We’re not going to assume anything.
That’s what got you into this mess.
For people reading now and in the future, this is why you carefully label connections and take gobs of pictures before you tear something apart, even capture video. You can’t just plug stuff in willy-nilly and hope or expect it to work. Worst case scenario you do that and power it up permanently damage the unit. I’m not being dramatic. And I’m not saying that’s exactly what’s going on here, but in my opinion there seems to be a pattern of diving in with some level of reckless abandon and then getting lost and stumbling around trying stuff before asking for help, and then maybe or maybe not accepting the help and stumbling around some more. I can read you are now taking things kind of one step at a time and that’s good. You can even permanently damage your unit by powering it up with stuff disconnected. This is very true of the 388 with how it is designed.
According to the schematic there appears to be an 8-conductor cable with white and red connectors, the white end goes to P104 on the BUSS A PCB and the red end goes to P12 on the MONITOR PCB. I don’t know if this is this one you are asking about, I’m just regurgitating what’s on the schematic. Your descriptor “second set of pins down” means nothing to me. The PCBs and connectors are physically labeled. Please use the descriptors screened on the PCBs.
I don’t mean to be harsh. It’s just I often want to help you with these recurring situations, but I want you to learn to help yourself too by preparing and thinking ahead before you dive, in, and slowing down when troubleshooting needs to happen, especially when somebody is trying to help you. And I don’t feel like you do these things even when advised to do so and it’s frustrating…you end up killing your gear. So that’s where I’m coming from.