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Forum Index : Electronics : Problems with CNC spindle power supply

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OA47

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Joined: 11/04/2012
Location: Australia
Posts: 971
Posted: 06:38am 13 Jan 2025
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I had been running a power supply that came with my 800W air cooled CNC spindle for many years (the board is dated 2016) but I wanted software speed control of the spindle. Here is a photo of the PCB in the original power supply.




I purchased a replacement power supply that has the 0-10v input for the spindle speed control some months ago and it looks like it is from the same manufacturer. This power supply did all that was expected but occasionally shut down the feed to the spindle. This is far from acceptable, and I suspect that the unit is shutting down when certain vibrations are felt during operation as the control box is mounted to the z axis frame. I gave up on this power supply and went back to the original thinking it must have had a dry solder joint causing the problem.




Recently I purchased another of the second unit only to find that it has the same problem. I dismantled the unit and examined the PCB but could not find any suspect solder joints.

Could anyone have any suggestions?
Would very much appreciate some help.
0A47
 
phil99

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Joined: 11/02/2018
Location: Australia
Posts: 2374
Posted: 07:11am 13 Jan 2025
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Solder joints that have fractured due to vibration can look perfect. I have fond both visual inspection and meter probing can fail to find the bad one.

Just re-melting all the solder joins doesn't always work either as the high temp. and extended heating time can sometimes cause brittle intermetallic compounds to form that may ruin an otherwise good join.

What I do now is de-solder the legs of all the larger components and re-solder with 60/40 tin-lead. The smaller components are seldom the problem - but occasionally are.

In your photos the joins most susceptible to vibration would be those on the heatsink, the large diodes and the big electrolytic.

Then mount it away from vibration.

Edit
Could the shutdowns be from a current or thermal limit being reached?
Edited 2025-01-13 17:15 by phil99
 
OA47

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Joined: 11/04/2012
Location: Australia
Posts: 971
Posted: 06:21am 14 Jan 2025
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Interestingly when I removed the warranty stickers to get the PCB out of its housing I found that all off the through hole components had been re-flowed without cleaning off the flux. Looks like the manufacturer knows about the issue. I went over the joints again and removed the 110V-240V slide switch and I will re-assemble and see if there is any improvement

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