The Amstrad MP-1/2 and Alan's cost cutting.

[Bryce]

Hi all,
      as some of you may have read here or in the Wiki (I know I've mentioned it several times in the past), one of the things that made the MP-1/MP-2 worse than it could have been was that fact that Alan cut corners on the electronics. To be exact, he decided to leave out the delay line in the MC1377 circuit. He may also have done this because they were physically big and it probably would have made the device slightly larger. At the time, delay lines were an opto electrical device which delayed the signal by a few nano seconds by bouncing light around a glass substrate.
These days, they are incredibly difficult to find. However, I was clearing out some stuff at the weekend and found some 400ns solid state delay lines (these create the delay with MOSFETs rather than bouncing light). As far as I know, the MC1377 needed exactly this value of delay.
So out of curiosity I'm going to modify my MP-1 to how it would have been had Alan not made that decision. I'll do some before/after screenshots to see if it really makes much difference and whether Alan cut one too many corners in the name of profit. As someone who as a child only ever saw his 464 in colour via an MP-1, it will be interesting to see the results and whether Alan is the reason why all my childhood gaming was blurred

Bryce.

[chinnyhill10]

Hi all,
      as some of you may have read here or in the Wiki (I know I've mentioned it several times in the past), one of the things that made the MP-1/MP-2 worse than it could have been was that fact that Alan cut corners on the electronics. To be exact, he decided to leave out the delay line in the MC1377 circuit. He may also have done this because they were physically big and it probably would have made the device slightly larger. At the time, delay lines were an opto electrical device which delayed the signal by a few nano seconds by bouncing light around a glass substrate.

Do other computers and consoles have this? My guess is the Spectrum certainly doesn't.


Suspect it was a cost issue.

[Bryce]

No the Spectrums used a TEA2000 to convert the RGB to composite. This chip doesn't need a delay line. I can't think of any other retro computer that used the MC1377, but I'm sure there must be one or two?

Bryce.

Edit: Quick check of my notes... The Atari STFM used the MC1377, but they did it properly. How does the STFM TV picture compare to the MP-1? Anyone own both?

[chinnyhill10]

No the Spectrums used a TEA2000 to convert the RGB to composite. This chip doesn't need a delay line. I can't think of any other retro computer that used the MC1377, but I'm sure there must be one or two?

Bryce.

Edit: Quick check of my notes... The Atari STFM used the MC1377, but they did it properly. How does the STFM TV picture compare to the MP-1? Anyone own both?

Years since I've seen an MP1 but the ST has a fairly decent UHF output. Had to use it for a few days before my RGB cable arrived. It was as good as could be expected from UHF really.

[sigh]

I wonder how much money was saved from cutting this.....

[TotO]

Just open a MP-1/2 an look the PCB, to see that many electronics parts was never placed on it.
It is just an internal PSU with a bunch of resistors and voltage converter. (like done on the homebrew videocables)

[OCT]

I can't think of any other retro computer that used the MC1377, but I'm sure there must be one or two?

The Amiga did on its pluggable modulator Commodore A520 - Amiga Hardware Database - IIRC also without delay line. Similarly an external modulator project by CPC Amstrad International in a larger, more accessible layout than the MP-1 (got a populated PAL board for you to try & improve by adding a delay line if you like).

[Bryce]

Just open a MP-1/2 an look the PCB, to see that many electronics parts was never placed on it.
It is just an internal PSU with a bunch of resistors and voltage converter. (like done on the homebrew videocables)

That may be the case with the french version that was slightly different to the UK version. The UK version is fully populated as can be seen in this picture here: http://www.cpcwiki.eu/imgs/9/90/MP2_Power_Connections.png
There was never space allowed for a delay line. The PCB may look a bit crumby, one sided cheap PCB material etc, but that was quite normal for the time.

I forgot about the Amiga A520, yes it used the MC1377 too. They didn't use a proper delay line either, however, they did use a better method as an alternative delay than Amstrad did.

@sigh: I'm not sure of the exact prices of a delay line back then (that's before my time), but they wouldn't have been a cheap part, probably more expensive than all the passive parts together.

Bryce.

[||C|-|E||]

I am very curious about the results of this . I always thought that the MP-1, although quite errhm... useless today, has a nice case to put a proper psu inside . Anyway, as a kid I would have enjoyed quite a lot to have one of them just to plug the Amstrad to my parent´s big screen. Size matters  .

