Re: output current of a stepdown tranformer

Good question!  Obtaining the answer is remarkably easy; all you need is a 
DVM and a few minutes of lab time.
Step 1:  With the transformer disconnected from everything, measure the DC 
resistance of the secondary (low-voltage) winding.
Step 2:  With the primary (high-voltage) side connected to its proper 
supply voltage, measure the open-circuit output voltage of the secondary 
(low-voltage) winding. Do this as an AC measurement, in Volts RMS. Since 
you don't know what this voltage is, use extreme care in doing the 
measurement to avoid shock hazard.  Then turn off everything.
Step 3:  Divide the open-circuit voltage (step 2) by the DC resistance 
measured in step 1.  The result is the short-circuit current available from 
the low voltage secondary in amperes.

Example:
Step 1:  you measure 10 ohms
Step 2:  you measure 20 Volts rms.
Step 3:  20Vrms/10 ohms = 2 Amperes short circuit current available.  
That's your answer, 2 amps.  And by doing things this way there's no risk 
of destroying the transformer in the process.

one more time, though:  TAKE EXTREME CARE TO AVOID ELECTRIC SHOCK!!!

Good Luck!