Simplest S-Video mod

[eslapion]

The original S-Video mod published by A4000bear was obviously designed for VIC-20s which have the 6560/61 soldered on the board.

Since none of my VIC-20s suffer this problem, I had a much easier solution. Lift pin 2 of the VIC-I from the socket, solder a 0.1uF capacitor to it in series with a 360 ohms resistor. There is your chroma signal.

Since you've now effectively turned your VIC-20 monochrome on the normal video port, you take the luma+sync signal from there.

If you don't understand by sifting through the text above, don't worry, I won't react with inflammatory comments. I'll just post a photo and that will save everyone a few thousands of words.

I'm kinda visual myself.

[lance.ewing]

One of these days, hopefully not too far away, I want to continue with my project to play around with the 6561 on a breadboard. I actually already have the 6561 on the breadboard, and various other 7400 series chips. I'm still in the process of laying it out though. The plan is certainly to use s-video, so whatever the easiest way is to do that, I'm all for giving it a try.

[mrr19121970]

As I mentioned in my previous post. I made this mod for a mate of mine. The cost being 'nothing' as all the bits are lying around in my box of parts. Remember ESD precautions. This is good for people who don't want to bend a leg or risk damaging the VIC-I with the soldering iron.

Parts list:

1x 40 PIN socket (snip leg off).

1x IC grabber
1x 26awg wire (10cm)
1x 0,1uF (104) ceramic cap (bend the legs 90 degrees and shorten)
1x 360 ohm resistor (shorten the legs)
1x ardiuno 1p dupont jumper (male-female), snipped in middle equal lengths. Use female, mail is for s-video cable.

1x 5cm heat shrink
1x ziptye (nylon cable binder)

Instructions:

1) Remove socketed VIC-I push in the socket with snipped leg. Push socket with snipped leg and VIC-I onto mainboard
2) solder all components in series
3) slide heatshrink over components just soldered and shrink
4) connect IC grabber to PIN2 of VIC-I

Allow male dupont connector to dangle out of the datasette port. Secure to the mainboard here (usually there is a drill hole unused at the datasette) with a ziptye.

The cable can be any type you can imagine. You can even take an eBay 5PIN -> Composite and a parallel chroma (1p dupont->RCA) for a 1084S.

[tokra]

I'm not an electrician, so most what you discuss here is lost on me. However I agree that nowadays most people will want to hook up their VIC to a modern flat-screen LCD-TV. So the WIKI should mention that the values are meant for Commodore Chroma/Luma-monitors and possibly which values would most likely work for modern TVs. Can you edit the WIKI to that fact?

That being said, S-Video inputs itself are becoming rare. I have a TV from 2013 that barely has S-Video input (only on Scart). A lot of recent TVs do not have S-Video-inputs at all. Even Composite is being phased out and soon there will likely only be TVs with HDMI. As long as converter-boxes are available that is not too big a problem, but even those will need inputs to handle S-Video.

[Kakemoms]

One has to consider that no two Vic-20'ies are the same with respect to analog output. They may be somewhat within specifications on the digital aspect, but with respect to a given voltage I have never seen a Vic-20 that actually has the specified voltage. Fluctuations on analog signals (as the composite video) is all over and having an adjustable pot to get an external converter to lock, is quite interesting.

[eslapion]

One has to consider that no two Vic-20'ies are the same with respect to analog output.

When VICs came out of the factory, they were extremely well adjusted.

Of course, all electronic components age and change characteristics (especially capacitors) and most VIC-20s need readjusting nowadays. However, components which are more than 20 years old have very little characteristics drift and a VIC-20 which is properly adjusted today will likely stay within correct signal range for the next 15 years or more.

All VIC-20s now are more than 30 years old. My own PSK VIC is 35 years old.

having an adjustable pot to get an external converter to lock, is quite interesting

It may be interesting but you don't know whether you're getting the signal correct or within tolerances for the specific converter or compensating for another inadequate setting.

[Kakemoms]

One has to consider that no two Vic-20'ies are the same with respect to analog output.

When VICs came out of the factory, they were extremely well adjusted.

Of course, all electronic components age and change characteristics (especially capacitors) and most VIC-20s need readjusting nowadays. However, components which are more than 20 years old have very little characteristics drift and a VIC-20 which is properly adjusted today will likely stay within correct signal range for the next 15 years or more.

All VIC-20s now are more than 30 years old. My own PSK VIC is 35 years old.

having an adjustable pot to get an external converter to lock, is quite interesting

It may be interesting but you don't know whether you're getting the signal correct or within tolerances for the specific converter or compensating for another inadequate setting.

Yes I know.. sigh.. we are all drifting into old age. I doubt we can be tuned back to youngsters. At least I take my antioxidants and jog each week.

