One of my scientific atlantic cable boxes is not receiving all the channels. Many of the digital channels do not work with at all one one of the tvs in the house. When i tried it on a different tv from a different cable line it works perfectly. Could it be a weak signal causing this problem ? I have thois upstairs cable line split 3 ways. Might a booster fix this problem?
Thanks in advance

Yep, you need a distribution amplifier. I use those made by Signal Vision and you can find them on eBay all the time at between $10 and $20 depending on how many outputs you need.

Thanks I will get one.

An Amp isn't going to solve every problem! If you have the problem on just one line then the line or an end connection may be the problem. You need to test your signal stregth before you go throwing an amp at the problem.

Three way splitter, likely with - two -7db outputs and one -3.5db. I'll bet any money that he's tried the box on the line with the -3.5db loss and that's why it works fine.

If you call your cable company, they'll probably come out and diagnose the problem for you AND perhaps even provide the equipment to rectify it for free.

An Amp isn't going to solve every problem! If you have the problem on just one line then the line or an end connection may be the problem. You need to test your signal stregth before you go throwing an amp at the problem.
Exactly. The amp might cause even more problems by overdriving the signal and/or making it even harder for the box to communicate back on the return path. Just in case I am wrong, I suggest the OP hook up the line that works with the box. Then switch from the -3.5 leg to the -7 leg and see what happens. Also, is there just the 3 way splitter upstairs or do you have another splitter downstairs?

I use a I use the Electroline EDA FT08100 distribution amplifier (drop amp).
It's designed for cable systems. It has 8 low gain outputs, with two way communications from your STB to the cable company and an output to your cable modem.