Thank you for participating in the Slingbox Answers Forum. I see, you're having problems with your Slingbox getting a black screen no matter what channel you have.
Now, the more details and information you can provide, the better we (the forum community and Sling Media) can help.
What Slingbox model do you have?
What cables are you using?
How do you have the equipment set?
Sling Media Support