Micro mill controller is dying

[rleete]

Symptoms are the same in both forward and reverse.  Problem is recurring, but only under load.  I can drill if I keep the speed high, and take it very slow, being sure to peck drill to clear the chips.  But, press it too hard, and it stalls out, faulting.  If I run the machine with no tool, but just a mill holder, I can stall it by hand, without too much effort.

I checked things as advised on another board.  All conections are tight.  No cold solder joints.  No burnt or otherwise visibly damaged components or traces, no burnt smells.  Motor turns freely, brushes are good with plenty of life left.

Speed control pot was changed out, and it helped (at least it runs now), but it doesn't take much to stop it and have the fault light come on.

Can someone point me in the right direction?  I hate to spend $130 on a new controller board, as I just bought a mini mill, and this one is going up for sale.  But, I won't sell it if it isn't working right.

[John Swift]

which control pcb is it  , KBIC240  or XMT2325 etc

check the current sense resistor   its about 0.1 to 0.3 ohm 10w

if you can still get them ,you could use one or more tungsten filament bulbs as a dummy load in place of the motor

to try decide if its the motor current  thats excessive or the control current limit too  low

 John
 

[rleete]

The board is FC150BJ/110V.  I'll try to test the resistor.  There's about 4 or 5 of them on the end of the board, have to figure out which one.

Thanks, that the best lead I've had since whomever told me to change out the rheostat.

[dickda1]

You might also check out the GrizHFMinimill yahoo group.  Controller boards are a very popular discussion topic over there.
http://groups.yahoo.com/group/GrizHFMinimill/message/22485
I have a micro mill - no controller problems (yet).
-Dick

[John Swift]

I was unable to post a reply last night -- madmodder server busy ??


i've had a look for your control and marked the resistor on the picture

the control looks like a low power version of the FC350 with just one FET instead of two

http://www.hossmachine.info/Gerling%20Labs%20X2%20circuit%20board%20ServiceManual.pdf

      John

PS  just had a quick look for a manual for the C0 mill but they don't have the wiring diagram

     but this one  for the FC350 board should help

    http://littlemachineshop.com/reference/drawings/WiringDiagram2514.pdf

[rleete]

Foolish me, It's fixed.  I didn't realize that there are 4 adjustable pots on the board.  2 are labeled VR1 & VR2, and relate to the overcurrent condition somehow.  I decided to leave those alone.

However, ther are two more.  Closer inspection revealed them to be labeled speed and torque.  Duh.  Playing with the torque one made all the difference.  I tested the machine by mounting a block of 1/2" aluminum.  Took a 1/2" endmill, and set a depth of cut of about .15"  The machine hogged through this with narry a stutter.  So buttoned back up, and now for sale.