Best way of powering 12V DC chassis fans?

[Deke609]

I tried powering from the 12.6v heater supply with a 100 ohm dropper to slow fan speed and hence noise but in the end used a 10v SMPSU brick ; there was no noise issue's. I'd recommend trying a temporary solution and seeing how you go. I re-used the big ferrite that came with the SMPSU on the mains IP. My amp uses shielded two core with the red as hot, blue as signal ground, grounded right on the IP valve grid leak resistor, the shield is also grounded there and there only.

So, in brief, if your shielding and grounding is good, I think you should be ok.

Andy.

Many thanks Andy. I like to use a lot of shielding. Longer and straighter runs using copper refrigerant tubing (very soft and easy to bend) and copper braid for the more bendy bits -- all singly wired to ground (either one common star ground near the IEC inlet or a couple of star grounds that then tie in at the IEC). Flux bands on all transformers and chokes.

I'm very interested in your use of the grid leak resistor to locate shield and signal ground. Two noob questions: (1) what does "IP" stand for - "input" or "incoming power"? (2) where do you make the ground connection on the grid leak resistor - between resistor body and ground or between grid and resistor body? If the latter, I am guessing that this elevates signal and shield ground from the voltage potential of chassis/mains ground. Or do you elevate signal ground from chassis ground, and tie in the shielding directly to the chassis (by connecting signal ground between grid and resistor, and shield ground between resistor and chassis)?

Is using the grid leak resistor to establish a ground reference for signal and/or shielding a common practice? I.e., is this something I could read up on?

many thanks, Derek

 

[Deke609]

Use any available 12 ( 3 or 4 ). A small resistor in series will reduce fan speed

and any EMI. I don't expect the fans to inject EMI in disturbing amounts.

Many thank Peter - this is reassuring. No one has responded "Don't do it. It will inject all kinds of noise!", so I am hopeful this will work.

 

[Deke609]

FWIW, a way to hold moving air noise down is by employing good sized cheap "240" VAC fans on 120 VAC. Lots of air moving slowly is the result.

Thanks Eli. Variable speed may be the way to go. I saw that DiyAudio member Mark Johnson has posted a schematic for an analog fan speed control: Fan inside audio chassis: variable speed, temperature controlled, analog. No PWM.

I may try building it. I had good results and much fun building his Quasimodo snubber jig.

cheers, Derek

 

[Deke609]

Ηi Derek
look at the pic , i m feeding a circuit with Attiny 85 chip (slow to fast speed )-two fan option 12V 4cmX4cm fan ,from main cap of the L-Adapter circuit ,no noise at all ,activated at 42C and keeps cool the input heatsink reg HV Salas .....
6V6 line preamp

Excellent! many thanks nikosokey. Good to see an example of forced air working well. It never occurred to me to get a small fan and place it close to the particular heatsink that needs additional cooling. Very clever.

cheers and thanks, Derek