Yamaha CS80

Eventually I found the problem in the PSU unit. 
Both of the resistors (1Ohm 5 Watt)  R726 and R727, made of ceramic, were interrupted. Also the zener diode D704, checked with the DVM, doesn't seem to work, in either sense no value is shown.     
Really have no clue about how this could happen...
I tested the PSU not connected to the keyboard replacing the resistors with  8 ohm ones , just to test. and replacing the metal diode with a 1/4 W   6,8 V  zener  the glass type. 

My question(s) are:    
is such a kind of standard diode good for an efficient  replacement ?

Is the value of 1.2 OHM   5 W  (the only one I have found available at the store) good or do I have to find the exact 1 OHM value?

Thanks 

Fernando