S-Video from the VIC

[Mayhem]

I can only think the cable might have been designed for early issue C64s (that have five pin video out) then, and Dimitri discovered it worked perfectly well for the Vic20. Certainly I wouldn't be able to get a picture out of my Vic-1001 without it as it's NTSC and I'm in PAL land, and the RF wouldn't cough up a jot.

And yes, there is a little distortion on the image, but the picture overall is more than fine.

[SparkyNZ]

The Commodore 64 has S-video out already, but the Vic doesn't, so no, that cable won't work.
Yes, there's different Vic motherboards, so you need to adapt the mod to your particular version. Using the schematics in first post in this thread, it's pretty easy to adapt the mod for your particular version of motherboard if you know a little of electronics. I did that and posted it here:

http://sleepingelephant.com/ipw-web/bul ... php?t=3721

OK, I'm going to give the cable a go for my C64C.. and once I get a bit more info an clarification on the Vic20 S-Video mod for my board I'll give that a go.. Unfortunately I need to buy a small LCD TV with s-video since the kids broke my s-video module on my plasma.. I just hope I can get a cheap enough TV with NTSC support (my plasma supports both PAL & NTSC and we're in PAL land in NZ).

[Mike]

And yes, there is a little distortion on the image, but the picture overall is more than fine.

You could always compare with my program 'Colour Test' (link).

Here's a detail before ... [...] ... and after the S-Video mod: [...]

Note the jagged edges in the top picture. I took these pictures when I modded tokra's VIC-20. The difference is even more apparent with the checkerboard pattern, but one of the picture shots turned out too blurred for a good comparison.

The picture quality of my VIC-20 had been even worse before the mod, see here: (link).

[SparkyNZ]

Note the jagged edges in the top picture. I took these pictures when I modded tokra's VIC-20. The difference is even more apparent with the checkerboard pattern, but one of the picture shots turned out too blurred for a good comparison.

Mine looks exactly like the top picture with the composite connector.. so you can see why I want to make the mod.

[rhurst]

I always find an s-video mod discussion interesting... proper pot tweaking of the VIC chip and using a quality composite cable and LCD monitor never gave me any lust to molest original working parts.

See my link here and you can't convince me that it is not good enough. I understand the 'jagged' color noise VIC produces, but that's also what we grew up with... if it bothers you that much, use xvic. Or a modern machine with more than 8-colors.

BTW, don't take this the wrong way... love the electronic hacking, and Mike's "color" test program. Modding makes me nervous, which is my shortcoming.

[SparkyNZ]

I always find an s-video mod discussion interesting... proper pot tweaking of the VIC chip and using a quality composite cable and LCD monitor never gave me any lust to molest original working parts.

See my link here and you can't convince me that it is not good enough. I understand the 'jagged' color noise VIC produces, but that's also what we grew up with... if it bothers you that much, use xvic. Or a modern machine with more than 8-colors.

BTW, don't take this the wrong way... love the electronic hacking, and Mike's "color" test program. Modding makes me nervous, which is my shortcoming.

That HP monitor you bought obviously does a great job. They're pretty expensive in NZ. I'm not wanting to spend a lot of cash on improving my display so I just want to get the S-video working so I can use the Vic on a cheap small LCD TV (same story with my C64). You're right - I grew up with jagged edges on my Vic using a portable TV via the RF modulator but after using XVic.exe, of course I have been spoiled with the display on my laptop etc.

Still.. I have 2 Vics and I would like to use the real thing and experience the "wow" and "inner glow" factor of seeing a sharper display from one of my Vics. Most people think I'm nuts for wanting a Vic20 in the first place

[Mike]

I understand the 'jagged' color noise VIC produces, but that's also what we grew up with...

Now I am going to tell you something. Even in those early days, I had been annoyed by these cross-hatch patterns. Only at that time, I did not know (yet) what could be done about that.

On a PAL VIC-20, these patterns don't flicker at a 30 Hz rate (as on NTSC), rather they are rock-steady. Depending on which pair of VIC-20/TV or monitor is used, the effect can reduce letters with certain colour combinations to an unreadable pulp.

When I had modded my VIC-20 to display VFLI images, the composite signal was now *the* quality limiting factor!

if it bothers you that much, use xvic. Or a modern machine with more than 8-colors.

