U4 burning on new Mesa 7i76e

Hello,
I'm curious if anyone can help me.
A friend and I are going to build a Linuxcnc driven Plasmacutter and we want to use named mesa to control it.
But we've experiencing some strange issues.
First, we have both an electrical background, so we've got some experiences in this stuff.

A few weeks ago, we've got our mesa, everything worked fine, but after we interfaced something on the IO (and there, we made a
mistake on our own: we've connected an Optocoupler and forgot the resistor needed bec of the 24V field power).
Nevertheless it worked fine for our first test, but the next day, when we turned on the mesa Power, U4 (driver chip) burned down with
lots of magic smoke. We've tried then to power the FPGA only, and that looked still good.
We don't know if this was our fault (too much current on output, despite the integrated overcurrent protection) so we took the pill and ordered a second one.


This time we only connected 24V on VIN and VField, and Ethernet going to our linuxcnc pc.
(See attached Pictures, jumper are placed like the schematic, both power-wires are 24V, generated from a sitop supply, polarity checked. The power is turned on and off through a DC line breaker on Powersupply Ou, both powerlines are switching on at the same
time ( they're connected in parallel after the breaker).)
And U4 burned instantly.
(Remember: No Wiring on IO, or anything else...)

At this point, we don't know what to do...
A third mesa isn't really in our budget and i don't see the point there...

Had anyone here similar issues/experiences in the past?
or has anyone a clue, what had gotten on with the second mesa (the one in the pics)?

What next steps should i take?
(i mean beside contacting the seller and mesa, it's just a little complicated because we are in Germany, the seller in Portugal and mesa is somewhere completely else)

if you use a relay or switch in the 7I76E field power you are very likely
to damage the power components

Here's the relevant section of the manual:

Field power must have a ramp up rate of less than 10V/Millisecond. This
means that you cannot switch the field power connection with a switch or relay.

tommylight wrote:

That is valid for the drives also, never switch the DC side of the power supply.

Tom,

How do you turn the power off to the drives in your systems for safety? I have read else where that putting a switch between the power supply and motor drives is not a good idea as it will destroy the drives.

I have noticed with my toroidal power supply, when power is cut off on the ac side it still has residual power and does not cut off instantly.

I don't know what type of IC is U4,.However, I suggest you google FPGA dv/dt damage and MOSFET dv/dt damage.

"Is U4 easy to replace?"

It depends if you got the right tools for SMD desoldering and soldering, but if you find the right ICs, its 'Replacable'.

"tommylight wrote: That is valid for the drives also, never switch the DC side of the power supply."

We`ve learned that lesson. For now, on the DC Side, theres a Blow-Fuse and an Switch at the primary side of the DC- Supply for the Mesa.

"thefabricator03 wrote: Tom,

How do you turn the power off to the drives in your systems for safety? I have read else where that putting a switch between the power supply and motor drives is not a good idea as it will destroy the drives."

We are cutting off the Drive Power Supplys, as tom wrote, that results that the drives a unable to turn something by their own, no matter whats happening.