The OG-7200 is exactly like the OG-3600 except the transformer is 7KV instead of 4KV, and the transformer has a heat sink underneath.  Also, the OG-7200 has 2 ozone elements vs 1 for the OG-3600.  Here are some pictures.

Pull out, let rest on transfromer to clean ozone plates.  

Top ozone plate is one piece type, bottom one two piece plug-in type. 

No soldering needed, just remove wire cap, twist wires, and put cap back on to replace.

Fan with electrostatic pre-filter keeps the inside of the unit dust free.