So, yesterday my Philips just would not give any picture through the scart anymore 
tested with 3 televisions, so it definitely is my beloved Philips, that's broken. Composite and audio from proprietary rca jacks work ok, so I blame some components (near scart) on the av motherboard. Or maybe it's the scart itself.
Any experiences on this particular symptom?
*edit*
The keyboard "cliks" can be heard through the scart also
check the scart solder in MSX !
Yes, will do that 
Check if you are using a Scart Cable that uses all 21 pins.... instead of cheap ass cables...
Most MSX's with scart use RGB!!!! this is maybe the reason you only hear the keyboard clicks trough the scart....
So in other words if the scart was busted and the cable was new you would at least see some Red,Green or Blue!!!
So it could have serval reasons why its not working!!!! by example your TV does not support RGB.... try this with another device like a DVD player that supports RGB 
It works now... Unfortunately I really don't know what was the reason. Changed a few capacitors (one that apparently somehow affects the sync when using scart was indeed of a wrong value!!!) The print on the pcb said something like 600 pf and the capacitor was something like 500 pf. I really don't know if that means anything, but now the computer runs like a dream and I dare to say that the image via scart is quite a bit sharper/more stable compared to the image quality before the "black out". This could be somekind of placebo effet here also 
