[Amps] 4 wire EBM Papst fan but without using PWM

[Manfred Mornhinweg]

Conrad,

> I just want to know what to do with the PWM and tacho wires if 
> I do NOT want to use them.

The tacho wire is an open collector output. You can simply leave it 
disconnected, and it shouldn't cause any problem. Cut it off close to 
the fan, to minimize noise pickup, just in case. You can also ground it 
there (to the negative fan supply wire), but that's unlikely to be 
necessary.

The PWM wire is an input, intended to be driven from an open collector. 
Cut it as short as possible, and connect a bypass cap from it to the 
negative fan supply line, as close to the fan as possible. A capacitor 
value like 100nF is fine.

If after this the fan still gets interfered by the amplifier, you will 
need to install some shielding, using wire mesh where necessary, and 
bypass the fan supply lines to that shielding. Adding ferrite beads 
individually over the supply wires, close to the fan, can also help.

Manfred

========================
Visit my hobby homepage!
http://ludens.cl
========================