Need help with no video from Videopac G7000

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I recently picked up a videopac G7000 with 3 games but I'm really struggling to identify why there is no picture.  

 

I'm fairly confident that the system is working.  For example if I insert a cartridge and hook up my speakers to the audio output from the motherboard I get sound and if I start a game I can hear it running correctly.

 

The video though...  Poking around the PAL encoder there is nothing on pin 5 which should be composite out.  I've been using the schematics (linked below) to try and work out what's happening but not getting that far as my board is a different revision to that in this.

 

https://ia803206.us.archive.org/14/items/G7000_Service_Manual_198x_Philips_M6/G7000_Service_Manual_198x_Philips_M6.pdf
 

Working from that schematic I can see signals on most pins on the PAL except for Burst, B-Y and R-Y.  Well there are signals there, 4.4mhz as the schematic suggests, but they are very weak less than 100mv.  Thing is I'm not sure what these should be.  

I was wondering if anyone could offer some advice as to what to test or even if they knew what the burst, b-y and r-y signals should be at?  

I'm tempted to just go with an RGB mod and bypass all the existing video output circuitry but I'd rather have it working.  

[unite]

Even if someone who has one of these was able to measure any voltage on pins 2,3,4 of the pal encoder I'd be most grateful.  It would at least give me some idea as to if the problem is where I suspect.