Fairchild channel F question from a listener

[SubaruBrat]

Hi, I was wondering if you knew how to troubleshoot a channel f that has everything working but the video? I have sound and the select buttons work along with the controllers and the cartridge slot. You may be thinking how do i know if I have no video? I have another working console that I can compare it to and I can hear the sounds respond to button and controller movements. Even if you can't explain it because it's to complex, could you point me in the right direction? Maybe someone that can repair it for a reasonable price? Thanks in advance. Basaione

This is a fairly simple thing to troubleshoot but you do need to know how to read a schematic and it would be best to have some electronics gear, a multimeter and an Oscope. The video is generated in the graphics processor and then modulated in the RF unit (turned into a TV signal). The way I would go about this is to determine if the GPU or RF unit was bad to cut the problem in half. If you look at the first sheet of the schematic you will see that the RF section has a video input and an output, the input comes from the GPU (pin 10 of the GPU) and the output is the connector going to your TV. By checking the signal at that pin you know if the RF section is getting an input. If no signal is present the GPU is probably bad, although supporting circuitry could be at fault. If a signal is present then some failure has occurred in the RF modulator.

Now obviously if your asking this question you probably don't know much about schematics and likely don't own an Oscope, and I hate to give advice that isn't of much practical use. And realistically while the RF components are easily found the GPU isn't unless you salvage one from another Channel F. The best solution for you is to probably find a working Channel F missing all the extras (cheaper) and swap the PCB into your unit. If you want to take this on as an opportunity to learn a bit about electronics you are in a good position having two units. You can buy a cheap PC based Oscope or an older analog Textronics unit on ebay (cheap) and you will have a working example Channel F to compare signals with. If you follow the trace on the PCB from pin 10 of the GPU you can literally trace your way though the RF section and see the signal being modulated and disappear at the failed component.

[teknohed]

I'd be curious to see this up and running. I've always wanted a Channel F myself. It's fairly primitive hardware which means that it would hopefully be fairly straight forward to fix.