Hi Jerry,
Nothing helped to get rid of the oscillations when using my testload. True oscillation, about 12 MHz. So as a final attempt I also made sense lines connections, something I never did before. Against my expectation this cured the problem! There still is some switching noise in the rhythm of the inverter, but the DC voltages are fine now.
This is the final configuration (|| means in parallel):
+/-50V both 470R || 1k5, both 10uF to GND
+/-15V both 22R || 22R, both 100uF to GND
+5V 6R8 || 6R8, 100uF to GND
+5VL 5R6 (to GND Lights, I did not connect pin 3 and pin 7).
No other ground wires, except earth from chassis PS to chassis main frame to be on the safe side. All loads via the 10-pin LV connector and the 6-pin Sense connector. So nothing at the 54V lines for the HV supply.
I didn't try it yet with less load, and I added the caps (values taken from the Main Interface Board) before I added the sense lines. So maybe these are not (all) needed. Anyway the result could be used as a guide I think. I used forced cooling; some resistors had to dissipate a little more power more than rated for.
Albert
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I would expect the sense lines to be needed? They are directly connected on the interface.
Jerry Massengale
