many thanks for your inputs and recommendations, that’s very useful ! I managed to plug my power supplies to the backplane and also make my Ithaca CPU board work. Well, nothing stellar at this stage, only scope traces can confirm the beast is alive…. I’m afraid that was not breathtaking enough to have my wife share my enthusiasm…
Your comments regarding the power supplies were spot on. I realized the only reason the Ithaca needs 15V is to supply +12V to this aged 2708 EPROM that I can’t even program…. I will modify the CPU board connections to have it work with a 2732 that I intend to reuse when my CPU V2 board arrives. should not be a big deal apparently. I think I will put my +15V PS aside for the moment and replace it with one +5 and one +12V supplies I will have to order to mouser.com , my case has room for three (1 large and 2 small PS units), so I think I should be fine with that, even if it is not 100% compliant to S100 standard.
I uploeaded some pictures on my temporary setup - before I install the whole shebang in my beautiful Modushop case - at http://n8vem-sbc.pbworks.com/w/browse/#view=ViewFolder¶m=Philippe%20Elie , I guess this not spectacular for you experienced guys , but that’s only my first step !! Thanks to you and this forum, I'm having great fun !