Originally Posted by FOX TV

Try the converter box on another TV. How do you feed this TV? Are you using the coaxial output, or the audio / composite video ( the Red/white/ yellow connectors on the back of the box ) If using the coaxial output, that could be a faulty RF Modulator in the converter box or the TV.

Feeding converter into VCR, out of VCR into TV using the audio/composite video cables.


Does your signal pass through a VCR, as it could have a faulty or drifting RF Modulator too. That signal looks as if it is being produced by some type of modulator, based on what looks to be part of the Vertical Blanking Interval, or line 21 data (CC DATA) at the top of the black box.

No modulator I think since am using audio/composite video cables.

Does any of your equipment have picture in picture capability?

No 'picture in picture', simply too old TV.

If so, something could be triggering it to come on. Try using the audio / composite video connection if you are not using it now. The TV may have some bad or failing capacitors that can also cause that symptom, especially if it is an older set with a lot of hours of use on it.

Ok, you are referring to drying out high ESR filter caps. Sure is possible.

Hook up a different box to that same TV and see what you get. Just change stuff around and see if the problem follows the box, or does a different box hooked to the same TV produce the same results on that TV?

Originally Posted by Dave_s

Certainly can run this TV with different box.
Lots of trouble shooting for me to do. Many thanks.

Originally Posted by FOX TV

Failing capacitors can certainly cause this issue, but normally if it is a capacitor issue, the black box will normally be stationary, and not drift around the screen. We have replaced many a capacitor in CRT monitors, and that usually fixes any problems similar to this one.

Originally Posted by Dave_s

I do think the size and position of the very black box is constant.
I did reset the BOX CC option back to factory 'Default'.
Have not seen the black box since.
If seen again, then swapping boxes is the next step to determine if box or OLD SHARP TV is the source.

Originally Posted by Dave_s

I do think the size and position of the very black box is constant.
I did reset the BOX CC option back to factory 'Default'.
Have not seen the black box since.
If seen again, then swapping boxes is the next step to determine if box or OLD SHARP TV is the source.

Originally Posted by HTNut

Hmm, do you have CC (Closed Caption) enabled? The placement of the black rectangle looks a little high for that though.