Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Baguette on March 11, 2012, 05:51:11 am

Title: AC cooling fan switching pops
Post by: Baguette on March 11, 2012, 05:51:11 am

Hello,

So, I've added this AC cooling fan at the PT primary.
I've included one of those nifty 3 positions switch so I can have the amp off, on or on with fan.
Now, the problem is I have pretty loud pops everytime I filp the switch (on or off).

I'm wondering if there's a way to kill those noises. Like adding a cap somewhere.

???

Thanks for your answers.

Title: Re: AC cooling fan switching pops
Post by: Baguette on March 14, 2012, 05:03:18 am

Any tip?

Title: Re: AC cooling fan switching pops
Post by: stratele52 on March 14, 2012, 05:29:51 am

Pop only with the fan ? Or fan disconnect and no pop ? What kind of fan's motor  ? Picture or name model.

Question; is it your switch wiring or the add fan the problem ?

Title: Re: AC cooling fan switching pops
Post by: birt on March 14, 2012, 05:53:30 am

you could try a 2M2 resistor over the switch. (i'm assuming it's a 12V fan)

Title: Re: AC cooling fan switching pops
Post by: Shrapnel on March 15, 2012, 02:47:55 am

Quote from: birt on March 14, 2012, 05:53:30 am

you could try a 2M2 resistor over the switch. (i'm assuming it's a 12V fan)

Quote from: Baguette on March 11, 2012, 05:51:11 am

Hello,

So, I've added this AC cooling fan at the PT primary.
I've included one of those nifty 3 positions switch so I can have the amp off, on or on with fan.
Now, the problem is I have pretty loud pops every time I flip the switch (on or off).

So what I understand here is... AC fan hooked to the mains (PT Primary) via s three position switch. Off 1-on, 1 & 2 on?
Since installed it pops when the power? switch is thrown. Before it was installed, no pop.

Does it pop irregardless of standby switch settings?
Are the wires for the fan ran with the other AC mains wiring, or do they get close to the signal paths?
Where is the fan mounted in respect to the rest of the amp?
(Remember, we keep the AC mains wiring away from the rest of the signal paths to avoid noise, AC fan should be no different.)

Title: Re: AC cooling fan switching pops
Post by: Baguette on March 16, 2012, 08:15:00 am

Thanks for the answers.
Here's more bits of info:
- the fan works on 230AC line voltage NOT 12 volts.
- it has 2 identical wires and reversing them does not change the air flow direction
- it's positioned the furthest away from the preamp.
- the pops are un affected by the preamp controls (appears even when volume and tone stack turned off)
- there's no standby on the amp.

Hope this helps your diagnostic. Any info is appreciated.