Is there 180 degree phase diff b/w input & output of transformer

 

No. Just reverse the leads of one of the windings.

 

Depends on how you hook it up.

 

Remember the dot notation on transformers?

http://pe2bz.philpem.me.uk/Reference/- Mini-Circuits/html/tran14-2.htm

 

not all transformers have a dot or any notation. The ones I get have two black wires (primary). These have specific connectors.

One Red, One black (secondary) and one bare (electro-shield).

There is no notation on the transformer, not dot, only a re-order number and date of manufacture.

What do you do then?

I can see that the two black are the first to be wound around the iron core. The black and red come from a larger winding (further away from the core) telling me it is a step-up trans.

 

I meant dot notation on the schematic. If you have a part in hand and don't know the polarity, you need to test it with a signal generator and oscilloscope.

 

Mains power transformers generally don't have phase notation on the input because it typically does not matter what the output phase is compared to the input.

If it's important, then you have to measure it as JMac noted.