Esab Ultrarex UXD-P2000 Upgrade Project

With mesa powered and linuxcnc not started aout0 shows 2.8v and aout1 shows 3.3v.
These are the pins going to the drives. On the other free pins we get 3.3v. This is TB5
On TB1 (5v) I get 4.75v. TB5 is powered from the computer psu.
By the way this setup already worked and we did cut 12mm sheets.
On TB8 outpus I don’t see any voltage. I will post the ini and hal file later.
If you have any other debugging steps I’m all ears.
With aout0 and aout1 disconnected when I enable the machine there is no jolt since drives are disconnected but I still get the same error.

That likely means the 7I77 has been damaged
(or perhaps has very low 5V)

 

I changed the 5v psu for a 5.2v one. I am seeing 5.03v on the TB1 now. But same jolt and stop issue.
What do you think of the aout0 and aout1 voltages? Is that what you mean by damaged?

Yes, the AOUT voltages should be very close to 0.0V
at startup, 3.3V suggests a damaged OP amp
or a local (on card) power supply issue.

May have been damaged by a voltage transient.
Plasma tables generate large transient voltages when the
arc starts and stops. This is due to the almost instantaneous
start and stop of current flow.

This means system grounding is very important. It may be
that the PC ground path was enough different from the machine
ground path to cause this kind of damage. This might have been
prevented by having the controlling PC in the electronics case
with the servo drives, or using the 7I77ISOL card to completely
isolate the 7I77 ground from the PC.

Another possible cause of this kind of damage is a problem with the
7I77s 5V power supply. A voltage surge on the 5V supply can damage
the analog power supply and have similar symptoms.

Do the 2 yellow LEDs in the center of the 7I77 card light?
(these monitor the + and - analog supplies)

I should note that it's probably repairable
 

I see. This happened after we tried to cut with max 105amp current on the plasma to be able to cut 20mm.
I can replace any parts if you give me the part numbers. This is the second 7i77 !! It took more than 2 months I think to get this one.
And I will need any useful guidance you can think of to avoid this kind of issues in the future, please.
The mesa 5v is now supplied by an external power supply. It was provided by the pc psu up till this issue occured.
So to sum up the current situation:
When i click machine enable linuxcnc detects voltage on aout0 and aout1 and activates the soft estop. This explains why even when I disconnect the analog outputs the machine does not jolt but linuxcnc still thinks the machine is running away. Am I getting it right?
and here is a picture of the mesa leds. One red led on the bottom right side and the others are yellow. 

OK there's only one yellow LED on in the center of the board.
so that means analog power issues.

Most likely problems are:

U33 (74ACT04) bad ( can be damaged by a 5V surge to 6.5 or 7V )

Q3,Q4 (FDN337,NTR2101) bad ( can be damaged if U33 fails )

A bad OP-AMP = U3,U8,U14,U20,U28,U35 (MC33179) for channels 5,4,3,2,1,0
Note that if an OP-AMP failed, it's most likely the ones you had
connected.

I would try replacing U33 first and then rechecking.

 

 

Ok. Will try that. Thanks
Would powering the mesa board from an external source for both 5v and 24v and isolating it from the esab power supply a good option to prevent this type of issues?

If U33 is bad, that's a sign that there a problem with the 5V supply
(possible transient overvoltage) I doubt that the 24V supply is an issue.