Jonathan Katz wrote: It is generating a good composite video signal. The next step is to depress the BREAK key. The screen should clear and the display should contain something like "C/W/D/M?". If you get that far, be sure the "CAP LOCK" key is depressed and press C. You should then be on your way to starting BASIC in ROM. All of the prompts that follow can be responded to by pressing return. Bill S.

There are two issues here: the video output from your challenger could be improperly formed for the modulator you are using. I don't recall for sure if you are in 50hz PAL land, SECAM, or NTSC land, but there may be some expectations by some modulators as to the timing of the composite video signal you distribute to the circuit. I'm guessing if you are in the US since you mention channel 3 tht you have it set up okay. The other issue is what would you see on a monitor which is capable of displaying via a composite signal. What you have displayed looks like your processor is not running to clear and paint any reasonable contents into the video memory, and you are getting out well formed composite video of garbage from your video ram. I'd try to dig out an old style video monitor and check that. The second thing that might be happening if the video monitor is working, is that you might be killing your processor when you connect your lashup of Challenger -> modulator -> display. When that happens it might be bad grounds or worse killing off the Challenger. When you use a 300 ohm feed adapter, I think that floats the two outputs connected to the broadcast receiver input which receives and displays channel 3. When you use a 75 ohm adapter, you have ground and center conductor, which will common the grounds thru from your display possibly to your computer. Hope this stimulates some idea as to what might be fouled up. Jim On 5/17/2012 1:31 PM, Jonathan Katz wrote: