Stedy's RGB to SCART cable

[Photon]

Well, 15.4" alone is unique

Would be nice to know what PAL decoder chip is in that one... it's funny how rare it is with chips that aren't crap. Well, funny haha, not funny strange - as most of the chips come from PAL-free Asia... I guess? But maybe not this chip?

[Dreamcast270mhz]

Now, all us NTSC users, who don't have scart, need to do is get a scart to component cable.

[Photon]

While we're on a depressing subject, we might talk about the SCART connector as well I've not come across a physically worse interface of any kind, to be honest. Maybe you NTSC users can consider yourselves lucky, eh?

[bebek]

Originally Posted by Photon

Well, 15.4" alone is unique

Would be nice to know what PAL decoder chip is in that one... it's funny how rare it is with chips that aren't crap. Well, funny haha, not funny strange - as most of the chips come from PAL-free Asia... I guess? But maybe not this chip?

When I will find a sec I will open it and check decoder type. I think that this LCD refresh is too slow to react on changes. It works with no flicker using Video IN too. Super Hires Interlaced is stable to but it would be nice to have it a little bit sharper and a moire is visible. Is there any hardware mod to make it sharper ? Something like removing filters on old SVGA cards? Ooops, I forgot it is no HD ready TV, will not be sharp ...

[orange]

are +12 and +5 really necessary if we're gonna use remote for RGB and aspect ratio?

[alexh]

Originally Posted by orange

are +12 and +5 really necessary if we're gonna use remote for RGB and aspect ratio?

If you're sure your TV will accept RGB input without it then sure. Not many older CRT TV's have RGB select on the remote/menu system.

[Dreamcast270mhz]

Anybody know where DB23s are sold in the states?

[Stedy]

@Bebek

The resistors are included as good practice. Those on the +5V and +12V supplies are there in case you accidentally short these pins to ground.

The CSYNC signal could damage the video decoder, the reasons are stated on the website and in the original guide.

@Dreamcast270MHz

What sort of component video do you want?

Y/C where you have a luminance & synchronisation and a chrominance signals for better colours than colour composite?

RGB video where you have Red, Green & Blue video with separate sync signals or sync on green?

Y Pr Pb video where you have a Luminance (B&W video) and two colour difference signals which get processed to provide the colour information?

@Thread

The problem with the video chips in modern TVs is not due to the fact they are made in non-PAL countries, the problem is the Amiga.

The PAL non-interlaced video is not correct, there is a lack of equalising pulses which some TVs get upset with. I need to measure the interlaced output to see if that is correct.

If your TV has got RGB mode selection and aspect ratio control, you can leave these signals unconnected. I like them set as it save fiddling around with the remote. I will always recommend reducing the CSYNC signal to reduce the potential for damage to the TV.

23 pin connectors are difficult to obtain. I stocked up when Maplin finished with them

In the UK, ESR components sell 23 way plugs:
http://www.esr.co.uk/electronics/pro..._multipole.htm

Hopefully over christmas I will have some free time to play with video circuits.

Ian

[Dreamcast270mhz]

y Pr pb, they have the proper cables on ebay

[orange]

a question about shield, ("pin 21") should it be connected on both ends?

[orange]

ok, I connected the blanikng and got the picture. thanks

btw, I found this interesting link:
http://mts.speccy.cz/doc/128_rgb.pdf

its used for connecting ZX spectrum+3 to RGB scart, so it has interesting technical details.


i also so a solution for amstradCPC that connects SYNC to BLANKING to switch to RGB; what do you think about that? (unfotunately amstrad connector has neither +5 nor +12V; bit offtopic.. sorry..)

oh, and last question; can I connect R(G)(B) ground to blanking ground? (don't have enough wires..)

[Allen1]

=orange;641494]ok, I connected the blanikng and got the picture. thanks

btw, I found this interesting link:
http://mts.speccy.cz/doc/128_rgb.pdf

its used for connecting ZX spectrum+3 to RGB scart, so it has interesting technical details.


i also so a solution for amstradCPC that connects SYNC to BLANKING to switch to RGB; what do you think about that? (unfotunately amstrad connector has neither +5 nor +12V; bit offtopic.. sorry..)

oh, and last question; can I connect R(G)(B) ground to blanking ground? (don't have enough wires..)

Great link Mate,

I am tempted to get my +3 out but after all this time the chances of the disk drive belt surviving is very slim.

If you are talking about the Amiga then at the scart end all the grounds can be linked together and they are required to work properly with the RGB connections etc, on the Amiga side they share a common GND so no problem as long as it is just the GND's you share in the scart connector..

[Stedy]

Hello,

Not posted here for a while.

@Dreamcast270MHz

This thread has something underway that should interest you:
http://eab.abime.net/showthread.php?t=49874

@orange

When it comes to shielding I either have fully shielded 360 degree screening with metalised/shielded connectors or none at all. EMC 101, break the shielding anywhere, at least once and it is useless, the noise pickup increases by a factor of 10.

