P600 connects the base of the 2N2907A either to ground or to the collectors of
the transistors which perform the (B7 XOR A16) function.
Thanks a lot Richard! It really looked as if the third pcb pin was isolated from the rest and was only there to keep the jumper save in non-gnd position. So I simply left the jumper out when trying things! This also means that interdot blanking enabled/disabled is not the correct description for the P600 positions. It's always enabled (except when left out) and enables/disables B7/A16 function you mentioned.
Now I put P600 in the non-gnd position and tried things again. And yes, now I get interdot blanking leakage in the 7A26 trace. I added a photo to your album.
As I said, my board has no P600. The collectors of the XOR transistors and the base of the 2N2907A are directly connected by a trace on the non-component side of the board.
Where is P600 located on your board? I don't see it depicted on the board illustrations of any of the manuals I have looked at.
For this I also added a photo.
Albert
