The WPLP transmitter has five case fans. When these fans periodically fail, I replace them. These are loud 48-Volt fans that move a lot of air. Some variants of this transmitter use 24-Volt fans. Since I didn't remember which variant this transmitter used, I brought both. Fortunately, I did have a couple of extras on hand for this occasion.
I can field-replace these fans, which saves a lot of time. The first time I did this job, I has to take the transmitter home to work on it. Fortunately, this is no longer necessary.
These 4-lead fans have a tachometer line and a PWM Speed Control Line. In this transmitter, we cut off the tachometer line and the PWM line, and the fan defaults to full speed. This is preferred at a transmitter site.
The old fan. There was free mechanical rotation with little bearing resistance, so likely the issue was a broken winding.