Can anyone help with power amplifier fan replacement

[archima2]

I'm sorry if this isn't in the right place but this is my first time using this forum.
I'm also sorry if i make some mistakes but I'm new to this kind of electricity and English isn't my native language. I bought a "new" power amplifier for my audio setup and the fan in it is very loud. I would like to replace it with a Noctua NF-F12 industrialPPC-3000 PWM. The fan in the amp right now works on 115VAC (even tho the amp works on 220VAC) and can pull up to 0.2A and it is PWM controlled even when it's on it's slowest it is loud en makes a 650Hz pitched noise.

The new Noctua fan specs from the Noctua website:
- 4 pin PWM
-Three-phase motor
-Input Power 3.17W ( typical )
-Input power 3.6W (max.)

• Input current 0.26A (typical)
• Max. input current 0.3A
• Operating voltage 12VDC (I'm pretty sure it starts working at 5VDC)

I hope anyone here can help me if not i will have to follow this video

and buy a 12VDC adapter but this would make the fan run at full speed all the time tho.
I put a picture out of the owner's manual in, if someone can draw a solution on it that would be great, the fan that needs to be replaced can be found in the red circle.

Thank you for helping me in advance or just taking the time to read everything.

 

[Avo Mk8]

Just my first reaction when looking at the amplifier circuit diagram:

When the mains transformer links are set for 220V, the existing fan effectively uses a 110V tap on the windings.
It is not a PWM fan.
It is continuously powered when the amp is switched on, through a 330 ohm resistor from the 110V tap.
There are temperature operated "thermostatic" switches on the amp o/p stage heatsinks for each channel, and if either operate, they short the 330 resistor in series with the fan, so it runs at full speed.

So if you plan to use a different fan, you could implement something similar, where the fan speed is dropped for quiescent operation, but is speeded up when the heatsink temperature switches operate.
You don't necessarily need a PWM fan to do that. Wouldn't they normally use proportional temperature monitoring, where the fan speed relates to the actual temperature of the heatsink?

I'm afraid I don't have any advice on putting in the PWM fan you have selected. Somebody with more knowledge on these might be able to suggest a suitable driver, or alternative approach.

 

[archima2]

Thank you for the quick reply.

Now I understand a little better how the current fan works. I think what you have explained is correct, when I had the amplifier open to measure everything, I indeed saw the "thermostatic switches" you were talking about.
Would it be possible that I get a 5V signal from somewhere and when those thermostatic switches short, the fan gets a 12V signal instead of a 5V signal? I'm trying to come up with a solution myself, but it may also be that my idea is useless.

 

[Avo Mk8]

If you are confident doing a bit of basic electronic design, you could create a circuit to power a fan with say 5V, and then when the temperature switch closed, it upped the voltage to 12V.
But I caution over a couple of things:
1. The temperature switches are presently in the mains circuitry, and for your proposal, they will need to be on the isolated secondary side of the power supply, so you would have to be careful to make sure no possible continuity with mains was left behind.
2. You would either have to steal some power from the amplifier supplies, or provide an additional power supply for your new circuit. Stealing power from the amp really requires some knowledge of the voltages and current available. There might also be a risk of mucking up the amplifier performance or inducing hum or other interference due to the added wiring.
It would be a shame to wreck the amplifier during the experiments!

If it were me I would try to find the correct replacement fan, or a similar one to replace it 'like for like'. Hopefully they don't all make the noise you are concerned about?

 

[archima2]

I do know someone who builds and repairs a lot of audio equipment, he might be able to help me, I'll contact him. Would it be possible to modify a power supply like this - Thomann Power Supply 3-12V DC 600mA - https://www.thomann.de/be/thomann_netzteil_universal_312_600.htm - for example, so that it supplies 5V as standard and when the amplifier gets warmer it supplies a higher voltage? And would I connect the power supply in the same place where the man in the video connects his (6:34 in the video) because my amplifier works on 220V and not on 110V?

 

[Avo Mk8]

I do know someone who builds and repairs a lot of audio equipment, he might be able to help me, I'll contact him. Would it be possible to modify a power supply like this - Thomann Power Supply 3-12V DC 600mA - https://www.thomann.de/be/thomann_netzteil_universal_312_600.htm - for example, so that it supplies 5V as standard and when the amplifier gets warmer it supplies a higher voltage? And would I connect the power supply in the same place where the man in the video connects his (6:34 in the video) because my amplifier works on 220V and not on 110V?

Personally I'm not convinced that is a practical proposition.
Not clear how you could break into that while keeping it safe, and deal with replacing its single pole multiway switch with what you have.
I was thinking of a skeleton power supply, or even a circuit built from scratch, that you could build into the amp.
Talk to your acquaintance and see what he can suggest - I'm afraid I can't give you a safe verified solution.

 

[archima2]

I can go see the person that I said he might be able to help me in a few days. Until then I'm still looking for a solution myself and while I am doing that I am also learning something new so I don't mind it. While looking on amazon I found this: - Amazon.com - https://www.amazon.com/NOYITO-AC-DC-100-260V-Industrial/dp/B07C2MMKW3/ref=sr_1_4?keywords=12v%2B5v%2Bpower%2Bsupply&qid=1692644694&sr=8 - 5VDC + 12VDC power supply this seems like something that can work. If I can now find a way that allows me to switch voltage at a certain temperature, then I have a solution right? The input range is from 100V to 260V so I could even power it on the original fan connection.