My 70 y/o father experienced spinning and blackout for few secs. could it be a tia? dad's pa won't do carotid u/s, do we need 2nd opinion?

Get second opinion: This definitely could be something serious. I would do tests to check the vertebrobasilar circulation more than the carotid circulation. But having a carotid ultrasound won't hurt. Try to see a neurologist.

Can't say: I cannot tell you that you need a second opinion, without knowing what diagnosis the pa has made or knowing the results of other tests that were done. (although, if you think you need a second opinion, that is probably enough reason already to get one.) if, on history and exam, for exam, your father has been diagnosed with something like vertigo, a carotid u/s might not be needed. Good luck.

Prevent stroke: Yes , ' blackout ' is an indication for TIA , need to consider it as serious , must be investigated , approach his doctor again , if unwilling seek help from different doctor, these simple non invasive tests

Need more info: While a "tia" is a possibility, if your dad truly lost consciousness then that is unlikely to be the cause. A carotid ultrasound is not indicated in the work-up of syncope as it would be almost impossible to have bilateral carotid stenosis that would cause a blackout. By your description a seizure or cardiac dysrhythmia is more likely. A cardiac eval, eeg, and diabetes eval would be helpful.