Brilliant picture from Amiga with RGB-SCART

I wanted to be able to hook up an Amiga 500 to TV with decent picture quality for an upcoming gaming session. Instead of using the lousy composhite signal or the dreadful RF antenna cable I wanted something much better because modern TVs don’t forgive low-quality video signal. In fact, flat panel TVs tend to make old systems look really bad. Low resolution and sharp, pixelled graphics (in contrary to e.g. real life video) transferred using blurry and noisy signal, and then displayed stretched and processed on a HD panel. You know it ain’t gonna be pretty! The best way to prevent the worst eyesores is to use high quality video signal at least.

So, off to make a RGB SCART cable for that Amiga.

The most convincing diagram I found for such cable was at Ian Stedman’s site. Instead of blindly building wirings using diagrams found off Internet I like to cross reference things. After having a look at Amiga RGB port’s pinout one of the connections in Stedman’s diagram was starting to look suspicious.

Amiga RGB pin 13 to SCART pin 18

According to NT Rautanen’s pinout information on the Amiga RGB port pin 13 is “Ground Return for External Clock Enable”. Connecting that to blanking signal ground did not seem logical to me. Additionally, NT Rautanen’s page specifically says  that do not connect pin 13 with pins 16-20 (video ground) on the Amiga RGB port.

As it turns out Stedman’s diagram is likely to do just that. It is likely that most TVs and monitors with SCART socket have all the ground lines at SCART socket connected. I backed up this assumption with the TVs in our household using a continuity meter. In other words connecting Amiga RGB port pin 13 to any SCART ground connects it with the common ground (including the pins 16-20 in Amiga RGB port).

Other than that, Stedman’s diagram looked good, including all the control signals and some resistors to adjust the voltage levels.

I built my cable according to Stedman’s diagram, except for the above mentioned A13-S18 line. I also used the suggested 220 ohm resistor instead of the 75 ohms in the blanking / RGB mode selection signal (SCART pin 16).

Here is Stedman’s diagram with the modification I did for my cable:

The cable I had and used for this was 8-wire shielded data cable. Six wires was needed for the signals, so two wires and the shielding copper web was left for the ground. I connected all the relevant ground pins making use of the remaining wires and the shielding. The more ground pins connected the better, I think.

Left: The Amiga end of the cable in the making. RGB signal wires and resistors soldered in.
Right: Cable ends ready for test.

I measured the voltage levels on the control and sync signals when the cable was connected to TV, and they were well in the specified range.

  • SCART pin 8, status & aspect ratio: 11,5 V, telling the TV to switch to this AV input in 4:3 aspect ratio.
  • SCART pin 16, blanking signal & RGB-mode: 1,2 V, telling the TV to use RGB signal.
  • SCART pin 20, composite video/sync: average voltage level of 0,6 V

The Amiga RGB port does not provide audio, so the cable needs additional RCA plugs for left and right channels, which can be found at the back of the Amiga. I used some leftover AV cable which I cut and soldered to the SCART plug and ran alongside the video cable.

The cable works fine, and on both TVs I tested it the picture quality is very good (Samsung LCD, Panasonic plasma). The TVs accept the signals without problem, and both TVs switch to AV mode and displays the picture in correct mode and ratio without touching any settings. The picture is very sharp and quite stable. There is only very slight vertical wobbling in the picture, but we are talking about a magnitude of 1/10th of effective (signal) pixel at most. On Panasonic considerably less than on Samsung. It’s possible that using a cable better suited for analog signal would eliminate this slight defect.

Left: Finished cable.
Right: Cable connected to Amiga – excuse me for not having the lid on!

Ok, I was happy, but vintage machines on a modern HD TV just does not look “right”. I dug out my Philips CM 8833 monitor and had a go with that. To my disappointment the picture was missing the red component. I wouldn’t be taking that so I started investigating. I double-checked with completely different system and RGB cable and clearly the fault was not in the cable but in the monitor. I opened the monitor casing hoping that I would find a clear discontinuity in the red signal line, hopefully near the SCART plug. I had to dismantle the monitor internals quite a bit before I got access to the underside of the circuit board where the SCART plug was soldered to. A word of warning: CRT tubes use very high voltages. There’s a risk of serious electric shock if you stick your finger to a wrong spot.

