How''s your VIC display?

[ral-clan]

Okay great. But I wonder then, if the pots inside the video section of the VIC (that we all have tweaked to get our monitor displays to be nice and bright) will still work.

[eslapion]

Can you guys be just a little bit patient please?

I know a solution with op-amps is more complex and takes more time than cutting the traces but please don't do that.

A simple small daughterboard under the video chip with a single chip dual op-amp will give you the best of both worlds...

[ral-clan]

Sounds good.

[gklinger]

Can you guys be just a little bit patient please?

I know a solution with op-amps is more complex and takes more time than cutting the traces but please don't do that.

Why not?

A simple small daughterboard under the video chip with a single chip dual op-amp will give you the best of both worlds...

I assume this will be free like a4000bear's hack so please tell us where we can get them. Thanks.

[eslapion]

Can you guys be just a little bit patient please?

I know a solution with op-amps is more complex and takes more time than cutting the traces but please don't do that.

Why not?

Because this will destroy the built-in composite output of the vic-20 main board. Good luck getting it back at any time in the future.

A simple small daughterboard under the video chip with a single chip dual op-amp will give you the best of both worlds...

I assume this will be free like a4000bear's hack so please tell us where we can get them. Thanks.

I can give you a plan for free.

All this involves is putting a daughterboard between the videochip and the VIC's main board. This board would connect pins 2 and 3 to a simple low cost high speed op-amp that will boost the output signal coming from the video chip and this way, you can have the s-video out without destroying the standard output.

I think the TLC072 is good enough to do the job. That's a 2$ chip.

A4000bear's solution works but it is not free. It too implies a few electronic components.

I think its a good idea to invest a few more dollars then to destroy a part of your VIC's main board.

I think its a very good idea to tap into the separate signals coming from the video chip to get a better display, but I am not butchering my VIC to save on a 2$ chip.

[eslapion]

[gklinger]

Because this will destroy the built-in composite output of the vic-20 main board. Good luck getting it back at any time in the future.

A4000bear warned us about that and as I don't need composite video, I don't care. Is there anything else to be concerned about?

I can give you a plan for free.

Now you're talking. Please post the plans here, if possible.

I'm curious how the S-video be delivered? It would be tremendous if the video out jack could be replaced with an 8-pin DIN like the one used on the 64 that could produce both composite and split L/C. That's a mod I would pay good money to have done to my VIC.

[eslapion]

Because this will destroy the built-in composite output of the vic-20 main board. Good luck getting it back at any time in the future.

A4000bear warned us about that and as I don't need composite video, I don't care. Is there anything else to be concerned about?

Of course. If you make a mistake, you could altogether ruin your board.

I can give you a plan for free.

Now you're talking. Please post the plans here, if possible.

Please understand I am very much overworked with the Behr Bonz presently. But I can assure you, this kind of plan is extremely simple.

It involves using an op-amp in its simplest configuration, the voltage follower:

I'm curious how the S-video be delivered? It would be tremendous if the video out jack could be replaced with an 8-pin DIN like the one used on the 64 that could produce both composite and split L/C. That's a mod I would pay good money to have done to my VIC.

If you use a small daughterboard under the video chip, the s-video signal comes from a small connector attached to that board.

If you want an 8 pin female DIN connector like that of the 64 to provide both the s-video and composite video, there's nothing to prevent you from putting on that board the same parts that are on the VIC's MoBo to remodulate together the luma and chroma signals and create a new composite signal.

However, if you want a complete 8 pin DIN connector, you'll also have to do the same for audio.

This board could have up to 20 components on it but all of them would be very simple parts like transistors, the sole dual channel op-amp, resistors and small capacitors.

[a4000bear]

Looks like I have created quite a debate here!

Of course, I have the luxury of owning two VICs, so modifying one is not a real problem.

Of course it is possible to do my mod without cutting PCB tracks...but the result is rather messy looking in that one would need a S-video cable hanging out the back of the VIC, rather than using the inbuilt connector.

The modification I have done makes very little visible change to the component side of the PCB.

The VIC chip is designed to drive a standard video load directly. The resistor and capacitor are there to provide the correct colour level of 0.3V at the colour burst into a standard 75 ohm load. It duplicates the existing ones used for the luminance (ex composite) signal.

One thing I will say is that once you have seen the quality of the S-video signal, you will NEVER willingly go back to composite!

Over the weekend I will document this for you with before and after pics.

[eslapion]

Of course it is possible to do my mod without cutting PCB tracks...but the result is rather messy looking in that one would need a S-video cable hanging out the back of the VIC, rather than using the inbuilt connector.

My first idea was to get such a cable out the datasette port.

However, after gklinger's suggestion, I think it would be possible to mod a VIC to remove the 5 pin DIN connector and replace it with an 8 pin connector and get the same output configuration as a Commodore 64 with both the composite and separate video signals coming out a single (standard?) jack.

I assume your configuration creates a non standard pinout on the original 5 pin DIN connector.

