1.2V, 1.8V, 3.3V, 5V are all LTC3850
There are 3 sequencers LTC2928
The second sequencer is U497 and 1.2V is the 4th supply
You only need the main supply + the sequencer powersupply cable attached to test
1.8V, 2.25V(2.17V on silkscreen), 1.6V all come up to voltage
1.2V has no output
EN4 signal on sequencer is present and has continuity to RUN1 and RUN2 of LTC3850
V4 signal on sequencer has continuity to output
Mosfet gates are directly connected to LTC3850 TG1/2 BG1/2 pins
No gate signal on all 4 mosfets
1.2V LTC3850 all pins to ground measure out very closely matching V1.8 LTC3850
Reworked area and no difference
Everything is pointing to LTC3850 being bad. Ordering a new one.
Also I am almost 100% sure the power switch that breaks on these often is JN2UOANAGX