Sync level of 6128+? ***SOLVED***

[emuola]

I'm having a hard time getting a 6128+ to be hooked up to a scart (rgb) - vga scaler/converter. With MSX/TG-16 the converter works great, but with 6128+ both of my displays (24" Benq and Sanyo PLV-Z700) cannot get the sync correctly. The same scart cable delivers a superb picture to a crt telly, so the cable is ok. I was wondering if someone would know the sync level (or what is it called, I mean the voltages) of a 6128+? I have a multimeter, but I'm afraid I'll break something 

[Bryce]

If the sync is jittering, then it's usually the frequency that's off, not the potential.

Bryce.

[emuola]

If the sync is jittering, then it's usually the frequency that's off, not the potential.

Bryce.

Thanks again Bryce Would this explain why the crt telly likes the signal but the converter doesn't? What exactly does jittering mean here? Is there something wrong with the Plus? Is it possible to correct the jitter?

[Bryce]

The jitter usually causes the display to flicker every few seconds or in the worst case, the picture is completely distorted. This is caused by the frequency being outside the acceptable range that the digital converter is expecting, so it keeps reseting the sync. There's not a lot you can do about it unfortunately. I use a V2V converter with my plus and it works fine, but the same converter flickers every 5 or 6 seconds with all Commodores.

Analogue CRTs don't have this issue, they produce their picture sync signal from the input sync, so they display whatever you send it (within reason).

Bryce.

[emuola]

Thanks for the explanation. However, that's what I was afraid of. It seems impossible (or at least not econimically feasible?) to get all my retro computers hoked up to the projector/lcd via scart (rgb). Amiga 1200 has a sync problem also, because it has a ttl level sync signal (~5v). Of course that's easily corrected with a few resistors. On the Amstrad side of things, I don't know what t do. I guess I should get one of these babies:

XRGB-3 - XRGB wiki

But the prices are something like 400€...

Is this really this complicated/expensive?

[Bryce]

I (and many others) also use this type: Arcade game RGB/CGA/EGA/YUV to VGA HD video converter board 1 VGA output | eBay

It lacks a case, but for €27 it's a fantastic piece of hardware and works with many 8-bit computers. It also only needs a simple 5V supply.

Bryce.

[emuola]

Ah, I had completely forgotten that piece of hw. Actually it's still in my watch list in Ebay, but it's been a while since I've logged in. I think I'll order one anyway and see how it can handle the different kinds of signals We'll see how it goes!

[emuola]

Ordered one of those.

Arcade game RGB/CGA/EGA/YUV to VGA HD video converter board 1 VGA output | eBay

I ran to this little gadget while reading about scanlines. Could be useful for someone here

http://wp1114205.wp150.webpack.hosteurope.de/xtcmodified/product_info.php?products_id=15

[Bryce]

Interesting little device. They semm to be using an LM1881 to remove CSYNC signal completely and then insert a new properly timed CSYNC. I'm not sure if this would work on a CPC, but I have a few LM1881 lying about somewhere, maybe I'll give it a go and see what happens.

Bryce.

[emuola]

Ok, please report if you get interesting results

The Scanline generator could also be nice:

http://wp1114205.wp150.webpack.hosteurope.de/xtcmodified/index.php?cPath=3

I was thinkin to put that between my Matrox Mg450 and 21" Hitachi crt in my Mame cabinet    But of course would be suitable also for "imitating that crt look" with cpc:s on moderns tv:s.

*edit*

This could be even better:

http://wp1114205.wp150.webpack.hosteurope.de/xtcmodified/product_info.php?products_id=43

[emuola]

Ok, the "cheapo" rgb to vga -convetrer arrived yesterday. I made a cable for connecting it to my scart switch (scart-male -> the 8pin rgb connector on the pcb). Now I got picture from the Plus,  but is was a bit flaky. It looks like the image "jumps" one line up or down every now and then. Ok, that's progress compared to the other solutions, but then I had also some problems: For some reason, the converter cannot display the image from my msx and Amiga?! With msx the image rolls/no sync... and with Amiga nothing. I have all the computers hooked up to the active scart switch (Keene electronics, should be pretty good) and then the custom cable from the switch to the converter. Needless to say all the hw works flawlessly on my crt telly. Also as I mentioned earlier, the other converter that would not display the Plus properly worked fine with the msx. I'd really prefer only one converter "before" the projector, but it seems it's impossible.

[Bryce]

You're problems aren't with the converter, it's the Projector that's not suitable for 8-bit signals.

Bryce.

[emuola]

You're problems aren't with the converter, it's the Projector that's not suitable for 8-bit signals.

Bryce.

I also suspected that, but this also happens with my Benq 24" lcd monitor. Unfortunately I don't have any crt monitor available atm. I was under the impression that it wouldbe possible to use a standard modern lcd (be it a projector or a monitor) with these kind of adapters/converters. Or have I succeeded in getting me 2 incompatible ones?

[Bryce]

You've succeeded in getting two incompatible ones, but that's not that difficult because many modern displays are incompatible. They tend to work better using the S-Video input instead of the RGB though.

Bryce.

[emuola]

You've succeeded in getting two incompatible ones, but that's not that difficult because many modern displays are incompatible. They tend to work better using the S-Video input instead of the RGB though.

Bryce.

