Composite Mod for RF Only CRT?

[chillian]

Hello,

I had been wanting to learn how to get into CRT modding for a while and started doing some research a while back. I finally decided to get started with a simple composite mod for my GE Spacemaker 09GP344 that currently only accepts RF input. Looking at the schematics for it's TA1268N ic, I believe I could add S-Video or RGB input in the future if I wanted but for now I'll stick with composite.


Currently, I have everything soldered straight to the jungle ic with pins 37 and 53 lifted from the board. When they were still connected, there was a lot of interference from the RF modulator. This works for the most part.


When I turn on the TV and then turn on a console, it takes it a few seconds to "find" the video signal. This wouldn't really be a problem normally, but in the middle of a game it will sometimes "lose" the video signal and go back to the default blue screen. Then it takes it a few seconds to "find" the video signal again. I've noticed it tends to do that when the screen fades to either black or white with some repeatable exceptions. For example, in Sega Rally for the Saturn, there are certain points in each track where it will lose connection.

Should I add a resistor or capacitor somewhere? Or is there something else I've botched? Thanks for any and all help, I've looked around everywhere with no luck on a solution.

[KPackratt2k]

Assuming this is the same chassis as the 13-inch RCAs that I've modded, you can flash the EEPROM chip to enable Composite Video and inject it (along with audio) to an unpopulated header.

https://sector.sunthar.com/guides/crt-r ... 13710.html

If that doesn't work or you don't have access to an EEPROM programmer, you can inject Composite video into the tuner circuit once removing a few components.

Basically by removing RI532, RI528, and CI525, it isolates the tuner circuit's CVBS output. Then into the center leg of TI21 we can insert composite here and, voila, every "channel" in TV tuner mode is now that composite input. Similarly you can input composite sync on its own here, and it works in RGB mode too. Without this extra amplification step I was unable to get sync working properly.

For audio, remove CV30 and inject your audio to the pad that leads to pin 53 of the jungle chip.

By modding it this way, you'll lose the RF tuner input. If maintaining both RF and Composite are important to you, I recommend doing the EEPROM method instead.

No need to worry about this being a hot chassis, as these later RCA/GE TVs use an isolated power supply.

[chillian]

Awesome! Thanks man! That website looks super helpful for what I'm doing. I don't really care if I lose the RF signal so I will forgo the EEPROM programming for now since I do not have a programmer. I will definitely look into that for the future though.

I did, however, mess up the TA1268N ic with all the re-soldering i was doing on it and pin 37 broke off. I tried a couple fixes but that leg seems too far gone for me to save. I ordered a replacement chip since those are pretty cheap and I'll replace it and see how it goes this time.

I appreciate the help!