S-Video modding a composite only CRT.


Twinkle Star Sprite
Hey all, I got my hands on a new old stock DWT1905 TV, which was something really cool to find. It came in its factory box all sealed, pristine condition, great geometry (and rounded which I prefer to flat CRTs).

The TV is composite and RF only, but I got it with the intention of doing an RGB mod or getting a universal chassis and swapping that in, but before I do that I'd really like to try to get S-video out of it since the IC supports it.

I can't find a datasheet for the M61271M8-058FP chip that this TV uses, but I did find other TVs that use it and so I got an idea of which pins do what, and I found that pins 29 and 30 are for the luma and chroma input. Wiring directly to these gets me an svideo signal but the colors are distorted and there's some warping of the image.

I tried some circuits suggested here and a couple other places, and I cant get that problem to go away. Here's the diagram for the chip from another TVs service manual:


I've tried adding the components that the diagram shows, but it hasn't changed. I don't know too much about electronics so there's a chance I'm wiring it in wrong, that 10uf50v cap uses a symbol I'm not familiar with, so I tried wiring in series with the negative towards and away from the chip, neither worked.

Also my Saturn displays perfectly on this when I just wire the connection directly to the pins without any capacitors or resistors, everything else has issues, though, so I dont know how or why that's happening. I appreciate any help and advice, thanks.


Twinkle Star Sprite
Well, it's embarrassing but I fixed the issue. Turns out the circuit was correct and worked, but I had accidentally bridged the two pins together on the tiny IC. I couldn't even see the bridge, but a simple continuity test was all it took. A lot of careful re-soldering later, and everything works and looks great.