Power, But No Picture!
I encountered an odd problem with my Sega Genesis. Normally, when I turn the system on, even if there is no cartridge inside the system, the screen turns from blue to black. It doesn't do that anymore; it stays blue, and there is no change at all. I tried using different adapters, but that didn't work. I tried switching TV's, but that didn't work. So, I bought another one off Ebay, and I have the same problem on both TV's. The Genesis came with new adapters, except a Genesis power adapter, so I used another one. The new genesis came with a broken RF adapter [It won't fit the slot], and a Composite adapter that fits. The only thing that I had to re-use was the power adapter. What could be the problem? The red LED on the genesis turns on when I press the power button, so I don't think power is a problem.
Video Game Consoles & Games - Sega - Genesis Console
Answers & Comments
Try moving the a/v or rf cable in the back of the genesis
I encountered a similar problem a few years ago. The television that I was using did not have a coaxial (cable) line, so I had to us an adapter I have purchased at walmart to change the R/F adapter to RCA style A/V. Turned out that the problem was that this was bad.
So, My guess (given that you have used two televisions, and two different SEGA Genesis consoles) that thr problem would have to be something between the two that they would have in common.
My only other possible solution, would be that maybe the A/C adapter is functioning, but not properly. You could test it with a digital multimeter to make sure, or replace it with a universal A/C adapter, and adjust the voltage to 12 volts.