MP2 Improvements.

[Bryce]

Hi all,
     I've mentioned several times in the past about the failings of the MP1 and MP2 modulator circuitry. The main reason that the picture quality was so bad was because of the cost cutting that Alan did, namely, they decided to leave out the delay line (a relatively expensive part) and some filtering.

This morning, I was clearing out some stuff and came across a box of Amiga 520 expansions. This was the modulator that came with the Amiga A500 to give Composite video and UHF outputs from the monitor port. They were also based around the Motorola MC1377P that the Amstrad MPs used, but they did it properly and didn't cut corners. So this week, I'm going to wire one up to my CPC and see if the picture is any better, or whether Alan was right to have made the savings.

The Amiga 520 PCB is probably small enough to fit inside the MP case, so if it does give a much better picture, it may be an easy way to pimp your MP and give it a last chance.

I'll post my findings as soon as I have something up and running.

Bryce.

[Gryzor]

Heh, who would've thought, modding a mundane ancient add-on

[Bryce]

Me. Well I probably wouldn't normally, but I found them and was short of something to do. Also someone asked recently about getting a composite signal from a CPC, so I still had it in my mind.

If it works out, it could actually be useful to someone, especially as the 520 can be found for pennies because most Amiga A500 users have one, but don't use them.

I've just removed the 23way connector to make direct connects, but the rest will have to wait as I've been told that I'm going out for a walk as the sun is shining. 

Bryce.

Edit: Now that I've opened it up, Amiga also saved a bit. That's not a real delay line either, but it's a better solution than the Amstrad one.

[Gryzor]

You're right, I think I've also got a 520 somewhere, though it'd probably be easier to get a new one

Regarding it not being done 'properly' either, maybe there are different models?

[Bryce]

You're right, I think I've also got a 520 somewhere, though it'd probably be easier to get a new one

Regarding it not being done 'properly' either, maybe there are different models?

I'll open another one later to see if it has the same delay solution. The PCB has the footprint for a proper delay line instead of that "pregnant hybrid".


Bryce.

Edit: Well look at that. I opened up another one with a much earlier serial number and it has a real delay line installed. It also uses a slightly more expensive PCB material and the layout has changed. For reference, the costdown 520 has the serial number 127261 (Made in Taiwan), the delay line version has the serial number 003758 (Made in Hong Kong). I'll use the delay line version for the experiment.

[GUNHED]

Hi all,
     I've mentioned several times in the past about the failings of the MP1 and MP2 modulator circuitry. The main reason that the picture quality was so bad was because of the cost cutting that Alan did, namely, they decided to leave out the delay line (a relatively expensive part) and some filtering.

Just out of curiosity... How much money do they save in production by leaving these parts away.
And how much difference in the cost for the consumer would it be?

[||C|-|E||]

I am very intrigued about the results, to be honest.

[VincentGR]

I am very intrigued about the results, to be honest.

Same here

[Bryce]

Just out of curiosity... How much money do they save in production by leaving these parts away.
And how much difference in the cost for the consumer would it be?

Good question, but quite difficult to say. It's not just the cost of the actual component itself, but also the time/cost taken to fit it, the cost of storing the part etc. It wouldn't change the end price to the consumer, but it could have possibly added maybe a $1 in profit. Cost saves never change the consumer price, that was already decided before they started designing the device.

I've another project to finish first this morning, then I'll wire up the modulator.


Bryce.

[SkulleateR]

Now this could be interesting ... Should have some of those A520 stored in the basement 

[CFox]

This is interesting, although I can't personally find any use for working RF/composite modulator for CTM monitor.

Little offtopic, but I'm curious though that does anyone know what resolutions and refresh rates CTM640/644 supports? You can basically very easily input other RGB or composite signals to Amstrad monitor and thus use it as a CRT replacment for other retro systems. I'm pretty sure that it is 50Hz maximum, but has any one tested how it handles different resolutions and systems like old consoles or other computers?

[Bryce]

If you have a CTM, this project will be of no interest to you, but if you only have a composite input on your TV, then it could be useful.
As for the CTM resolution, I'd also guess that 50Hz will be it's limit, but I've never tested it or checked if there are any components that wouldn't handle that.

Bryce.

[Gryzor]

This reminded me of the time I fed an episode of Game of Thrones through an MP2 to my CPC monitor. It looked glorious

[Bryce]

Thenks for the Thread reminder @Singaja . This experiment had been pushed to the back of the bench, ready to be forgotten. Maybe I'll wire it up today.

Bryce.

[tjohnson]

Thenks for the Thread reminder @Singaja . This experiment had been pushed to the back of the bench, ready to be forgotten. Maybe I'll wire it up today.

Bryce.

I've got one of these on they loft, what is a delay line and what is the component is it actually called a delay line?

[Bryce]

A delay line is a component that delays a signal by a certain amount of time (usually in the nano or micro-second range). This was originally done by sending the signal through a very long wire, but later for TV they achieved this by bouncing ultrasonic waves around inside a prism. In the A520 (in the photo above) it's the long grey box right beside the chip.

You can read more about them here: https://en.wikipedia.org/wiki/Analog_delay_line

Or Dave Jones has a short video here, where he tore one apart (cos that's what he does ):



Bryce.