All X models that have a second iris have an additional second fan.
The younger X, such as 3,30,35 ..... there is no second iris, so there is no second fan. Therefore, the installation sites of this additional fan are covered with plates.
What is not clear here?
If you find such a fan, then it can be installed on any younger model, thereby reducing the risk of damage to the optical unit from temperature.
Last edited by Slonopot; 06-19-2019 at 01:13 AM.