Ok, da*n I guess you're right there, because my projector actually gives a very impressive image (considering the enormous scaling), when I connect my C64 to it via s-video It's a shame that I cannot utilize the scart switch fully (only with the crt telly). I could try to make a cable from the scart switch to the Amigamaniacs s-video adapter, but that adapter also had some trouble with the Plus/sync...

Is there anything I could try instead of getting me a new projector (too pricey...)? What exactly is the reason for the incompatibility (if any general reason exists)?

Sorry for being so stubborn here, but it just seems odd that you cannot get the signal converted universally (to let's say vga) from a rgb source. But I really don't understand anything about the "internals" of a rgb signal

[Bryce]

The Amigamaniac device definitely shouldn't have a problem with the Plus sync! It's based on the AD724 which should have sorted the sync issue. One question: Are you supplying the adapter / converters with the same voltage source as the computer connected? If not, this could be causing issues. Also: How long is the cable from the CPC to the converter and converter to Projector? These need to be kept relatively (under 5 Metres) short.

Bryce.

[emuola]

The Amigamaniac device definitely shouldn't have a problem with the Plus sync! It's based on the AD724 which should have sorted the sync issue. One question: Are you supplying the adapter / converters with the same voltage source as the computer connected? If not, this could be causing issues. Also: How long is the cable from the CPC to the converter and converter to Projector? These need to be kept relatively (under 5 Metres) short.

Bryce.

We discussed that adapter a while ago and Nathan did not have any clue, why the image is perfect for a few seconds and then "breaks" at the top.  I actually used a 9v psu (regulated to 5v on the pcb) when I ran the tests. Unfortunately I already "cannibalised" the cable for other projects, so I'll have to build a new one (this time from the scart switch to the s-video adapter). I'm away in a conference for a couple of days, but I'll make the cable on Saturday/Sunday. The cables have been under 2 m, so that's not the issue I guess.

[emuola]

 I made a scart to s-video adapter cable. Results are as depressing as before. No proper picture. Even my crt telly (it has a separate s-video input) does not like hte signal. The colours are very good/vibrant, but the image rolls/shifts all over the place. Nathan's adapter has this little trim potentiometer, but adjusting it does not help. Here's how I connected the pins (sorry about the horrible picture...):

Have I made some general  mistake here or what?

[Bryce]

That's still an RGB connection, not S-Video.

Bryce.

[emuola]

That's still an RGB connection, not S-Video.

Bryce.

Sorry, but I don't understand what you mean  Isn't the purpose to create a cable for connecting a rgb source to the s-video adapter? The header on the Nathan
's version of the adapter is like this:


So, I wired the corresponding pins from the scart (rgb) to the pcb (r,g,b,0v,c) and of course the +5-12v.

Is there a misunderstanding here or what  I thought that the point was to make a cable like that, but apparently I misunderstood something here?

[ralferoo]

You want an RGB SCART lead which has R, G, B, sync and ground. An S/video lead has luminance, chroma and ground.

To get your RGB lead working, you'll want to apply 1-3V across pin 16. Bryce has a solution that gets this from the sync signal during the non-sync parts of the signal. This and other possible wiring diagrams are at TV SCART cable - CPCWiki - The Ultimate Amstrad CPC Community & Encyclopedia!

EDIT: You're also grounding pin 17 which sync ground. You probably also want to ground 5,9,13 (video grounds) and 14 (blanking ground).

[emuola]

You want an RGB SCART lead which has R, G, B, sync and ground. An S/video lead has luminance, chroma and ground.

To get your RGB lead working, you'll want to apply 1-3V across pin 16. Bryce has a solution that gets this from the sync signal during the non-sync parts of the signal. This and other possible wiring diagrams are at TV SCART cable - CPCWiki - The Ultimate Amstrad CPC Community & Encyclopedia!

EDIT: You're also grounding pin 17 which sync ground. You probably also want to ground 5,9,13 (video grounds) and 14 (blanking ground).

The source is a rgb scart switch (scart female), so I shouldn't need the 1-3v on pin 16, right? I mean, because the source signal is rgb and I just make the cable to get that rgb signal to a rgb-s-video converter, so I don't have to "activate" the rgb mode?

The grounding tip is actually very good, that may very well be te reason. I suppose I just wire all those grounding pins together?

Sorry to be this dumb again. I hope you guys have the patience of a saint

[Bryce]

Correct, for the adapter cable to the converter, you don't need to activate anything. And as Ralf pointed out, you were confusing the terms slightly by saying S-Video, that's a completely different type of signal.

Bryce.

[emuola]

Correct, for the adapter cable to the converter, you don't need to activate anything. And as Ralf pointed out, you were confusing the terms slightly by saying S-Video, that's a completely different type of signal.

Bryce.

Ok, nice to know I got something right Now I understand what Ralf meant I try to do the grounding trick and see what happens.

[emuola]

Adding the grounding pins for the colours/blanking does not correct the situation This is slowly driving me nuts. It should be very simple, but it apparently is not. I tested the s-video adapter with my Amiga (it was originally made for that, so it has the connector ready) and it works. So, something with the rgb scart is not working. It's  not the switch either, because  my msx has a native scart (rgb) and it works as bad directly as via the switch.

*edit* One thing that came to my mind: With the Amiga the power comes directly from one of the monitor out pins (12v). I have a good quality atx-psu for the Amiga. With other computers I have used an external 9v (and also 5v) psu for the adapter, that probably aren't so high quality. Could this be the reason? How picky is the AD724 on the power?