Hmm, I have an issue with about the same setup.
I currently do not use Zener diods, but I have them on inbound so I will confirm/deny if this fixes it.
Now, I have TWO x 2 Server supplies in series.
Both of them are modified so both cases are grounded and DC side is floating.
(DL580G2 power supplies)
Both works great, all readings are good.
But, When PS1 is connected, in series, to the same AC outlet as PS2, it damage the USB output from the Charger.
Yep, strange one but since I'm working on the EOS Control suite, these kind of stuff falls in my laps.
- If I disconnect the PS1 from the AC outlet, the communication from the charger resume without errors.
- If I ungrounded one of the PS1's power supply on AC side, the communication is restored.
- If I uncouple the PS1 so they are not in series, the communication is restored.
(Note, the Charger is NOT running off the PS1, it's running off PS2)
This is not a wicked single instance where my PS is one of the kind, having other users with the EOS suite that has exact same issue.
I will see if I can measure exactly what's going on, must be some ripple somewhere as it affects another PS on same AC outlet.
I should add that I at first thought it was something at first that the computer was connected to same circuit breaker, but same effect if I use a laptop without AC power attached.
So it's the actual charger that gets affected for sure.