Blown stepper driver

After doing some test cuts yesterday I'm doing the first real milling on my TravelCNC today.
I want to find out if it doesn't loose any steps now.

First problem:
after switching it on there was smoke any my Y-stepper driver went belly up.
The FMD2740A stepper driver is rated  for 12-50V DC input.
Internally they use an LM2576S-5.0 to generate 5V.
Maximum input voltage 45V.
...They do not use the LM2576*HV*S-5.0 with a maximum input voltage of 60V.
And I'm using a 48V power supply.
....go figure.

Update: The chinese dealer very forthcoming and is even offering to pay for the repair (shipping to china and back to get a replacement with the same chip is expensive, time consuming and not a permanent solution).

I now connected the Y stepper to the A channel, set MACH3 to interpret the A channel as  a linear axis and search&replaced the axis in the g-code.
It's not cutting.....
The operation will take 2x 1h . That should be enough to detect any lost steps. Particularly in Z.
Touching the hand weels on the steppers there is no jittering. So it looks good.

Update: Test was a SUCCESS. No lost steps whatsoever anymore!!! Very smooth operation for multiple hours and interrupted with shutting down the machine for a night before resuming.

Update: My replacement FMD2740A died too. (during 30C3) Post mortem showed a bad solder joing on capacitor 1.

Update:  2 other stepper drivers blown. Dealer "Thomas Wu" confesses they are only good up to 45V. Not 50V
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