Delta found PSU rev.S1F with the original GDT (Life time 200) had PLT fail, after change to new GDT (Life time 300) Delta still found PLT fail in some unit.
After that Delta had analysis to find out root cause that is come from control loop of +48V control is very fast. So after change C607 from 220pF to 1000pF the PLT test result for both original GDT and new GDT can pass at 2.2KV.
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