You didn’t mention the model you are using. So here I suggest a general method used to reset digital converter box to default settings.
1. Turn on your converter box, go to the "Function" menu and then select "Factory Reset."
2. Enter your PIN number (created during the initial setup) when prompted. This will restore your converter box factory settings.
3. Select "Auto Scan" from the menu once the reset process is complete and push "Rescan." This will reset your channels. When the setup wizard appears, follow the onscreen prompts.
If you don’t want to reset your channels skip the third step.