S-Video conversion possible as plug-and-play solution?

[tokra]

A thought just crossed my mind recently: Is it possible to do the S-Video conversion as a plug-and-play solution? I had own VIC-20s modded by some friendly fellas a few years back, but I think most users still have to live with the poor composite video-output of their VICs.

My idea would be to pull the VIC-chip out of the socket, and put a board (or just an IC-socket?) in between that consists of the necessary parts for S-Video-output and has an S-video-cable with a plug on the end that you could just let hang out of the user-port for example.

Is this idea even technically doable?

[eslapion]

My quick and dirty solution to the S-Video mod requires that you have a VIC-20 with the 656X on a socket.

I bent outward the Chroma pin and placed the chip back in its socket to allow the luma to follow its normal course and be buffered normally, making the normal video output monochrome.

Then I soldered a 360 Ohms resistor and 0.1uF surface mount capacitor in series to the bent chroma pin. Open up an S-Video Cable, solder the luma line to the DIN 5 video out, solder the chroma line to the added components.

Et voilà!

[mrr19121970]

Sounds sweet, but I am not sure I'd be willing to risk killing a machine to do this.

Perhaps you can upload some photos for us to see too? Questions:

Did you not need to cut the trace bewteen output 4&5
Why not put the capacitor and resistor in the s-video cable?
Why not us a connector on the chip leg (instead of soldering)
Why does this example us a 70ohm resistor? the 'usual' s-video fix uses 300ohm (like you)
Why is the capactior needed?

[eslapion]

The Commodore 64 was one of the very first consumer device to offer separate Luma and Chroma signals to improve resolution.

As such, it offered its own level of amplitude and DC offset for chroma. The luma+sync is equivalent to a standard monochrome TV signal. The early 1701/1702/1084 monitors were configured for these values and could directly be attached to the C64/C128 separate video signal. The VIC-20 internally generates luma+sync and chroma at the same electrical levels as the C64/C128 but it didn't offer a non-mixed output.

The S-Video norm appeared later with the advent of S-VHS and other high quality home video devices such as lazerdiscs, etc... The luma+sync remains the same but the chroma signal has a much lower amplitude and no DC offset.

The capacitor resolves the different DC offset and the resistor reduces the amplitude to match that of standard S-Video.

Disconnecting the chroma pin of the video chip from the board turns the outgoing composite signal into a normal luma+sync.

Did you not need to cut the trace bewteen output 4&5

Since I tap the chroma directly from the video chip, why on earth would I do something like that?

Why does this example us a 70ohm resistor? the 'usual' s-video fix uses 300ohm (like you)

Probably because since it sends the chroma to pin 5, which you don't need when you tap it directly on the video chip, it is likely adjusted for a Commodore monitor.

[ken]

I did a very simple hack and added 1 on/off switch to add svideo
so the vic20 has composite and flip the switch it now has svideo
even made a real nice 5 pin composite/svideo cable
I have posted picks somewhere about doing it

[RobertBe]

...solution to the S-Video mod requires that you have a VIC-20 with the 656X on a socket.

I bent outward the Chroma pin and placed the chip back in its socket to allow the luma to follow its normal course and be buffered normally, making the normal video output monochrome.

Then I soldered a 360 Ohms resistor and 0.1uF surface mount capacitor in series to the bent chroma pin. Open up an S-Video Cable, solder the luma line to the DIN 5 video out, solder the chroma line to the added components.

Using Eslapion's above solution as a starting point, Ray Carlsen just modded my main NTSC VIC-20 for s-video! This is what Ray wrote --

"I... go one step further and change the A/V connector to the 8 pin version robbed off a duff C64 board. Of course the VIC20 board must be pulled to access its underside.

Snip the top 3 pins so the connector will fit back in the board. Drill a hole in the metal cage to pass the chroma line through and solder the chroma line to pin 6 on the back side of the connector.

Switching the chroma out of the luminance [is] done by tying the lines to the two unused pins of the new A/V socket.

