Depending on the age of the TV it's possible the tuner is limited.
It's also possible the region the set was intended for didn't allow TV's access to these frequencies (Asia or Europe).
Lastly, your tuner maybe bad. You'll need to compare the specs for the Sony set to one of your other sets.
Here's some info I dug up on your Bravia TV (foreign market version):
For the Foreign market: UK Specs and the tuner info: DVB-C
For the US market model US Specs and the tuner info: Clear QAM
As you can see the tuners are not the same which could explain things if you are using this set in the US (north america).
Here's a good guide on the different countries TV frequencies: Television channel frequencies
Lastly heres a good reference on the US cable TV frequencies: Cable Television Channels vs Frequency in MHz
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