Changes

===J-12 Power-Input Topology===

J-12 carries three transformer secondary windings plus a single ground-tie wire. The transformer itself has no center tap or earthed reference — the system ground is '''established on the board''' by bonding the negative DC output of one rectifier to the positive DC output of another, using the lone green wire. This stacks two of the rectified supplies end-to-end to produce the bipolar ±V_unreg rails feeding the ±15 V analog regulators, while the third (blue) winding feeds an independent positive rail for the digital regulators.