Thanks for in advance for taking the time to read this.

No blower but I have good hi & low voltage to the breaker box, outside unit & furnace. Thermostat is good, how can I test the transformer? Thanks!
(Already have a new board 50A55 but no red light)

When you set thermostat, You have no effect, Blower/Compressor/click in air handler?
Most are 240 volt in and 24 volts ac out.
May have an onboard fuse.
Air handler needs to have power for transformer to work.