HD50LPW42 screen is black with antenna inputs

sounds to me like the signal strength from the samsung galaxy

In settings you have to run auto scan to find signal.
Should work for both TV's

Try checking the signal strength then run the scan again.
Checking the DTV signal strength
You can check the DTV signal strength to determine if you need to adjust your antenna or digital cable input. The higher the signal strength, the less likely you are to experience picture degradation.To check the DTV signal strength:
1.Press MENU. The on-screen menu opens.

2.Press < or > to highlight Channel, then press v. The Channel menu opens. The DTV signal strength is shown at the bottom of the menu.

3.Press EXIT to close the menu.

you need to get a digital aerial first .then you can sort out any other problems from there

No,Ur Digital antena not getting a good signal,because of lanscape like hills or big buildings,blocking the signal,that why u not getting good signals,or no signals at all.Buy another name brand digital antena with a stronger signal amplifier.Or buy a digital roof antena,well help or solved these problems.

Are you using the coaxial cable to connect the converter box to the set, or have you hooked it up with rca type video cables? The latter are highly recommended if you want a better connection and have audio/video inputs on the back of your television. But you don't want both A/V & coaxial.
Also be aware that some older antennae will not pick up digital signals well. Try to use a coaxial cable all the way up to the antenna junction. Find out where most signals are broadcast from in your area and aim the antennae appropriately. (Use a compass.) See helpful link here. Your converter remote should have a signal strength button that you can use to check the various channel strengths. If you're using a coaxial link to the tv and have little signal strength, expect a poor picture. You'll also want to select the Mono option for Audio Output in the converter menu.
Finally, depending on the age of your set, if you're using rca video inputs, use the TV/Video button or the AV button on the TV or universal remote to switch the input from the channel on your TV to the video 1 setting (or whatever picks up the digital converter signal) so you'll get that clear signal. Then you can use the converter remote to change channels, adjust volume, etc.

you have to take the remote, find the input button, push the input button untill your picture comes back, you should see the input go from cable/antenna, to vid 1--vid2---vid3---if pushing the button a couple of times dont change it, you will have to hit the input button, then arrow down, and select the nexy one, do that untill you find the picture

What is your TV input connection? Are you using Antenna? Cable? Dish?

The Unusable Signal sounds like the TV is not getting a signal. Does your TV have a built in HD Tuner?

If you are using Antenna you might want to try setting up the connections and it should search for quality channels that you get good signal strength. If you are on channel 2 and there is no over the air channel 2 it may say "unusable signal".

I have the same problem using HDMI cable, I was able to get it working using composite or RCA
cables. I still cant get it working on none of the 3 hdmi inputs

l have a 42 in tv rca connected from a direct satellite and i have no picture or sound tryed different connecters only black screen with unsable signal