And as it turned out, the fault was obvious. Many of the SCART plug’s connections were broken off from the PCB. I simply heated up the connector legs one by one and applied some fresh resin.

Put everything back together and tried again. Brilliant picture I tell you!

The tube does not scale or process anything, it now displays the video signal in its rawest, purest form. Although low resolution, the picture is sharp! The picture consists of lines of light, not of blocky pixels. The lovely scanlines are there. Just like it should be. It’s perfect!

Now some pictures I took for comparison.

All these photos are directly from the camera without any further processing – so they are quite big. Taking pictures from TV is a bit tricky. I did my best to avoid scan stripes on the CRT. On flat panel TVs there are some moiré on the pictures. Of course you can’t see either of these effects on a plain eye. These pictures are provided only to give an idea of the differences. The best pictures to compare are the Turrican stage photos.

First off some pictures taken from the Philips CM8833 monitor using composite signal. The signal is generated by the external A520 video module.

And then similar pictures from the same monitor, but using the RGB SCART cable.

Now pictures taken from low-end Samsung LCD TV (the model is LE23R86BC if you’re interested of such details) using the RGB cable.

And finally, pictures taken from Panasonic plasma-TV (TX-P42G20E), again using the RGB SCART. The second Turrican stage picture is taken using a zoom mode on the TV, so that the picture fills most of the screen area.

24 Responses to Brilliant picture from Amiga with RGB-SCART

  1. Walter says:

    Hi, don’t know how old this is as there are no dates, but here goes anyway…

    I’m going crazy trying to connect these correctly. Here’s the background…

    I live in south America, Argentina, where our TVs are a crazy PAL-N, but at least they also have the american NTSC formats. Our TVs also don’t have the european SCART connector, only RF, composite, and on the newer ones component and HDMI (plus VGA on the LCDs)

    I bought several computers in the UK, which are of course PAL, but PAL-B? (or maybe even PAL-I some of them??).

    In any case, when I hook them up to our TV of course it’s black and white.

    I was told I would either need a compatible TV, or a converter, or an RGB monitor.

    Now my doubt is the following…

    As I understood, when you connect these (Amiga, Atari, etc) through the RGB output, you’r basically outputting the raw signal, and at that point there’s no more PAL/NTSC anymore, is this correct?

    Regading SCART, that per my understanding is just the CONNECTOR type, isn’t it? If so, isn’t there a way I could make acable that maps the Amiga’s pins to a different connector and use that on my LCD/CRT tv/monitor???

    • ilesj says:

      Hi, yes, that is correct – the RGB signal is “raw” analog video signal carrying the red, green and blue signal components independently un-encoded. Thus RGB video signal is just that, there is no NTSC RGB or PAL RGB, just RGB. The refresh rates (50/60 Hz) can be different between regions though. The black and white picture is a result from incompatible colour information encoding (e.g. PAL/NTSC) between source and display.

      SCART is an old European standard for general use A/V connector, yes. And yes, you can map the signals to some other connector.

      Reading your description, I think you are left with VGA. However, you might need a so called “scan doubler” or some sort of converter, as the VGA inputs of modern monitors of TVs most likely will not accept the 15 kHz horizontal sync frequency of an Amiga. A 15kHz RGB to VGA converter would probably be useful for you. That said, I have no experience with them.

      EDIT: Alternatively you could try to source yourself an old video monitor, like that Philips CM8833. A display from same era as the machines is not a bad choise at all ;) Good luck!

  2. Walter says:

    Sorry, also, what-s the difference on the las 2 sets of pics when you mention the “RGB cable and the “RGB SCART cable”? I know the last one is the one you make in the article, but what is the former? What connect does it have? Thanks!

    • ilesj says:

      Ah, that’s just mixed use of terms from me. All but the first pictures (composite signal) are taken using the RGB SCART cable I made.

  3. A600 freak says:

    Nice, you’re being able to repair those SCART pins in the monitor. CRTs scare the sh*t outta me, I would not open these unless under serious other threat! :)

    Oh and congrats, amazing signal on the Panasonic plasma!

