Exclamation wrote:
Hello all - was hoping to get some help with a mod on a Sony aa-1a chassis. As far as I can tell the closed captioning chip is really the only place I could do the mod on this tv - which is good because I don’t care about having cc enabled, and I think I could just remove the chip entirely, or at least remove the rgb pins if the chip needs to stay for some reason, but I don’t think it does it’s own blanking, so I assume I can just remove it and then change the resistors and caps that are already on the rgb traces to the jungle ic with the correct values and use the grounds that are already there too - also, I don’t guess I would need a switch on the rgb lines in that case. Reasonable?
If that works ok, my real problems are that I am very much a novice - this will be the first time I’ve ever even really thought about circuit design, so I don’t know how to determine the correct values for the resistors and caps, if the cables I’ll be using having 75ohm resistors in them affects what needs to be on the board, and I’m not clear on how to handle blanking. I couldn’t find a data sheet for this jungle chip, so not sure if it just needs 5v from any random ass point I can find going to the ys pin, or if it takes less voltage - I think I’ve seen 3 or 3.3v mentioned for some ic. Also wondering if there’s any reason like menu functionality, component protection, or safety that I would need a switch on the blanking if I only ever plan to use rgb on this tv?
Here’s a pic of the schematic between the cc chip and the jungle chip, and if it makes any difference, the model of this tv is 32-xbr45. Thanks in advance for any help!
https://imgur.com/gallery/uNnfFtLThe closed caption chip RGB lines are the ones you want to hijack. Hopefully there are some jumpers on the lines that you can remove to isolate the CC chip so you can inject your 75 Ohm terminated RGB. Otherwise possibly remove R101, R102, R103, R104, R105, R106 and inject the RGB into the pads of R102, R104 and R106 that go to the IC301. If you're good with a soldering iron you could put 75R surface mounts in R101, R103, R105 to be your termination.
For blanking you might want to lift the leg of Diode D003 that connects to caption chip and inject 5V into it. Run the 5V through a single point switch if you ever want to turn it off.