Philips CM8833 makes tikking sound

It is your audio pcb in the monitor.
Easy to fix, but be carefull.
Discription ypu will find on bas-ditta.info

The CRT shield must be grounded to the main board. If not, the charge will accumulate and discharge making the "tok" sound. Disconnect the speaker. If still persists - then it's the discharge. Otherwise the problem mentioned by Repair-Bas.
If there is a discharge, simply run the monitor in the dark, you will see it. One more thing - whenever you plan to probe anything inside, always work with just one hand.

I finally took the time to disassemble the monitor
Indeed after disconnecting the speakers, the ticking sound is gone.

@Repair-Bas:
So if I understand correctlty from your document I should desolder the audio and TTL boards, check/reflow all soldering and put them back?
Do I need to check any specific components too?

Thanks!

Thanks Bas!
I just reflowed a lot of the soldering, put it back together and it works great again!

K.