My board works pretty well upto 1 000 00 Hz without fan and up to 1 200 000 Hz with (noctua) fan.
However I am still using an usb wifi card, to be able to connect with ssh.

Anyone having wifi with the built in wifi card work properly? Mine just shuts off. With an external wifi usb card, it works like a charm.

Since my 3-d printers are in the living room I i have the orange pi:s in the living room. They are primary used for octoprint. I would like to have the

built in wifi on orangepi prime to work.

You are using a very old version. Try either to update your kernel to current branch or if you have a spare sd card (which everybody should have ) grab a recent version and try again: https://www.armbian.com/download/

Thanks @Werner, I actually believed I got upgrades automatically. I have updated now by re-flashing the SD card and will supervise if wifi is stable. Seems Ok after a couple of hours, but previously it could take a day or two before the instability showed. (Now armbianmonitor -u at http://ix.io/2g61 )

http://ix.io/2glp

I have updated to latest armbian

And the built in wifi was still unstable

After a while the link goes down and I get the following in dmesg
2767.152762] RTL8723BS: linked_status_chk(wlan0) disconnect or roaming

It is annoying but no catastrophe. I run this bash script once every hour in crontab to restart wifi0

#!/bin/bash

list=`ifconfig|grep 192|awk '{print $2}'`
for l in $list; do
   #echo $list
   count=$(($count + 1))
done;
#echo $count

# if we got less than 2 interfaces, restart networking
if [ $count -lt 2 ] ; then
    echo restarting network and network-manager
    sudo systemctl stop network-manager
    sudo systemctl stop networking
    sudo systemctl start networking
    sudo systemctl start network-manager

fi