(snip)

The A/V connector can now be used for five (composite) or eight (S-video) pin plugs. With a Commodore 3 wire cable plugged in, the output is S-video to the monitor. With a five pin plug for composite, the user must install a jumper in the upper two pins of the A/V connector. I made one out of a large paper clip, just a thick U shaped jumper that easy to remove if you want to do S-video. That eliminates the need for a separate switch.

The only downside is the loss of +5V for the RF adapter. Voltage for that adapter comes out on A/V pin 1 of the VIC20. That pin is used for the luminance signal S connection with an 8 Pin plug of a C64 or 128. I cut the +5VDC line to pin 1 and connected pin 1 to pin 4 so those pins now provide video output to both 5 and 8 pin connectors.

The bottom line: the S output looks great.

[Off-topic]

It just occurred to me that the first C64 board (#326298) also has a five pin DIN and would be even easier to convert to 8 pin S-video. It already has a high-res luminance output on pin 1 just like the later boards. The only thing it doesn't have is the chroma output. Swapping the connectors and providing chroma on pin 6 will upgrade it."

Truly,
Robert Bernardo
Fresno Commodore User Group
http://www.dickestel.com/fcug.htm

[eslapion]

@RobertBe
Nice

I didn't consider the alteration possible on the 326298. Good idea.

[Muzz73]

Nice!

I am going to send Ray a few wonky C=64 boards soon, so I may just send him my spare VIC-20CR board and have him do this as well.

This is so cool! Thanks for posting this!

[mrr19121970]

@RobertBe

Will you please also post pics?

[RobertBe]

Ray sent me a photo. I can get it posted tomorrow.

Truly,
Robert Bernardo
Fresno Commodore User Group
http://www.dickestel.com/fcug.htm

[RobertBe]

Heh, the image link isn't working for me. I'll try it another way.

Truly,
Robert Bernardo
Fresno Commodore User Group
http://www.dickestel.com/fcug.htm

[RobertBe]

O.K., I put Ray's photo of the conversion at

http://blog.retro-link.com/2016/03/vic- ... video.html

Truly,
Robert Bernardo
Fresno Commodore User Group
http://www.dickestel.com/fcug.htm

[mrr19121970]

It looks nice, but not really 'plug and play'. I imagined that Ray would have managed a 'daughter board' type of setup, were you unplug the VIC-I and drop in the daughter board and the VIC-I. The daughter board would have all the needed components to deliver straight to a croma, lumina, audio jack that you could have dangling out of your case.

[RobertBe]

The daughter board would have all the needed components to deliver straight to a croma, lumina, audio jack that you could have dangling out of your case.

Straight from Ray -

"I'm always thinking of the final product, something anyone can use once the mod is installed. For example, if you wanted your VIC20 modded, you wouldn't want wires dangling out the back."

Truly,
Robert Bernardo
Fresno Commodore User Group
http://www.dickestel.com/fcug.htm

[mrr19121970]

That's only an opion, and I have a differing one. Doesn't make mine or Ray's wrong just as they are different?

Let's humour the idea further? Would it be possible? What would be needed?

Shopping list
1 x Pack of test probes http://www.ebay.com/itm/121901525743
1 x 330ohm resistor
1 x 0.1uF ceramic cap
1 x precision socket (snip off pin 2 - better still. Insulate with heatshrink???)
1 x s-video jack *
2 x rca jack (or 3.5mm headphone socket) *
* or rca stereo plug and s-video cable directly
1 x bits of wire
1 x some shrink wrap

Recipe for octopus cable
A. VIC-I PIN2-> Hook -> 330 ohm resistor + 0,1uF ceramic cap -> s-video chroma (shrink wrapped for insulation)
B. Video Out PIN5 -> Hook -> s-video luma/sync
C. Video Out PIN3 -> Hook -> audio left & audio right
D. Any GND -> Hook -> s-video ground 1&2 + audio left+right ground

Recipe for plug and play
Remove VIC-I from socket, insert into new socket with PIN2 removed. Connect Hook A. Insert back onto mainboard
Connect Hook B, C and D
Enjoy s-video using standard cable and audio jacks or black and white only composite using original video output.

VIC-1 Pinout


Video Out Pinout