DIY 5k Monitor - success :-)

[PaulD-UK]

@TheCluelessOne "If I were to have the fan always run (when the board is on? but at the lowest RPM possible to keep it quiet what would be the best way to do it?"

Which fan? The original iMac fan needs a 24V to ~12V buck converter and a proper 4 wire PWM controller.
The iMac fan works at any voltage from 12V down to 5V, but just using a lower voltage doesn't make it quiet.

With a 4 wire PWM controller it will run at a far lower speed and be completely silent, especial if you lower the voltage to less than 12V. I run mine at 10V, but it will work down to 5V.

There are three PWM controller boards people have used:
The Noctua NA-FC1 is the easiest.
Or these two.

Youmile Fan Speed Control Module,Thermostat PWM Fan Module,DC 12V 3A 4-Wire PC CPU Fan Digital display Speed reduction and noise reduction with NTC temperature probes DC female connector

The Fan speed control module can automatically adjust the speed of fan according to the actual temperature.When the temperature is too low, it can made the fan stop running,easy wiring, and adjustable PWM fan speed. Specification: Supply Voltage: DC 12V Voltage Range: DC 8~16V Cricuit Dissapatio...

www.amazon.co.uk

VOANZO PWM Standalone Fan Controller DC 12V 4 Wire Thermostat PWM Fan Speed Controller DIY Module Board for PC Fan Temperature Control

Features: TFL (No. 1): The minimum PWM setting of the temperature control channel. The minimum PWM of FAN1 is 40% when in the ON state and 20% when in the OFF state. TP1 TP2 (No. 2, 3): The temperature control channel controls the temperature zone. The specific settings are as follows (need to be...

www.amazon.co.uk

A 47Ω resistor will not work with a 4 wire fan.
It's only a solution for the 2 wire fan in the R1811 heatsink, and that needs a 150Ω resistor.

 

[PaulD-UK]

@JakoDel "...the best boards that don't use ancient awfully inefficient chips which require active cooling (absurd if you ask me) are the FA1/SA1. Am I correct or is there anything better, ideally with working volume control? And what quirks are you talking about?"

The JRY-W9RQUHD-SA1/FA1 boards have good modern hardware, but the firmware isn't as well developed as older R1811/R9A18 boards.

The JRY boards don't have proper DDC/CI control implemented.
DDC works for brightness control (so Better Display, or Monitor Control etc works), but not for audio. To control audio volume you need to use eqMac software.
The R1811 is DDC compliant for video and audio, except for remote computer controlled input switching, which only works for DP and USB-C.
It just has the usual Auto-detect, or manual remote switching.

There appears to be IR remote hardware built into the JRY boards, but the firmware doesn't implement it.

In testing, the R1811 board seems to be more efficient, and use less power than the SA1, but there's not a huge difference.
So there are no 'ancient awfully inefficient chips' being sold today for 5K conversions.

All these boards were originally manufactured for use in 4K/144Hz monitors, and the older boards have had more development to make them work well at 5K.
Newer boards are a bit cheaper, partly because they haven't received the development effort to eliminate the 'quirks'. 😉

The R1811 has a fan cooled heatsink to allow it to work sealed in an enclosed iMac case with no risk of overheating. It's not 'absurd', it's a design choice to reduce the size of the heatsink to allow easier installation...

What is 'absurd' is not taking steps to acoustically insulate the noise of any fan from the outside...
Controlling any fans to run at reduced RPM is part of the solution. These conversions can be well cooled, and run silent.👍

 

[TheCluelessOne]

@TheCluelessOne "If I were to have the fan always run (when the board is on? but at the lowest RPM possible to keep it quiet what would be the best way to do it?"

Which fan? The original iMac fan needs a 24V to ~12V buck converter and a proper 4 wire PWM controller.
The iMac fan works at any voltage from 12V down to 5V, but just using a lower voltage doesn't make it quiet.

Apologies, wrote that on my phone so was a little brief.

I'm using the SA1 board coupled with the 200w meanwell PSU, and want to reuse the original iMac fan. Ideally at its lowest setting but just have it on constant (when the board is on) as oppose to variable based on temps. How could I achieve that?

A 47Ω resistor will not work with a 4 wire fan.
It's only a solution for the 2 wire fan in the R1811 heatsink, and that needs a 150Ω resistor.

