C1 on main acorn board burned right off the board <running now>

[Richard70]

Capacitor C1 burned off the main acorn board.
Only the stubs of the leads remain.
BBG heartbeat o.k. when powered by mini USB.
No heartbeat when mounted on main board.
Need to know what the repair solution needs to be.
This is powering a production CNC lathe - short downtime is critical.

Machine is a custom CNC 'gantry' that cuts blanks mounted on a standard wood lathe. The machine ran perfectly all day Saturday. To shut down, gantry was moved to zero all axis, shut down Centroid software, then shut off power to machine. All was normal.
When turning on machine on Sunday morning - no heartbeat. This is before turning on the VFD. Detached BB board and powered it with USB - good heartbeat. After removing BB board, I noticed that C1 was literally blown off the board (see previous photo).
Machine works with two cutting tools: Knife for turning round pieces and spindle for flat cuts, drilling holes etc.
To see how it works using both cutters, video (prior to dust collection mounting):
Machine has been working flawlessly, about 3-4 days a week for almost two years.

Questions:
What is meant by spindle drive isolation? The only connection from the board on this machine to the spindle VFD is the input voltage and both use a common ground.
What kind of wiring/component issue could cause this failure?

Schematic:

[martyscncgarage]

Capacitor C1 burned off the main acorn board.
Only the stubs of the leads remain.
BBG heartbeat o.k. when powered by mini USB.
No heartbeat when mounted on main board.
Need to know what the repair solution needs to be.
This is powering a production CNC lathe - short downtime is critical.

20220130_114338.jpg

Big picture please. Have no idea what kind of spindle drive, axis drives you are using nor did you give information on what led up to the failure.
I have seen that sort of damage when a spindle drive without isolation was used.

Follow this post and provide the information so we may better help you: https://centroidcncforum.com/viewtopic.php?f=60&t=1043

At this point you will have to replace the Acorn board.
From my experience, that sort of damage is not a warranty issue, rather a wiring/component issue.
Here is a link to Acorn warranty: https://www.centroidcnc.com/centroid_di ... ranty.html

Marty

[Richard70]

The burned component is not C1 as assumed. 'C1' is what can be seen initially.
Cleaned off the 'soot' from the PCB and find that the component reference is "FB5".
Removed the 24V power connector and find that iso C1, I exposed "CHASSIS".
C1 is actually located next to TP2 (test point 2).
So, what was the "FB5" component that burned?
I'm beginning to think that this is a board fault, not mine.

[cncsnw]

"FB" is a ferrite bead, possibly linking the COM (minus) side of the DC supply connection to chassis ground.

Likely something happened that caused a significant voltage (significant relative to chassis ground) to be applied to the COM side of the DC supply connection.

[Richard70]

Interesting. I will have to check all power supply grounds and chassis grounds before I put in the new PCB.

[martyscncgarage]

Interesting. I will have to check all power supply grounds and chassis grounds before I put in the new PCB.

Picture of the control cabinet would be helpful along with the chain of events that led up to the failure. What spindle drive are you using and what axis drives?
We don't want you to install another Acorn either only to have it happen again.

Marty

[Richard70]

O.K. - I'm ashamed of myself. . . Spent years designing power supplies and power supply systems, I made a novice mistake.
I daisy chained the chassis grounds of the +24V and +5V power supplies and connected the chassis ground from the Acorn board to the +24V chassis ground (see photo 1). I'm blaming it on a brain f*rt.

Ripped out the ground wires and connected them separately to cabinet chassis along with the other 6 ground wires. (see photo 2).

Now I still have another problem; the replacement Acorn board is different than my original. The relay output connector on original board has been changed to a smaller 0.1" pin space connector.
I used RL1 NO contact as a delay for the +5V power line as the Acorn board would not work if +5V came up at the same time as the +24V power.
Does the new board solve this problem? If yes - then I can rewire the +5V directly without needing to use RL1. If no, then I will have to get a matching female connector for the board.

The machine worked all day, gantry moved to zeros and then shut off. The following morning, no heartbeat on first turn on.

[martyscncgarage]

Not following what is going on in this statement (Please elaborate. There hasn't been a problem to my knowledge):
"Now I still have another problem; the replacement Acorn board is different than my original. The relay output connector on original board has been changed to a smaller 0.1" pin space connector.
I used RL1 NO contact as a delay for the +5V power line as the Acorn board would not work if +5V came up at the same time as the +24V power.
Does the new board solve this problem? If yes - then I can rewire the +5V directly without needing to use RL1. If no, then I will have to get a matching female connector for the board."


And what does this mean? Is this with the NEW board?:
"The machine worked all day, gantry moved to zeros and then shut off. The following morning, no heartbeat on first turn on."

Could you kindly take the time to provide the information requested in this post: https://centroidcncforum.com/viewtopic.php?f=60&t=1043
Have no idea what you are working with. Provide more details, "big picture"

Marty

[Richard70]

History:
Feb. 2018 connected Acorn board, found that it would not control drives.
With Marty's garage help, discovered that +5VDC to drives cannot be turned on until Acorn is powered up
Solution: +5VDC power to drives routed through RL1 on Acorn board, ensuring that Acorn is powered up before +5VDC is connected to drives.
Since then, there have been only minor setup problems and machine has run well.

Jan 29, 2022: machine ran flawlessly all day, was parked, Centroid software turned off and power to machine electronics shut down.
Jan 30, 2022: machine powered up, Centroid software could not communicate with Acorn board.
First post about problem, found that FB1 was turned into soot (mistakenly i.d. part as C1 as soot covered part of the board, 'C1' was actually the beginning of 'CHASSIS'.
Found that I mistakenly daisy chained the chassis grounds of +24VDC power supply, +5VDC power supply and Acorn board.
This mistake has been corrected, all three chassis grounds now are independently connected to chassis ground.
See photos:

Recommendation to use Centroid board swap out option and did so.

Received replacement board and found that it was different than the board I had originally purchased.
Outputs 3-8 connector changed to LEDs.
Relay connector type/style changed.
Question: Do I still need to use RL1 to delay +5VDC connection to the drives until Acorn has powered up?
If yes, do you have a mfr and part number for the mating female connector for the relay output?

Photos of the CNC lathe can be found here: https://photos.app.goo.gl/DtMH8ErhJhBQoTLk8

report_985DADEB7306-0103180445_2022-01-26_10-49-31.zip

(652.21 KiB) Downloaded 33 times

I hope you can open the screen shots document below - I use Open Office and saving as a Word doc. is too large to upload.

[martyscncgarage]

Use the new relays as you would the old.
I'm still not clear on how you wired, things. Please explain the 5VDC circuitry to the drives.
Your output assignments:
;------------------------------------------------------------------------------
; Output Definitions
; Logic 1 = OUTPUT ON (Green), 0 = OUTPUT OFF (Red)
;------------------------------------------------------------------------------

; DO NOT MODIFY
; #wizardregion Outputs
OUTPUT1 IS OUT1
VFDResetOut_O IS OUT6


Knowing what we know now, 5vdc drives work very well when connected to the DB25,
Please post a link to the manual for your drives.

Marty