DZ4 A and B are both the same which turn out to be 12 volt 5 watt. for an upgrade you can only go so high on the voltage and from what NTE says 13 volts keeps the diodes cool enough. Also if you solder them in, don't push them to the board. Let them sit up some to allow total venting around the diode. I never replaced DZ1, but DZ4 A and B were toast when I initially tested them.