Commodore 64 8-pin video connector. Is there +5V or not?

[oracle_jedi]

Hoping someone knows this and has a quick answer, otherwise I am going to have to pull the 64s out of the closet and rig up a test.

 

 

I've seen at least 4 different pin outs of the C64's 8-pin din video connector.  

 

A +5V supply is shown variously on pins 8, 7, 5 and not at all.

 

I know very early 64s had the 5-pin connector.  Not talking about those.  Strictly regarding the 8-pin variety - is there a +5V supply and if so, where is it?

 

 

 

 

 

 

[+OLD CS1]

A good question.  The schematics for 250649, 250425, 250466, and 240441 show 5V at pin 8, while 250407-04 show N/C for pin 8.  I did not look any further.  Soooo, if these schematics match reality, then some models have 5V at pin 8, some do not.

 

Reference: https://www.zimmers.net/anonftp/pub/cbm/schematics/computers/c64/

 

I would say that if you need 5V for an external device, get it from the cassette port like myriad components from the era do.

[hofster]

Beware that the pinout images you get if you do a web search have different pin numbering patterns. That's likely why you see contradictory information on which pin number is which signal.

[carlsson]

I wonder if this was a leftover from the 5-pin DIN connector on the VIC-20 which has 6V (or perhaps it is 5V) at maximum 10 mA intended to drive the RF modulator. Since the C64 has the modulator built-in, eventually perhaps they figured out there was no reason to route a voltage through the A/V port any longer.

[hofster]

I don't think so. 5V is on one of the top pins that don't exist on the 5 pin connector.

[hofster]

5 minutes ago, hofster said:

I don't think so. 5V is on one of the top pins that don't exist on the 5 pin connector.

Well, the general idea might well be a leftover from the VIC-20.

[oracle_jedi]

7 hours ago, OLD CS1 said:

A good question.  The schematics for 250649, 250425, 250466, and 240441 show 5V at pin 8, while 250407-04 show N/C for pin 8.  I did not look any further.  Soooo, if these schematics match reality, then some models have 5V at pin 8, some do not.

 

Reference: https://www.zimmers.net/anonftp/pub/cbm/schematics/computers/c64/

 

I would say that if you need 5V for an external device, get it from the cassette port like myriad components from the era do.

 

Thanks for sharing that.

 

I am trying to replicate the work of @puppetmark and create a simple s-video/luma to RGB adapter, using an LM1881, so I get some more use out of my Atari SC1224 monitor.  I got a first version done, but I wanted to improve it by using an 8-pin din connector that works for both Atari 8-bits and Commodore 64/Plus4 machines.  If the Commodore has +5V on pin 8 then it wont need an external +5V which would be convenient.

 

I checked one of my C64s though and no +5V on pin 8

 

 

 

 

Edited May 13 by oracle_jedi

[+OLD CS1]

6 minutes ago, oracle_jedi said:

I checked one of my C64s though and no +5V on pin 8

If you are doing this just for yourself, it should not be a big deal to attach 5V to pin 8, provided it is N/C in your system.  If you are doing it for a wider range of users, then a lot of us would have no problems with doing the same.  Not as convenient as a single, all-in-one module, for sure, but still worth the effort for some.

[+mytek]

On 5/12/2024 at 7:14 PM, oracle_jedi said:

 

Thanks for sharing that.

 

I am trying to replicate the work of @puppetmark and create a simple s-video/luma to RGB adapter, using an LM1881, so I get some more use out of my Atari SC1224 monitor.  I got a first version done, but I wanted to improve it by using an 8-pin din connector that works for both Atari 8-bits and Commodore 64/Plus4 machines.  If the Commodore has +5V on pin 8 then it wont need an external +5V which would be convenient.

 

I checked one of my C64s though and no +5V on pin 8

 

 

 

 

I'm curious how you will be doing this, since I too have an SC1224 collecting dust.

[oracle_jedi]

The current state of the Gerber with some pictures and examples is shown here:

 

 

I plan to make some more changes through.  Right now I think I need an extra 150 ohm resistor on the LED, as they keep blowing.  I might also switch to a USB-C connector for power, versus the 2-pin Dupont connector I use now.

 

@mytek  - definitely interested to know if you have an opinion on this!

  

 

[+mytek]

28 minutes ago, oracle_jedi said:

The current state of the Gerber with some pictures and examples is shown here:

 

 

I plan to make some more changes through.  Right now I think I need an extra 150 ohm resistor on the LED, as they keep blowing.  I might also switch to a USB-C connector for power, versus the 2-pin Dupont connector I use now.

 

@mytek  - definitely interested to know if you have an opinion on this!

  

 

 

Thank you for the quick response. I'll have some time Monday night to look this over, and I'll try to get back to on Tuesday to let you know what I think or if I come up with a suggestion that might make it better.

[+mytek]

@oracle_jedi I checked out that linked page and downloaded the gerbers to take a look at it in a viewer.

 

I'm a bit confused here since you mentioned something about an LED and S-Video, but I see no indication of either in the PCB. So it must be something that you are presently working on, and the gerbers for that are not available.

 

 

As I read a bit more, it appears that you aren't actually converting either composite or S-Video to RGB, but instead are just using it in a monochrome mode. Having an LM1881 Sync Separator to get your independent V and H signals that the SC1224 requires, and then feeding the luma into one of the RGB lines. Still monochrome, but with the choice of which color you wish to use.

 

So my wishes got dashed, since I was really hoping that this was a true S-Video to RGB conversion suitable for either the Atari or C64. As it stands I already have a Chinese converter (somewhere??) that does this, Although it is a bit flickery, so I was hoping for a better solution.

 

EDIT: Aww I see the LED in the picture, but it looks like an after thought. if it's being fed via the 75 ohm resistor, that definitely is too small if the source is 5V. I would start at 1K and see what you get brightness-wise. Some LEDs require a high drive (usually older ones) and in the past I've found 390 ohms works pretty good for those, whereas the newer high efficiency types sometimes require 3K in order not to blind you.

[oracle_jedi]

Correct, this PCB is only designed to allow composite and SVideo to be displayed on the SC1224 in monochrome.

 

For colour, I have used this:

 

https://www.amazon.com/dp/B0B1TJWCXC?psc=1&ref=ppx_yo2ov_dt_b_product_details

 

 

These are designed as an add-on to the OSSC, but can also operate independently.   It takes Composite or SVideo and converts it to RGBS over SCART, component RGB or YPBPR.    It works with PAL, NTSC and SECAM.

 

At around $100, these are not cheap, but so far I am impressed with the results.  No noticeable lag or jitter, even on full-screen scrolling games like Dropzone.

 

Below is a pic of my PAL Plus/4 outputting to my North American 1084 over the RGB input.

 

 

Combining this with the LM1881 PCB design, I can get composite or SVideo output to display in colour on the SC1224.

 

 

 

[+mytek]

I came across a couple of early Sophia boards that I had gotten years ago which output RGB and separate sync directly from the GTIA chip piggyback. I had forgotten all about these.

 

This really is the best way to interface my SC2224 for extra crispy and noise-free graphics plus text from an A8. However it doesn't do much for the C64 situation   Although there's the Kawari or LumaCode solutions for HDMI that work really well.

 

Thanks for the info on your project, and I hope it does all that you need it to.