I picked up Keithley 2304A as "For parts or not working".
And not surprisingly it does not work
I found blown 3A fuse in the power supply, but the replacement one also did not survive for long.
So I guess that the VICOR module is dead.
But before I replace the module, I am worried that it died.
I measured the input to the module, and it's 460V (!). The module is rated to 400V only, so it's not surprising that it died. (My mains are 110V.)
They are probably using MAX34262. I guess that schematic follows what datasheet
https://www.onsemi.com/pub/Collateral/MC34262-D.PDF suggests,
with half of sense voltage divider on the top, half on the bottom of the board.
I measured 568K from pin1 to V+ and 6.4k from pin1 to GND.
The 6.4k seems to match the SMD values of \$6040\ Ohm + 357\ Ohm = 6397\ Ohm \$. I did not desolder R207, which seems to be the other side of the divider, but cosmetically it's in good condition. The value is hidden exactly underneath, unfortunately.
If I understood datasheet correctly, the output should be \$2.5V * (\frac {568,000} {6,400} +1) = 224.375V\$ (there is formula on page 10 of the datasheet).
Which seems to be exactly twice lower from what I measured!
Could somebody with working 2304A measure the input voltage to the module (I labelled the testpoint +400V), and the feedback resistor values (between PIN1 to GND and PIN1 to +400V)?
Before I start desoldering random components, is there something obvious that I am missing? Which component is the most suspicious and should be tested first?