Component Video mod for curved screen Sony Trinitrons

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roboblaster
Posts: 10
Joined: Sat Nov 09, 2024 11:04 am

Re: Component Video mod for curved screen Sony Trinitrons

Post by roboblaster »

I recently picked up an XF34M31 set that uses BG3S chassis. This is a later model than BG3R that I normally look for, and on this one they have removed the component input. I think it might have been a cheaper model.
Anyway, I added RGB SCART, but now I also want to add back the component input to use with PS2.
From reading up in this thread I think it should be possible but I could use some help interpreting the service manual.

Tracing back the jungle inputs (36-39), it goes back to a header CN303. This looks like a good place to inject the signal.

My understanding is that I need coupling caps in the path and terminate the signals with 75 ohm to ground. Looking at the diagram there and highlighted pins:

https://imgur.com/qc5VQ31

RY: Coupling cap in circuit. Seems to be grounded via R312 (470 ohms? should R312 be removed?). It's also connected to Q302/Q303 matrix transistors (?? what's that about ??)
BY: Coupling cap in circuit. Not sure what diode to ground does, i assume it still needs termination with 75 ohm?
Y: Coupling cap in circuit, no grounding. The Y input will be split to go to jungle input and svideo luma so it shouldnt need termination?
YS: Havent figured out what voltage this needs to be yet, will have to check chip data sheet later

anyone able to help me decipher this to speed things up a bit? :)
Bard_the_Bowman
Posts: 37
Joined: Mon Apr 29, 2024 5:42 am

Re: Component Video mod for curved screen Sony Trinitrons

Post by Bard_the_Bowman »

matt wrote: Fri Jun 21, 2024 10:16 pm
Bard_the_Bowman wrote: Tue Jun 18, 2024 7:32 pmHey Matt, I tried going with this approach and I'm now getting a terrible interference/hum out of the right audio channel. Do you have any thoughts on what might be causing that or how I might reduce it?
Usually this is a grounding issue.
Turns out I was being really dumb. I have the horizontal switch shift wired into my 6P3T toggle, but at the time of that post I'd stuffed up the wiring. I had one of the wires for the horizontal shift switch going to a post that was supposed to be for one of the left audio wires, and vice versa. (used white wires for both and evidently got sloppy). So yeah, was probably sending voltage right into the audio circuit which unsurprisingly caused an unpleasant noise lol.

So, I guess the lesson is if you're doing this mod with a many-poled switch, just be VERY meticulous with your wiring.
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