    • ilesj says:

      I can assure you I wore rubber gloves when I stuffed my hands into the “snake’s nest” of wires while taking the monitor internals apart :P

  4. Erik says:

    Hi Ilesj,
    I read your article with great interest and I was wondering if you know what causes the display to be off centre and not completely fill out the screen?

    I have the same set up, and my display is off centre, to the left. I don’t seem to have any option filling out the screen evenly. You seem to have the same issue as you mention using zoom, right?

    Regards,

    • ilesj says:

      Hi, I have the same thing going on – there are borders around the screen and the picture is slightly shifted.

      The borders are overscan area of sorts, as the resolution of Amiga picture is less than what even the traditional display specifications would allow. Amigas and other home computers were of course designed for CRT displays, and on those, part of the borders would extend outside of the visible screen. On a fully analog consumer video technology it was good to have some tolerance. Modern TVs will likely show the full or most of the signal area displaying the relatively thick borders. If possible, adjusting overscan setting or zooming the picture will compensate this.

      The shifting to left is another thing. I was wondering the same thing and found a likely explanation. It has to do with the horizontal sync signal, and it being slightly off compared to the RGB video signal. The composite video signal is slightly delayed compared to the RGB video signal due to encoding process. As the cable uses the composite signal for sync, the small delay between RGB and composite makes the picture shift left. The RGB signal is “ahead” of the sync signal. Or that’s how I’ve understood this. Someone please correct me if I’m wrong, or knows what could be done to fix this.

      Both of these ‘features’ are not a problem with e.g. that CM 8833 monitor. Both the picture width & height and horiontal position can be adjusted using analog dials. So basically the ‘problem’ is the era gap between the machine and display ;)

    • Erik says:

      Thanks!
      I found a way around it, namely just using my samsung tv (lcd monitor actually). It’s a fairly new monitor, definately modern (20″) but the display is as it should be; right in the middle.

      I haven’t really checked but the above seems to be pointing towards it having something to do with differences between plasma and lcd technology.

      Adjusting overscan prefs is something the people from Amiga kit also suggested (his case actually kind of disproves my lcde/plasma theory btw..):

      “Hi,

      This will be down to the TV shifting it to the left.
      I had same problem on my samsung LCD. If you have a workbench and whdload setup, I used overscan in prefs to get round the problem.”

  5. Alexander says:

    Thanks alot for this guide! But I got a issue, i’ve soldered it up and when I connect it, it switches to the right input but it pops up “no signal”. I also tried using just the composite (version), nothing.. But the Mono connection works but it shows me gray/white -ish. The issue is that i have some error on my A500 and i need the rgb connection to find out the “code”.

    • ilesj says:

      Do you know if the video out gives any video signal at all? If your machine powers up it probably gives the controls signals, and that makes the TV to switch to the AV input even if there is no video signal. AFAIK the monochrome video out of A500 is supposed to give B/W picture. Have you got the A520 external video module? If so, give that a try.

  6. benzi says:

    I dug out my A500 a few days ago to use on a Sony Trinitron I got off ebay a while back. The Trinitron works flawlessly on PS2/Xbox/C64/Spectrum all connected via RGB scart.

    To my disappointment the A500 colours do not display properly using the RGB scart lead I purchased off ebay years ago. The colour is kind of off and there are greenish bands on the boot screen (amiga V1.2 hand).

    Strange thing is when hooked up to my Panasonic Plasma the A500 via the scart lead colours are fine (although it looks blocky and disgusting as expected).

    Is it my scart lead or the TV? RGB is fine with other game consoles/computers and RF looks ok (fuzzy).

    Please help!

    • ilesj says:

      Can’t really tell, but my first suspect would be the SCART lead. If there is something fishy in the cable or signal, it could explain the different behavior on the two TVs. Check and rule out the possibility that neither the Sony or Panasonic are switching to composite. Usually SCART cables always carries the composite video signal as well. If there is something odd in the RGB signal, the TV might switch to composite instead.

      I suggest also trying a different, preferably a known good cable.

      But what I know for sure is that the C64 does not output RGB ;)

    • benzi says:

      Thanks for the reply. I forgot to add that when playing a game (interphase) the red face logo on the title screen sort of slowly pulsates, like the red is changing in intensity. Really strange. The Kickstart 1.3 boot screen looks like someone has pushed a speaker against my CRT.