[fatbob]

The SAM Coupe uses a MC1377 - but then again their power supply/modulator is a badly painted & rebadged Amstrad PSU

[TFM]

Edit: Quick check of my notes... The Atari STFM used the MC1377, but they did it properly. How does the STFM TV picture compare to the MP-1? Anyone own both?

Right here the picture of the TFM is very nice and in 3D, including smooth scrolling...

Fun at side, I'm really curious about the outcome of your tests! Always thought the MP2 is pretty good, but back the day I didn't know better, had a CTM anyway (and Greeny Screeny for coding).

[Poliander]

@Bryce I found that rather interesting, any news on your modification?

[Bryce]

@Bryce I found that rather interesting, any news on your modification?

Funny you should mention that now. I was just tidying my electronics area and stumbled across the delay line chips. I've put it back on my ToDo list for the near future.

Bryce.

[AMSDOS]

I am very curious about the results of this . I always thought that the MP-1, although quite errhm... useless today, has a nice case to put a proper psu inside . Anyway, as a kid I would have enjoyed quite a lot to have one of them just to plug the Amstrad to my parent´s big screen. Size matters  .

My Dad got an MP-1 for our Green Screen 464 back in the day, which went back to the shop the next day I think, I don't even recall playing any Games with it, so it might of been a case of Switch on the computer/TV, "This is no good!", back in the box! The TV we had was 48cm, so it might of looked odd as a Computer Screen. 

[Bryce]

The main problem isn't "odd", it's more of a "blurred shite".

Bryce.

[ivarf]

The main problem isn't "odd", it's more of a "blurred shite".

Bryce.

Close to the look most other computers have that doesn't use a dedicated monitor, like the Spectrum and C64. True or false?

[1024MAK]

Well, composite video is a compromise to start with, even if done correctly. Then add in the conversion to UHF and you get an even worse picture.

A digital TTL RGB (Acorn BBC Model B, Master, Electron etc BUT only 8 colours) or an analogue RGB (as used on the CPC to feed the Amstrad colour monitors) output is far better

In rank of quality for a colour picture (best to worse):-
RGB video
S-Video
Composite video
UHF

Mark

[Bryce]

Close to the look most other computers have that doesn't use a dedicated monitor, like the Spectrum and C64. True or false?

Yes, however as many other computers used UHF as their main (only) visual output, they spent a little more time and money getting it right. So the MP1 (2) is a little more blurred and crap compared to the UHF output of computers such as the Spectrums or Commodores.

@1024MAK: Correct, but I consider RGB and S-Video to be so close to each other that I'd almost put them on the same level (if done correctly).

Bryce.

[CanonMan]

Wouldn't it be great if someone could design a drop in replacement board for the MP1/2 which featured a more modern composite or S-video converter,  and an efficient switch mode power supply.

Anyone up to the challenge?   

[CraigsBar]

Wouldn't it be great if someone could design a drop in replacement board for the MP1/2 which featured a more modern composite or S-video converter,  and an efficient switch mode power supply.

Anyone up to the challenge?   [emoji23]

Hell how about HDMI upscaling while you are at it? Scart leads work well, and are cheap. TV's that lack scart also lack svideo IMHO. So HDMI seems to be the way to go

[Audronic]

Would one of these fit Scart to HDMi


Ray

[Poliander]

Wouldn't it be great if someone could design a drop in replacement board for the MP1/2 which featured a more modern composite or S-video converter,  and an efficient switch mode power supply.

There is already a composite signal in a MP-1/2, just the plug is missing. The signal quality is not quite good, but that is where Bryce's mod comes in. On the other hand, I'll build someday a drop-in replacement board for the MP-2 with Bryce's RGB-to-SVideo circuit. (But sadly I'm not capable of "mass production")

[Bryce]

There are several solutions to put a more modern TV output inside the MP2. starting with the easiest: Composite (just add the socket), S-Video (with one of my S-Video PCBs), Other Chinese VGA / HDMI modules probably fit too. However I wouldn't touch the PSU part. It's a really robust, low noise linear supply, perfect for the CPC. Why would you want to replace that with some dodgy switchmode solution?

Bryce.

[AMSDOS]

The main problem isn't "odd", it's more of a "blurred shite".

Bryce.

Well it was perhaps that as well, which had my Dad return the MP1.

[Poliander]

Why would you want to replace that with some dodgy switchmode solution?

I meant to replace the RGB-to-composite board inside the MP-2.