Commodore 1701 tarnished RCA connectors

[old_tv_nut]

Here's a comb filter card for computer video capture, but it doesn't have analog output.
https://www.youtube.com/watch?app=desktop&v=xSb_-Y_vn5E

[luRaichu]

I found the Phillips/NXP TDA9183 chip which seems to have everything you need on the same IC. Example circuit looks simple enough + there is a DIP version available so you can probably breadboard it.

[old_tv_nut]

Originally Posted by luRaichu

I found the Phillips/NXP TDA9183 chip which seems to have everything you need on the same IC. Example circuit looks simple enough + there is a DIP version available so you can probably breadboard it.

A switched capacitor delay line - trying to think if I ever saw that implementation, but yes, it has everything needed.

[Electronic M]

Originally Posted by luRaichu

Somewhat off topic, but it would be nice to have a box that would comb filter Composite into the separate Y/C components since this set has the usual notch filter for Composite in.
Especially for use with Raspberry Pi analog out since their chipsets don't allow split Y/C, only Composite.
I'm not sure if this kind of device already exists but there's gotta plenty of comb filter chips out there for newer set designs. Would be an easy and interesting project that's for sure

You could look for an S-VHS VCR or one of the VCR/DVD recorder combos with S-video output....The transport need not work if you're just using it as a comb filter.

[ARC Tech-109]

It seems to be that an ordinary home VCR with a comb filter only passes the input right thru to the output (EE mode) without going thru the comb filter at all regardless if its composite or S-Video. I'd actually be inclined to pull the 1-H delay line out and use it with the Pi making my own Y/C separator.

[vol.2]

Originally Posted by luRaichu

I found the Phillips/NXP TDA9183 chip which seems to have everything you need on the same IC. Example circuit looks simple enough + there is a DIP version available so you can probably breadboard it.

Fudoh weighed in on comb filters in 2012 on AVS, you might find this interesting
https://www.avsforum.com/posts/22243853/

So if you can find an Entech SVSI or CVSI-1 for cheap you're in business, or get a Pioneer DVD recorder and run things through it.

1701 can only be RBG modded via the neck board, and I'm not aware of any examples for such a project on that set on the webs.

There's some cheap Aliexpress neck board kits, but idk if they are trustworthy or what.

[luRaichu]

I don't wanna bother with RGB mods. I watched an Adrian's Digital Basement video on YouTube about the 1701/1702 and I remember him saying that the RGB levels used are over 0.7Vpp. So you'd need to get some transistors and amplify your RGB to what the neckboard uses.

[vol.2]

Originally Posted by luRaichu

I don't wanna bother with RGB mods. I watched an Adrian's Digital Basement video on YouTube about the 1701/1702 and I remember him saying that the RGB levels used are over 0.7Vpp. So you'd need to get some transistors and amplify your RGB to what the neckboard uses.

The neck board mod kits are made to do that; they are essentially simple RGB input stages that give you a wide range of control over the tube grids, but rely on the existing electronics for sync and deflection. Like I said, I've never used one, but they should work in theory.

I don't know off the top of my head what the RGB voltages are for a 1701, but they are always higher than NTSC levels at the neck board. Just glancing at a random schematic for one of my sets, the drives take 5.8V and the outputs take 7V. After they leave the outputs, the RGB signals get boosted up to some level of roughly ~200V.

Don't get me wrong, I'm not advocating for it. I would probably just keep it Luma Chroma as that is sufficient IMHO. The leap from composite video to s-video is far, far greater than the leap from s-video to RGB. As far as I'm concerned, most people can't tell the difference between the two when the TV is viewed from a normal viewing distance; you have to take close-up pics to see the difference.

I think the main reason to do RGB in most cases is that it's convenient if you have a whole ecosystem of stuff that's already wired up that way. And it is a little bit better, so (all other things being equal) there's no reason to not have it.