We have developed a new kit, P/N 50402002, "Ext.200 lamp plate with vent", that allows you to quickly and easily upgrade Exterior 200s without the GORE-TEX membrane vent. The kit consists of a modified lamp access plate and can be installed in minutes with just a 4 mm hex key. The kit will not available for shipping before 2002-10-07 but orders may be placed now.
The air vent is an improvement that significantly lessens the risk of moisture related damage in the event that the installation does not live up to specifications. Exteriors installed "by the book" perform as intended and the vent is not considered to be a design error correction.
In those cases where there have been problems, the cause has most often been improper installation of the data and/or power cabling. As the user manual states, "The XLR connectors must be protected in a weatherproof housing. Alternatively, data cables may be connected in weatherproof electrical junction boxes, or the data cable can be replaced with separate input and output cables that connect directly inside the fixture." The vent equalizes pressure and prevents the buildup of a vacuum that can suck water through unprotected cables.
Another potential cause of problems on units up to S/N 4216060001 is leaking around the front glass. See http://www.martin.com/service/showpage.asp?id=1586.)
The membrane vent was implemented in production as of S/N 4217730001. Earlier this year, we made an upgrade kit, P/N 50402000, "Upgrade kit, Exterior 200 membrane vent", available in which the vent was installed in the power section cover. The Ext.200 lamp plate with vent is not required if you installed the first upgrade.
See also the tech note at http://www.martin.com/service/showpage.asp?id=1984.