      I want to try another lead but dont want to waste my dosh!

  7. Steve says:

    Hi
    I have followeed your guide to create my own rgb cable for my amiga 500. I have soldered every cable correctly as far as I now but when I connect the cable to the amiga and the scart to the TV and I switch on the computer I does not power on. I have to dissconect the scart cable from the TV and then swicht on the computer so that it powers on. What do you thing it could be?, very strange problem. I hope you understand my english.
    Thanks
    Bye!

    • ilesj says:

      Hi,
      Sounds like a short-circuit to me. Get yourself a continuity meter or a multimeter, and check each and every pin with all other pins. None of the lines/pins that are not supposed to be connected should not make any contact or reading. And obviously the cable must not be connected when testing this.

    • Steve says:

      Hi
      Thanks for answering. I have fixed it but now the problem is that the screen is very dark. I cannot see anything.
      Do you know what can this be?
      I have checked all the pins.
      Thanks
      Bye

  8. John says:

    Hello
    I connect pin 10 to the required resistor and 19 to a composite video cable to the tv but I’m only getting a black screen any idea what could be the problem?
    Thank you

    • ilesj says:

      If I understand correct you have connected the composite video cable to the Amiga video port, and connected the RCA plug into television composite input? That’s not right. The optional composite video connector is for acquiring alternative sync signal source for the RGB video, not for providing a composite video from the Amiga. Please refer to the original Ian Stedman’s article for explanation for the alternative sync source.

      I.e. the optional composite cable is SYNC SOURCE, not VIDEO OUTPUT. If the optional composite video connector is used, it has to be connected to the SCART plug, not to the Amiga connector.

      Obviously all the other lines in the diagram needs to be connected also for this RGB cable to work.

  9. […] I created a scart cable for my Amiga. I took the schematics from ilesj’s blog and for the first time I had a color picture on my TV. Not counting the GBS8200 experiment I did. […]

  10. Claus says:

    Hi ilesj
    I want to build that cable, but I dont understand you wrote you only connect 6 lines from the RGB port. If I calculate right you need more than 6 lines right ? Which pins are not connected ? You mention using a 8 lines data cable and using 2 lines+shield for gnd. Leave 6 lines back to connect at the RGB plug?
    The only way I can see that must be Sync TTL is not connected and Composite and all the video grounds using the same LINE. ?

    • ilesj says:

      Hi,
      I connect six signal lines:
      -Analog Red
      -Analog Green
      -Analog Blue
      -Composite Sync
      – +12V DC (control signal)
      – +5V DC (control signal)

      That leaves two unused wires in an 8-wire cable. I used both of them (plus the wire shielding mesh) for connecting the ground.

      All the analog ground lines are the one and same. At Amiga RGB port, pins 16-20 are the same, and are interconnected.

      So, you can connect the various (analog) ground pins to each other at the connector, and then just run at least one shared ground wire between the connectors. This applies also to the SCART plug.

      Left and right audio runs in a separate cable, please check the pictures (There’s two cables coming out from the SCART connector: the 8-wire cable for video and control signals, and normal stereo audio cable – there’s no audio in Amiga RGB port).

      IF you want to have also the audio in the same cable as the video, you need min. 9 wire cable. But then you need to route the audio to the cable at the Amiga end.

      I hope this clarifies!

  11. Walter says:

    Hi ilesj, quick question:

    What do you use/recomend for the cable? I don’t have a y store at my location that sells a cable with so many leads inside, and I can either get unipolar (they only have 5 colors…) or he suggested I just use a UTP cable… wouldn’t this last one be too thin? Or will the twisting cause any issue woth these specific signals?

    • ilesj says:

      Hi! Instead of twisted pair cable, I would recommend something more suited/meant for analog video and audio signals. One option would be to recycle some old cables. For example you could use a normal SCART cable, and replace the other end with Amiga connector.

      Another option could be to use an old VGA cable: cut the VGA plugs off and strip the cable. If it’s a good quality VGA cable (the thicker the better, generally) there’s probably couple of wires that have tinfoil or braided shielding around them. These should be used for the RGB signals, and if there’s more of them, for Sync also.

      In fact old SCART or VGA cable should be better choice than a generic data cable that I used.

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