Korg Forums

SeedyLee · Posted: Sun Apr 28, 2019 10:56 am Post subject:

During a recent service of my 2011 Kronos, I decided to replace the fan as the factory unit was becoming progressively noisier. (Incidentally, the stock fan is rated for around 30,000 hours of use). Like a few others, I tried the Noctua NF-A6X25 FLX as it was readily available in my region and should be a high quality fan.

I found this fan was still quite noisy on "Auto" mode, but on "Slow" it didn't seem to move enough air to keep temperatures low. On my unit, temperatures were getting up to 80 degrees in a 29 degree room. On auto, the fan speed was much higher, but it still wasn't full speed. It also made an annoying humming sound due to the pulse width modulation.

I entered test mode (Hold Mixer Knobs, Reset Controls, Enter, 2) and actually found it to be quieter on higher fan speeds.

What I discovered is that the Kronos controls fan speed using its own algorithm in the EVA module, and it uses preset fan PWM values that work reasonable well with the stock fan, but don't necessarily work optimally with aftermarket fans. It updates the fan speed about once a second between two values.

I modified my Kronos to use the native Linux WinBond fan speed control algorithm instead, by (essentially) adding these two lines to my inittab:

GregC · Posted: Sun Apr 28, 2019 4:07 pm Post subject:

SeedyLee · Posted: Mon Apr 29, 2019 6:40 am Post subject:

SeedyLee · Posted: Sun May 05, 2019 4:49 am Post subject:

Okay, so a little more information about fan control on the Kronos.

The speed (and hance noise) of the fan is controlled by a Winbond W83627THG-I Super I/O controller using pulse width modulation (PWM). This is controlled by the Linux W83627HF driver, the source code for which can be found here: https://github.com/torvalds/linux/blob/master/drivers/hwmon/w83627hf.c

The Winbond controller has two registers which directly affect the mechanical performance of the fan: PWM width (or duty cycle), and PWM frequency. It appears only PWM Width can be adjusted at runtime via the sysfs on the Kronos - PWM frequency is hardcoded to a static value. Unfortunately, depending on the fan, the PWM Frequency may not be optimal and may produce harmonic noise (buzzing etc).

If your aftermarket fan is humming or buzzing, it may be because the PWM Frequency isn't suitable for the mechanical characteristics of that fan. The easiest option is probably to adjust the fan speed electrically using a resistor in serial, and run it at a duty cycle as close to 100% as possible.

It's also worth mentioning that the minimum speed via PWM control differs from fan to fan, so some fans may stop when the Kronos is set to "Slow" fan control.

My advice: stick with the stock fan. Other fans may appear to have similar performance characteristics, but the Kronos works optimally with the factory fan from a noise perspective.
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Current Equipment:
Korg Kronos 2 88, Reface CS, Roland JV-1080, TE OP1, Moog Subsequent 37, Korg ARP Odyssey, Allen & Heath Zed 18, Adam F5, MOTU MIDI Express XT, Lexicon MX200 & MPX1, Yamaha QY700, Yamaha AW16G, Tascam DP008ex, Zoom H6, Organelle, Roland J6 & JU06A

Previous: Triton LE 61/Sampling/64MB/4GB SCSI, MS2000BR, Kronos 1 61, Monotribe, NanoKontrol, NanoKeys, Kaossilator II, Casio HT3000, Roland VP-03, Reface DX, Novation Mininova, MPC One

average_male · Senior Member Joined: 07 Feb 2011 Posts: 278

Poseidon · Senior Member Joined: 08 Jul 2018 Posts: 373

SeedyLee, did you consider the Arduino Micro board running independently.
There are enough PWM channels to control not one but two fans.
And there are 12 analog inputs for sensor.
Such project would definitely be easy and perhaps even better what Kronos has to offer.

SeedyLee · Posted: Thu Jan 13, 2022 5:19 am Post subject:

Hi all,

I recently purchased a new fan to replace the Noctura I've been using for a while. However, I seem to have lost my original screws!

Can anyone tell me what type of fan screws ship with the Kronos for securing the OEM fan? I believe it's a 4mm x 30mm, but the M4 screws I have tried don't fit the thread. I'm wondering if they are perhaps a .5 pitch screw, as opposed to the more typical .7 pitch M4s?

