Step 10.74 — 24 V rails¶
Step 75 of 80 with a helper · Chapter 10 — Wiring and Checkpoint #1
(no image — see text)
Parts:
- multimeter on Ω · tool
Do: Measure the rail once, then each 24 V input against its own ground to prove it is landed, then each side of the rail against the C14 earth pin.
Check
Every row.
Helper Records each reading the adult calls out in the table; the adult holds both probes.
What you're looking at
The authoritative 24 V table, now that the umbilical and toolboard are on the rail too. A healthy rail reads a resistance that rises; a shorted one behaves like a piece of wire. The last two rows check the rail against earth.
| Node | Expected |
|---|---|
| PSU +V → −V | finite, rising as caps charge. Never 0 Ω |
Leviathan Vin 24V + → − |
the same reading — same node |
Leviathan Vin 24-48V + → − |
the same reading — same node |
| USB adapter 24 V in + → − | the same reading — same node, now with the umbilical and toolboard on it |
| PSU +V (or any Vin +) → PE | about your +V → −V reading: the ESD bond below puts −V on PE, so this reads through the same loads (verify on bench). Never 0 Ω |
| PSU −V / any GND → PE | a few Ω — expected. This is the ESD bond from 10.58: USB-adapter GND to the frame, frame to PE. It reads OL only if that cable is missing or its washer sits on anodising |
A continuous beep on a + → − row is a reversed ferrule or a stray strand — find it now. A beep on −V → PE is not a fault; a continuous +V → PE beep is.