This is what happens when you use ChatGPT for solutions lol

 

[PaulD-UK]

@TheCluelessOne Here's the connections to a Noctua NA-FC1.
This will give you fan speeds down to about 5 revs per second = very slow. 😯

The colours of the wires in this photo don't match Noctua's - they use Black –, Yellow +, Green Speed, Blue PWM, but the wire positions and labels in the photo are correct.
Note the crossed over + and – wires, Apple 'thinks different':

 

[Rip57]

Back in business. Found a new screen (B1 variant) to replace my recent screw-up (see nicked ribbon cable). Screen works at 5K. Now I'm back to wiring up the crossover circuits and figuring out how and where to mount everything.

 

[braunico]

Hi everyone,

Quick feedback on temperature with the SA1, using my build.

• Temperature room is around 19°c
• Ram door was kept open during tests
• PWM controller probe directly on the SA1 heatsink (with kapton tape)
• 12V input on stock fan

Condition	PWM settings (L,H,C)	Stabilized temp
• Playing game with DP • No USB-C Charge	OFF	64.4°
• Playing game with DP • No USB-C Charge	45-80-30	49,4°
• Playing game with DP • No USB-C Charge	45-60-30	47.4°
• Playing game with DP • USB-C charge a MB Pro	OFF	70°
• Playing game with DP • USB-C charge a MB Pro	45-80-30	50.3°
• Playing game with DP • USB-C charge a MB Pro	45-60-30	48.1°

NB: note sur what the C is compared to L, was always set to 30
Not sure what is a "good" temperature, everyhting under 50 seems fine to me.
Paul what's the point of lowering the fan voltage compared to a lower PMW signal?

N.

 

[PaulD-UK]

@braunico The only information I have found is not to run the scaler chip at more than 65°C, with the heatsink a bit lower than that.

The original iMac fan can draw well over 1 amp at a very noisy full speed - which is too much in a conversion.
Running it at a lower voltage reduces the amount of noise it will make if the controller speeds it up.
The PWM voltage is set by the controller and should not be altered.

For comparison the R1811 (with its heatsink fan) doesn’t seem to get above more than about 40°C even with the heatsink fan running at lower voltage.

 

[TheCluelessOne]

@PaulD-UK the Noctua is nice, but it’s also £20. I have two screens so the cost takes it out of the equation for me, I can likely get all the parts I need x2 for the price of that single unit.

I’ve had a look on AliExpress, would the following parts be what I need?

Buck Converter

￡4.01 | LM2596 DC DC Step Down Converter Voltage Regulator LED Display Voltmeter 4.0~40 to 1.3-37V Buck Adapter Adjustable Power Supply

￡4.01 | LM2596 DC DC Step Down Converter Voltage Regulator LED Display Voltmeter 4.0~40 to 1.3-37V Buck Adapter Adjustable Power Supply

a.aliexpress.com

PWM controller

￡5.07 | DC 12V 24V 48V 5A Digital Display Four-wire PWM Motor Fan Speed Controller Governor Temperature Control Support EC EBM Fan

￡5.07 | DC 12V 24V 48V 5A Digital Display Four-wire PWM Motor Fan Speed Controller Governor Temperature Control Support EC EBM Fan

a.aliexpress.com

Can I assume that simply placing the thermistor on either the PSU or the boards heatsink will be sufficient to have a constant speed only when it’s on?

I’ve noticed the thermistors come as a probe and a ring buckle, is there anywhere I could attach that?

 

[PaulD-UK]

@TheCluelessOne
Both those look fine.
It's difficult to attach a temperature probe to the SA1 heatsink, and doing so will speed up the fan as it will get hot...
@braunico managed to stick a probe on the heatsink with Kapton tape, which is fine for testing, but may mot work long time.
Since the fan will cool the air in the case down, as it's airflow may not be directed at the heatsink, I think putting the probe somewhere higher in the case than the heatsink would be OK.

 

[TheCluelessOne]

@TheCluelessOne
Both those look fine.
It's difficult to attach a temperature probe to the SA1 heatsink, and doing so will speed up the fan as it will get hot...
@braunico managed to stick a probe on the heatsink with Kapton tape, which is fine for testing, but may mot work long time.
Since the fan will cool the air in the case down, as it's airflow may not be directed at the heatsink, I think putting the probe somewhere higher in the case than the heatsink would be OK.

Would just sticking the probe to the enclosure of the iMac suffice? Behind the Apple logo perhaps?

Will the combination of parts I’ve shown you simply run the fan at a constant speed or will it vary depending on temp? I actually only want it at the lowest setting.

 

[PaulD-UK]

@TheCluelessOne
The point of the temperature probe is to allow controlled speed up of the fan when the iMac interior gets hot.
If you don’t want this then you just set the speed up temperature setting on the controller board to be higher than it ever gets.
The probe can be anywhere, by the logo is fine.