Korg don't appear to sell them as a spare, and the service manual is cryptic in this area.

If anyone has any info (or even pictures), I'd be incredibly appreciative!
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Current Equipment:
Korg Kronos 2 88, Reface CS, Roland JV-1080, TE OP1, Moog Subsequent 37, Korg ARP Odyssey, Allen & Heath Zed 18, Adam F5, MOTU MIDI Express XT, Lexicon MX200 & MPX1, Yamaha QY700, Yamaha AW16G, Tascam DP008ex, Zoom H6, Organelle, Roland J6 & JU06A

Previous: Triton LE 61/Sampling/64MB/4GB SCSI, MS2000BR, Kronos 1 61, Monotribe, NanoKontrol, NanoKeys, Kaossilator II, Casio HT3000, Roland VP-03, Reface DX, Novation Mininova, MPC One

voip · Platinum Member Joined: 27 Nov 2014 Posts: 3772

Which Kronos version? I vaguely recall the screws on a Kronos X being of the "self tapper" type. Darned if I can find them now....Found them!! They are, indeed self-tappers, so more like a fine-pitched wood screw, outside thread diameter 3.90mm, pitch 1.45mm, length 30mm. There were three screws, not four!

The part number is: BT P 3BBC 4x30: 3 (3-off).

The M4 18tpi screws in this link might be close enough:

http://www.japanesescrews.com/products/class-2-tapping-thread-for-use-in-metal-or-plastic.html

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SeedyLee · Posted: Thu Jan 13, 2022 11:22 am Post subject:

You are amazing! That would explain why I couldn’t get the other ones to fit!

I will see what I can find that match those dimensions, but that’s a huge help.

Korg don’t stock those screws as spares, and the part number didn’t bring anything up.

In the meantime I have just used some M3 screws with nuts and washers to oss through the existing holes. Seems to have done the trick.

Will also post my findings with this fan - so far, so good though. I tried to find one that matched the specs of the OEM one as much as possible. Though I had to solder on my own 3-pin Molex connector as it came from Mouser I terminated.
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Current Equipment:
Korg Kronos 2 88, Reface CS, Roland JV-1080, TE OP1, Moog Subsequent 37, Korg ARP Odyssey, Allen & Heath Zed 18, Adam F5, MOTU MIDI Express XT, Lexicon MX200 & MPX1, Yamaha QY700, Yamaha AW16G, Tascam DP008ex, Zoom H6, Organelle, Roland J6 & JU06A

Previous: Triton LE 61/Sampling/64MB/4GB SCSI, MS2000BR, Kronos 1 61, Monotribe, NanoKontrol, NanoKeys, Kaossilator II, Casio HT3000, Roland VP-03, Reface DX, Novation Mininova, MPC One

voip · Platinum Member Joined: 27 Nov 2014 Posts: 3772

The original Kronos X fan was too noisy for a quiet studio environment, so I fitted a quiet fan using some compliant rubber "pull through the hole" mounts, resulting in the Kronos fan being almost totally silent in operation. The only time I can hear it is after several hours use in hot weather, probably down to wear in the fan bearings.

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SeedyLee · Posted: Mon Mar 21, 2022 2:26 am Post subject:

Which fan did you replace the stock one with, voip?
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Current Equipment:
Korg Kronos 2 88, Reface CS, Roland JV-1080, TE OP1, Moog Subsequent 37, Korg ARP Odyssey, Allen & Heath Zed 18, Adam F5, MOTU MIDI Express XT, Lexicon MX200 & MPX1, Yamaha QY700, Yamaha AW16G, Tascam DP008ex, Zoom H6, Organelle, Roland J6 & JU06A

Previous: Triton LE 61/Sampling/64MB/4GB SCSI, MS2000BR, Kronos 1 61, Monotribe, NanoKontrol, NanoKeys, Kaossilator II, Casio HT3000, Roland VP-03, Reface DX, Novation Mininova, MPC One

voip · Platinum Member Joined: 27 Nov 2014 Posts: 3772

Not 100% sure which one was used in the end, as several different fans were bought and the best one picked, but I think it was the Noiseblocker XR2. Make sure it is supplied with the rubber mounting plugs.

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hephiroth · Joined: 22 May 2021 Posts: 31