Those jumpers certainly exist (on all mainboards other than very early ones iIRC) amd are documented in the reference manual. And yes, on a Eruoplus (AFAIK) they've been cut/soldered to give 50Hz video timing. But note, an Apple ][ with this done does not output PAL video. What it outputs is 50Hz vertical video, but with an NTSC-like colour encoding. One of the colour difference cignals is _not_ inverted every other line, as it should be for PAL. And that's what the PAL converter board in slot 7 does. It outputs a true PAL signal. But you have to fo the cut and jumper mod too, to get 50Hz timing. I thought that was on all mainboards other than the very early ones (along with the decoding of the MSB of the grahpics memory area to give the orange/blue colours). 'Plus' to me maean Applesoft BASIC in ROM -tony