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Vic20 and C64 on same monitor possible? (1802)


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Anybody know if I can have both computer on the same monitor using this cable for the Vic20?

Maybe by using the from RCA connector.




I also have a 1084 monitor connected to an Amiga 500.



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Kind of. The 1802 has three sets of inputs:

  • Chroma + luma + mono audio. This is the best signal you can get from a C64, except the very first ones
  • Composite video + mono audio. This is what you'd use on the VIC-20.
  • Monochrome (green IIRC) video. This mode shares audio with one of the other two inputs.

The cable you link to has composite video + stereo sound, which is a bit of a waste since even on TV's with stereo inputs, they automatically switch to mono audio mode if only the left (or is it right? I never remember) plug is connected.


Since the 1802 only has one each of the video inputs, it means if you get two of the same cable, one of them will only display in B&W which is what happens if you feed a composite video signal as luminance and leave the chrominance unconnected. I would recommend you to try to get one 5-pin composite video cable, and one 8-pin chroma + luma (also known as S-video) cable for the C64.


You could also use the 1084, as it has switchable input for composite or chroma + luma, and your Amiga probably already uses the third, RGB input.

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Looks like they know what they are talking about. The VIC and C64 are not stereo, so I assume the left and right audio are just bridged.


The VIC and early C64 have 5-pin video out and are composite only- there is no separate Y/C, so the video quality will not be as good as a newer C64 with that capability and the correct chroma/luma separated cable.

With that said, this cable should work with either the VIC or any C64, it's just not the best option for newer (1983 and later) C64's.

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Thank you all.


I already have the S-Video for the C64. Actually I have 2.


So can I have the (C64 chroma+sound) and the (Vic20 composite + sound) on the switch and keep the red from the C64 in the monitor?


Since I have a spear cable. anybody knows if an 8-pin to 5-pin Din adapter exist?

I only saw 5 to mini-6 and connectors.

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Actually you can have both cables fully attached to the monitor. No need for an external composite video switcher as long as you don't need more than the mentioned systems, and you're using the 1802 which has these inputs. I doubt you could connect chroma directly to the 1802 and then feed luminance through a composite video switcher that is connected to the composite video input anyway, since that would be splitting the two signals onto two different inputs.


I used to have both a C64 (S-Video), a VIC-20 (composite video) and sometimes an Amiga 500 (green monochrome!) on the same 1802 monitor in the late 1990's, before the monitor begun to malfunction. The fact that when I opened it up, I lost my grip and broke the motherboard in two didn't help its functionality... :-(


An adapter cable would mean a male 5-pin to female 262 degree (uncommon!) 8-pin, rerouting pin 4 (composite video) to pin 1 (luminance). The reason you need the 8-pin female connector is of course to have all the pins to fit on the existing cable. I have never seen a such adapter, but it would be possible to build if one is very motivated. As a bonus, it would actually allow one to use a composite video cable intended for a Sega Genesis 1 & other systems, on a VIC-20, C64, Atari 8-bit etc since it is the composite video on pin 4 vs pin 1 that differs. However it seems quite a bit far fetched, and if you're going to solder, you could as well build a 5-pin composite video cable directly instead of making a custom adapter to use a S-Video cable as composite video.

Edited by carlsson
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Yup. Actually when you mention front and rear is this yet another example of how Commodore sold several different monitors under the same common model name. The front/rear reminds me more about 1702 than 1802, but I'm sure there are 1802 monitors with this configuration too. I'm too lazy to look up that monitor page I linked to elsewhere a few days ago, but it would suggest your monitor has 2, rather than 3 inputs as I discussed above.

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I think it will be easier to use the 1084 monitor.

If I'm not mistaking the switch for TTL-RGB/Composite is in the front, right?

I'm not sure if CVBS=TTL-RGB.


Or is it the switch next to the composite input in the back?


I think my Amiga is connected to the TTL-RGB input.


See image below.


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I would have thought your Amiga is connected to the blocked linear RGB socket between the TTL and SCART inputs. The fact that your monitor has SCART makes me wonder if it is a PAL model, despite your Canadian location? It is true that the Amiga outputs both analog and TTL level signals, but I think you get far less colours using TTL.


The switch on the front toggles between the RCA connectors and the different RGB options, whether you're using TTL or SCART. Actually I would think there is another switch between TTL and analog, but perhaps only the later 1084D models have that switch.


The switch on the back side toggles between composite video / CVBS (yellow only) and S-Video / LCA (yellow + red) whereas the white is for mono audio.


If the SCART connector indeed is operational, it would have inputs for composite video and possibly analog RGB too. Due to the fact that the 21 pin SCART connector is filled with useless pins according to an old standard, they had to reuse some of the RGB input pins to support S-Video on some devices, meaning that normally one outlet can't support both RGB and S-Video. Devices having two SCART connectors have these pins wired differently to maximize use, and sometimes can be configured in hardware or onscreen menus if you want to use the second SCART with RGB or S-Video. That however doesn't apply to the 1084.


Also, if your monitor is PAL but your VIC and C64 are NTSC, you will get a B&W image anyway.

Edited by carlsson
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Looks like the picture I took from the web is a PAL like you mention.


I just checked my connection and it's on the second RGB, the one on the right. The SCART is not available.


Anyway, I ordered the cable, it should be here soon since its ships from Canada.


I will update this post in to report on the different options in case somebody have the same questions.


Thank you for all the help, very appreciated.

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  • 2 weeks later...

Just a quick update.


I received the cable today.

post-25394-0-40617900-1485390446_thumb.jpg post-25394-0-17789300-1485390464_thumb.jpg



Connected it to the 1802 monitor. The one with my C64 connected to it.

To select the input you have to use the Signal Selection switch located at the back on the monitor.

As you can see below in my setup, the only way to get there is to pull out the monitor from the shelf.

But it's working perfectly ... with all the colors!

post-25394-0-08380300-1485390807_thumb.jpg post-25394-0-90600900-1485390823_thumb.jpg


I also tried with the 1084, the one that I use for the Amiga 500.

The Amiga is connected to the RGB.

I've connected the yellow RCA cable in the back.

The push button next to the RCA button needs to be in the CVBS position.


It's also working great and the color are even better and It's a lot easier to use the push button in from of the monitor to go from one to the other!

So I will use the 1084.




Thank you all again for the help.


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While I'm late to the party, this may be useful for somebody who finds this topic in the future.


In the past (reply #7) I used Composite to S-Video adapters to connect a couple of my composite only systems via an S-Video switch box to my C= 1084S.


The VIC 20 looked great:



Though the Nomad (Genesis) ended up with vertical banding:






Since then I've picked up a C= 1084 (non-S) and have all my composite only systems hooked up to it:


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I have a 4 way s-video/composite switch with 2 monitor output. (from Conrad Bestell-Nr.: 1435388 - 62 ) I have a breakout cable from the switch (s-video > chroma-luma) to the monitor and a 5-PIN DIN for VIC20 and 8-PIN DIN for C64. Both computers are connected, and the display is switched at the push of a button.

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