Or do something about it on the original hardware.

[rhurst]

... because YOU can!!

Luckily, I can just spend $$.

[SparkyNZ]

Hi Everyone

I managed to get my S-video mod working on my old 324002-01 Rev F board.

Here's the result:



I have a lot of ghosting on the screen.. The above characters seem to half a purple/pink haze to the left of them and are darker to the right. Its most noticable for the red 'HELLO' text. This would suggest to me that perhaps the chroma is not in phase with the luminance.. perhaps??

Does anyone have any idea how I can resolve this.. I feel like I'm nearly there.. Maybe its something that I can adjust on my TV itself (I'll have to have a look at the TV).

Here's how I did my mod - same as the others on here.. just seperating the Vic 6560 pin 2 from the rest of the board (I pulled the chip out of the socket first) and then feeding pin 2 into the capacitor and resistor combination. See pic below which I knocked up. I cheated in that I used an SVideo-to-SVideo cable and cut one end off and put a 5pin DIN on the other end.



If anyone has a solution for the ghosting/phase problem, I'd really appreciate it. I don't know if any of the pots within the Vic chip area or not would help at all?

[rhurst]

Have you adjusted the VIC pot to increase (signal strength?), because your white looks too dark (gray) in this picture. Maybe that will get help rid of the darker ghosting evident with the colored characters.

[Mike]

Newer TVs do a heavy amount of preprocessing before the video signal is put to display.

I suppose your LCD tries to compensate for known deficiencies of PAL and NTSC, where older TVs normally would take some 150 nanoseconds time to recognize the colour phase (i.e. hue) has changed, thus leaking the hue into the *right* neighbor pixel.

You could try to deactivate image 'enhancements', if that is available in the menu of your LCD. And compare how the display appears on an older CRT.

In an older thread, 'Gaps between characters on video output', another LCD had similar problems, albeit this time with the composite signal (sadly the screen pics are defunct now).

Edit:

I managed to get my S-video mod working on my old 324002-01 Rev F board.

If you take a look at the schematics in the thread 'S-Video mod on PCB model 324002-02 rev D', you see a LC filter applied to pin 4, maybe it is similar on your board revision. This could also incur a significant delay on the (remaining) luma signal. What result do you get, when you connect your luma to pin 5 of the video connector instead?

I read 120 pF and 3.9 µH. This would correspond to a transition frequency of ~7.4 MHz.

[eslapion]

@SparkyNZ:
I can see by the slight polka dot pattern on your display that your chroma signal is a bit too strong.

[SparkyNZ]

Have you adjusted the VIC pot to increase (signal strength?), because your white looks too dark (gray) in this picture. Maybe that will get help rid of the darker ghosting evident with the colored characters.

Its just the camera on my iPod thats making it look as dark. The actual colours on the screen are fantastic... just shifted a bit to the left thats all.

[SparkyNZ]

I suppose your LCD tries to compensate for known deficiencies of PAL and NTSC, where older TVs normally would take some 150 nanoseconds time to recognize the colour phase (i.e. hue) has changed, thus leaking the hue into the *right* neighbor pixel.

My C64C doesn't do this with S-video (is that because its more modern than the Vic and doesn't have the 150ns delay?)

Unfortunately I can't find anything I can tweak on the S-video settings for the TV so I can't try turning any features off.

If you take a look at the schematics in the thread 'S-Video mod on PCB model 324002-02 rev D', you see a LC filter applied to pin 4, maybe it is similar on your board revision. This could also incur a significant delay on the (remaining) luma signal. What result do you get, when you connect your luma to pin 5 of the video connector instead?

I haven't tried pin 5 of the video connector - I thought this was "AUDIO IN" but just had a look at the 'E' schematic and I see that indeed its connected to the video circuit. I can give that a try..

I hear what you're saying about trying it on an old CRT etc. Unfortunately practically nobody that I know still has one - in fact its becoming hard enough now finding an LCD that still has S-video these days in NZ.

[SparkyNZ]

@SparkyNZ:
I can see by the slight polka dot pattern on your display that your chroma signal is a bit too strong.

I'm not too worried about that.. If I can get the phase sorted out I'd be keen to fix it though. What would I need to trim that down. Would a bigger (variable) resistor in my PIN2 chain do the job?