So in summary, I don't bother with SCART cables as the backsheel of the SCART lead is not shielded.

The ZX Spectrum +3 RGB mod looks reasonable, liked the explantion in the back of the document. Can't see a reason why it will not work.

[orange]

Originally Posted by Allen1

Great link Mate,

I am tempted to get my +3 out but after all this time the chances of the disk drive belt surviving is very slim.

If you are talking about the Amiga then at the scart end all the grounds can be linked together and they are required to work properly with the RGB connections etc, on the Amiga side they share a common GND so no problem as long as it is just the GND's you share in the scart connector..

hm, yes, but are you sure? because I noticed the blanking ground goes to LOGIC ground and there is 250 ohms between it and video GND on my A1200 (if I measured it correctly)

about +3, it takes 15min to change the belt, I do it without completely dismantling the drive. of course, finding the new belt is another story.

[Allen1]

Originally Posted by orange

hm, yes, but are you sure? because I noticed the blanking ground goes to LOGIC ground and there is 250 ohms between it and video GND on my A1200 (if I measured it correctly)

about +3, it takes 15min to change the belt, I do it without completely dismantling the drive. of course, finding the new belt is another story.

Hi there orange,

which pin are you meaning? pin 16 is Blanking Signal ( RGB Selection) and pin 18 is Blanking ground in the scart plug. Note that pin 16 in the scart is fed via a resistor from pin 23 at the Amiga end.

I have eventually found the information that I used to make my leads from and they all work with my 1200, 600.500 plus and 500.


I did change a belt on someone else's +3 about 7 years ago and getting a belt back then was pretty hard, I haven't got my speccy out yet as I have been doing other stuff, but one day I will

Good luck with your cable

[orange]

um, can i connect SCART pins 18 and 9 together, so that only one wire is used for all?

[Allen1]

Originally Posted by orange

um, can i connect SCART pins 18 and 9 together, so that only one wire is used for all?

In short the answer is Yes

On the scart end you could use 1 wire to connect to pins 4, 5, 9, 13, 14 and 18 together, I didn't use the shield pin 21. Better to use more than just 1 wire if you can though!

[Rocs9005]

Hi

Thanks for all these posts, very useful info here.

I just got a Amiga RGB to Scart cable, and it doesn't seem to work very well. Lets start with the good.
It does autoselect RGB Scart input on the TV.
The sound works.
It does show a picture
However, the picture is very unstable, especially towards the top of the screen.

I got out my multimeter, and checked the connections, and it seems to be very differently wired up that the info in this (and other similar) threads.

None of the video grounds on the scart end (5,9,13) appear to be connected to any pin on the amiga end.
The Audio Ground (Scart 4) is also not connected to anything

Scart 18 (Logic ground), is on Amiga 19 (Ground)
Scart 17 (Comp Vid Ground) is on Amiga 17
Scart 17 is also connected to the phono plug grounds.

I understand (especially from the last very helpful post) that all the grounds are common and internally connected on the Amiga end, and therefore am not worried if a Scart ground is connected to the "wrong" Amiga ground, but surely the Scart end video grounds need to be connected to something!?! I haven't got a good way to find out if the all the SCART grounds are all connected together TV side, But I suppose I could plug a SCART-SCART lead in and try measuring with that.

Also,

Scart 20 is connected to Amiga 10, but with no resistance.
Scart 8 (switch) is connected to Amiga 22 but with no resistance.
Scart 16 is connected to Amiga 23, with 177 Ohms measured.

If I understand right, the switch one is not vital, but could the lack of a ~330 ohm resistor bewtween Scart 20 and Amiga 10 be what is causing the unstable picture? Or is it more likely to be the lack of grounds at the scart end?

Thanks in advance for any advice.

Rocs9005

[Allen1]

Whoever sold you that cable has done a pretty poor job, its a case of link up all the GNDs and add the other resistors in the scart connector. I know the cables I use from alexh's description work and if I had paid good money for a half hearted attempt of a cable like the one you got I would be furious.

[Rocs9005]

Hi

I'm not furious (especially as he's offered me a full refund, so I'll only be down the return postage) but I have to say I was disappointed. I knew it was a risk, as I've read many posts of people having trouble with these cables, but I was pretty shocked at quite how differently the cable was wired from the generally accepted "correct" way for an Amiga.

Seller says it works for him and the wiring of Stedys one didnt work on any of his TVs etc. Not sure I believe that, but I'll keep my mouth shut until I find one that works for me.

The bad news is sending the cable back means I can't try adding that 330 Ohm resistor to see if that would have solved it.

The good news is that I found my old 23pin to 9pin monitor cable (from my very first Amiga monitor which died years ago) so am going to buy a normal scart-scart cable, and make up my own from those 2. Already got the resistors as I went near a maplins today.

My run of Amiga based bad luck continues, but there's hope yet!

Rocs9005