We should have an anti-age-guide for the Vic.

[groepaz]

if we look at the big brother of the vic-20 ....the c64

...then we can observe that they were not quite extremely well adjusted at all (did you know they hired housewifes to do the final assembly/adjustment/testing...). i dare to assume the vic20 wasn't any better (chances are that it was even worse).

and indeed, adjusting chroma/luma with a pot until the picture is good is no problem at all (and indeed, the level is too high for a lot of modern displays). its not much different to what you would do with the knobs on your tv/monitor anyway. just keep in mind that this pot is there and you might have to re-adjust when using another display

[eslapion]

if we look at the big brother of the vic-20 ....the c64

...then we can observe that they were not quite extremely well adjusted at all (did you know they hired housewifes to do the final assembly/adjustment/testing...). i dare to assume the vic20 wasn't any better (chances are that it was even worse).

and indeed, adjusting chroma/luma with a pot until the picture is good is no problem at all (and indeed, the level is too high for a lot of modern displays). its not much different to what you would do with the knobs on your tv/monitor anyway. just keep in mind that this pot is there and you might have to re-adjust when using another display

You have a few scope captures from the 1980s to back this up ?

You do know the FCC in the US was hot on the trail of Colecovision and Commodore computers and looking for any reasons to blame them (and Atari 2600 machines) for poor TV reception in rural areas ?

A poorly adjusted modulator (they are built-in on the C64) could generate noise on multiple TV channels.

There were even amateur radio operators blaming early home computers and gaming consoles for interfering with their activity.

Added edit:
I was a teenager in the years I first owned and used a VIC-20 so obviously I know only about the situation in north america for that era.

[groepaz]

A poorly adjusted modulator (they are built-in on the C64) could generate noise on multiple TV channels.

yup. it's also completely unrelated to the luma/chroma levels - what are you trying to say?

[eslapion]

A poorly adjusted modulator (they are built-in on the C64) could generate noise on multiple TV channels.

yup. it's also completely unrelated to the luma/chroma levels - what are you trying to say?

You said (about the C64)...

...then we can observe that they were not quite extremely well adjusted at all (did you know they hired housewifes to do the final assembly/adjustment/testing...).

Well it so happens in the C64 the luma/chroma level adjustments are in the modulator.

If you fool around with the adjustments on the modulator, you may succeed in getting a very nice display for yourself but you can end up messing with the TV reception of your neighbors.

Also, I can assure you the settings of the C64 modulator, which includes luma/chroma levels were top notch when you got it brand new for the above reason.

[joshuadenmark]

If you don't understand by sifting through the text above, don't worry, I won't react with inflammatory comments. I'll just post a photo and that will save everyone a few thousands of words.

I'm kinda visual myself.

Yes please

[groepaz]

Well it so happens in the C64 the luma/chroma level adjustments are in the modulator.

sure, however you can tweak them however you like without affecting the channel or the sidebands or whatever else would potentially be a problem for your neighbours. in the first place you will get a bad picture when the level is too high.

[eslapion]

Well it so happens in the C64 the luma/chroma level adjustments are in the modulator.

sure, however you can tweak them however you like without affecting the channel or the sidebands or whatever else would potentially be a problem for your neighbours. in the first place you will get a bad picture when the level is too high.

1. I know for a fact this is completely false. C64 modulators are cheap and when they receive excessive levels of luma, sync or chroma they broadcast junk all over the spectrum.

2. People who start tweaking in their modulators because they want to improve their display usually don't know which adjustment is related to the luma or chroma level and they play with pretty much everything they can tweak including the variable coils - my point remains, C64 modulators were adjusted to near perfection when they came out of the shop and if they had not, the FCC would have been all over Commodore.

3. What exactly does this have to do with VIC-20 S-Video mod and doing it the right way ? - IMHO you just want to argue for the sake of arguing to simply steer the exchange away from the main issue; making a VIC-20 S-Video mod begins with getting your VIC-20 adjusted correctly first and THEN modding. Getting a picture that "looks" right absolutely doesn't mean your signal is ok.

Yes please

At your service...

There are 3 attachment points in the image above.
1. The white wire is the easiest connection to the ground I could solder - the nearest point was too tight for the soldering iron to get in and many other places had no thermal relief so that's the best compromise I could find

2. The luma+sync is connected to the output of the video amplifier with LC filter

3. The chroma is attached directly to pin 2 of the 6560 via a 360 Ohms resistor in series with a 1206 SMT capacitor of 0.1 uF.

[groepaz]

I know for a fact this is completely false. C64 modulators are cheap and when they receive excessive levels of luma, sync or chroma they broadcast junk all over the spectrum.

and long before they will do that the picture will be complete shit - so why would anyone do it?