, but in this case the 110 Volt seem to be a problem.


While I had no problems with the Mini-Booster and the X-MEM, both on Mother X4 board, it's an issue in the states.


However I may be wrong here. Keep you updated.

[ralferoo]

The power supply of the CTM664 seems to be weaker than the GT65 in Germany. Usually the color monitors have couple AMPs more than the green screens, but in this case the 110 Volt seem to be a problem.

Bryce will know better, but I suspect the 464's tape drive motor requires more power than the 6128's disk drive motor because of the weight of a full spool of tape. The monitors in Europe will have been designed to work with any CPC, the power board for the US monitor was probably only designed to be just sufficient to power a 6128.

[Bryce]

Bryce will know better, but I suspect the 464's tape drive motor requires more power than the 6128's disk drive motor because of the weight of a full spool of tape. The monitors in Europe will have been designed to work with any CPC, the power board for the US monitor was probably only designed to be just sufficient to power a 6128.

Actually the power specs were probably identical for 464/6128 on both sides of the ocean, but remember it's 30 years old. The capacitor leakage, dry joints and oxidised contacts are enough to swallow half an amp, so the monitor won't perform as it did back then. Service it properly and it will easily supply X-Mems etc.

Bryce.

[TFM]

Well... if I could I would. 

[MacDeath]

Also ocean is salted water, the crossing takes its toll.

[TFM]

Ok, so the USA CTM644 outputs 1.7 Ampere at 5 Volts and 0.4 Ampere at 12 Volts.
(That's at least what the monitor tells at its back).

EDIT: Found that the European monitors output the same Amps.
The Service manual links in the wiki seem to be dead.
CTM640/CTM644 - CPCWiki

[steve]

Yep Amstrad links still dead although I did retrieve the Schneider CTM640 manual.

[Gryzor]

Thanks for pointing it out, will take care of it.

[Gryzor]

...fixed.

[TFM]

Interesting: The Service Manual shows two PCBs for the CTM644, the main PCB and the small one at the end of the tube itself.


Now mine (US CTM644) got a third PCB. It's located vertical at the side of the plastic box. Got few parts on it, maybe a transformer or so. Have to look again...