The VIC chip is designed to drive a standard video load directly. The resistor and capacitor are there to provide the correct colour level of 0.3V at the colour burst into a standard 75 ohm load. It duplicates the existing ones used for the luminance (ex composite) signal.

Would you have a simple schematics of what you have done?

My idea with the low voltage, high speed dual op-amp was to duplicate the signals coming from the VIC chip so that it can drive two different loads if needed.

One thing I will say is that once you have seen the quality of the S-video signal, you will NEVER willingly go back to composite!

My own VIC is very often used to demo things and on video equipment that's not mine.

If I am to make this modification to my VIC, I would certainly want to make sure I keep what's needed for "outside" compatibility.

Having the same type of connection as the C64 seems to bring the best of both worlds with s-video for the home and composite when needed. That is most likely the type of alteration I would want to do to my own VIC.

[a4000bear]

My first idea was to get such a cable out the datasette port.

However, after gklinger's suggestion, I think it would be possible to mod a VIC to remove the 5 pin DIN connector and replace it with an 8 pin connector and get the same output configuration as a Commodore 64 with both the composite and separate video signals coming out a single (standard?) jack.

I assume your configuration creates a non standard pinout on the original 5 pin DIN connector.

That is correct. There are two pins connected together on the original DIN connector. I isolate one of them with a track cut and put the C signal on it. I can't remember what signal is on those two pins, I'll be checking tomorrow, when I document the modification.

Would you have a simple schematics of what you have done?

I will be making up a schematic tomorrow.

My idea with the low voltage, high speed dual op-amp was to duplicate the signals coming from the VIC chip so that it can drive two different loads if needed.

Yes, I assumed that is your intent. You might like to use a MAX496 or MAX497 chip. They are specially designed for video, contain 4 amplifiers in the one package, and only need a single 5V supply. I have used them in a video switcher I designed, They are a very good chip and easily obtainable.

My own VIC is very often used to demo things and on video equipment that's not mine.

If I am to make this modification to my VIC, I would certainly want to make sure I keep what's needed for "outside" compatibility.

Having the same type of connection as the C64 seems to bring the best of both worlds with s-video for the home and composite when needed. That is most likely the type of alteration I would want to do to my own VIC.

One easy way to achieve a composite output from a S-Video only source is to get an S-video to composite adaptor, They are cheap, easily obtainable, require no power and do a good job. Otherwise you could make your own.

[gklinger]

One easy way to achieve a composite output from a S-Video only source is to get an S-video to composite adaptor, They are cheap, easily obtainable, require no power and do a good job. Otherwise you could make your own.

That's what I was thinking. I've been putting it off for a while now but I've long had a plan to make an all-in-one video cable from a 64 style 8-pin DIN to composite, luma, chroma, S-video as well as two mono audio so that I can connect to whatever monitor or TV I encounter. Shouldn't be too difficult to make. Even I could do it.

Such a cable would work nicely with a VIC-20 that was modded to use an 8-pin DIN with all the pins configured like a 64...

[eslapion]

My idea with the low voltage, high speed dual op-amp was to duplicate the signals coming from the VIC chip so that it can drive two different loads if needed.

Yes, I assumed that is your intent. You might like to use a MAX496 or MAX497 chip. They are specially designed for video, contain 4 amplifiers in the one package, and only need a single 5V supply. I have used them in a video switcher I designed, They are a very good chip and easily obtainable.

Maxim semiconductor says: This part remains available but is not recommended for new designs.

But I have to say, considering the application, it does have much better specs than the TLC072 which can also work with a single 5V supply.

Added edit:
Neither Digikey nor Mouser carries that chip... easily obtainable??

[eslapion]

One easy way to achieve a composite output from a S-Video only source is to get an S-video to composite adaptor, They are cheap, easily obtainable, require no power and do a good job. Otherwise you could make your own.

Such a cable would work nicely with a VIC-20 that was modded to use an 8-pin DIN with all the pins configured like a 64...

If you had a VIC that was modded to have the same pinout on an 8 pin DIN, you wouldn't even need that cable.

The 64 has both s-video and composite out from the 8 pin DIN conector.

[gklinger]

The 64 has both s-video and composite out from the 8 pin DIN conector.

Yeah, that's my point exactly. I was referring to a cable that had five RCA plugs (composite, luma, chroma and two mono audio) and a singles tandard 4-pin S-video plug. Plug it into a 64, or a modded VIC-20, and into a monitor with composite in, split L/C delivered over RCA (like many C= monitors) or a TV with an S-video input.

The reason I'm so gung-ho about this is that I was sick of relying on old monitors that were prone to failure so I bought a Toshiba 20AF46C and two Toshiba 14AF46C CRT televisions to use exclusively with my Commodores. I use the composite input for my VIC-20, the S-video input for my 64 and the component input for my Amiga and the display quality is fantastic. My dream is to be able to connect my VIC-20 to the S-video input so that its display will be as nice as the 64s.