Micro-Mill Switch Problem

[max corrigan]

This is not really a machining question, so i hope it's in the right spot, i have a problem with the electrical switch on my micro mill Sieg 1
It will switch on OK, going through the usual procedure ie switch for forward or reverse, get the orange and green lights on! then turn the other knob back anti clockwise till it clicks then clockwise till you get the correct revs, and just the green light,
So far so good! then i start taking a few light cuts with a small end mill, no more than 2 thou or less, after a short while, the revs momentarily increase, the orange light comes back on and the machine cuts out, this can go on for several times until it will not start at all, ie both lights stay on, the next day it will start OK then it will go through the same procedure
Anyone else had this problem? maybe there is a simple solution (i hope)as i am ne electrical expert!
I thought at first it might be dampness, and tried to gently dry out around the switch area, with a heat gun, but it made no difference
I hope someone can help, (in the simplest possible terms)
Regards Max

 

[black85vette]

I had a problem similar to that on my X2 and it turned out to be a bad solder connection on the motor control board. Get the mill running then tap on the housing of the controller with something that won't damage it. See if it has any effect. You could also pull the cover off and wiggle the wires (a very advanced technical procedure) and see if you get any results. Keep fingers and metal tools away. Use wood or plastic.

This could be as simple as a cold solder joint.

 

[max corrigan]

I had a problem similar to that on my X2 and it turned out to be a bad solder connection on the motor control board. Get the mill running then tap on the housing of the controller with something that won't damage it. See if it has any effect. You could also pull the cover off and wiggle the wires (a very advanced technical procedure) and see if you get any results. Keep fingers and metal tools away. Use wood or plastic.

This could be as simple as a cold solder joint.

Thanks black85vette for your quick answer, i did as you suggested ie start mill, then gave it a clonk with a nylon mallet, and sure enough the orange light came on, and the machine stopped
Took of the covers tightened up all the screws i could find, most of which were finger tight, pulled on all the wires, all tight! visually checked the soldered joints could see nothing amiss.
Re-assembled everything,started up, gave it a clonk,on came the orange light and the bloody thing stopped again!
So as you seem to suggest something is loose somewhere,what puzzles me is it starts the next day
I do not have the know-how and electrical meters to check further, so will have to abandon it for the time being!unless you or someone can suggest another method!
Thanks again for you suggestions, i thought i had it cracked with all the loose screws etc.and your very advanced technical method!but it was not to be
Regards and thanks Max............

 

[black85vette]

Here is another high tech approach: Mark all the wires and pull the board out and visually inspect the solder pads. You can wiggle the components as you do this. The little nubs (very technical term) should NOT move when the part is wiggled. Also, on many cold solder joints you will see a little "ring" like a bullseye which is a crack around the component lead. I have found many bad joints just by looking. No need for a meter or o-scope for this. Sometimes you can use something non-metalic like a chop stick to probe around while it is running and see if you can isolate the wire or part that is intermittent. This may not be frequent but appears to be somewhat common on these units. On mine it ended up being the big transistors attached to the heat sink.

If the machine is under warranty I would just try to get a new control board.

 

[max corrigan]

Here is another high tech approach: Mark all the wires and pull the board out and visually inspect the solder pads. You can wiggle the components as you do this. The little nubs (very technical term) should NOT move when the part is wiggled. Also, on many cold solder joints you will see a little "ring" like a bullseye which is a crack around the component lead. I have found many bad joints just by looking. No need for a meter or o-scope for this. Sometimes you can use something non-metalic like a chop stick to probe around while it is running and see if you can isolate the wire or part that is intermittent. This may not be frequent but appears to be somewhat common on these units. On mine it ended up being the big transistors attached to the heat sink.

If the machine is under warranty I would just try to get a new control board.

Thanks vette i tried your your high tech chop stick approach and found by prodding the black thing (see attachment) i could get the motor to kick in and out, so i took out the circuit board and re-soldered the terminals underneath the black charcoal looking thing! re-assembled and still got no joy, i could'nt see any more bulls-eyes "tech term" so could'nt do much more
Anyhow i have ordered a new circuit board from "ark euro" £75 about a third of the price of the complete machine when i bought it
So at least with your help i pretty sure it is in the circuitry board, so a gret big thank you for your help, just a pity i could'nt have got out of a bit cheaper
Regards Max............

 

[Bluechip]

Max

I think you were close to fixing it. The black blob could well be a bridge rectifier, (often close to a transformer).

Bit along the lines of this,

http://www.rapidonline.com/Electron...-Diodes/4A-8A-In-line-bridge-rectifiers/29673

Type / rating numbers probably differ, but if you can get it to work if you wiggle the thing, you MAY have a hairline break in the PCB trace ( land pattern) near it. Have a good close look with a hand lens, while giving it a gentle wiggle. PCB traces often fail immediately adjacent to the solder pad where the component wires are connected.
You could also re-solder it anyway.

Dave BC

 

[black85vette]

Well, good to know where the problem is even if you can't resolve it. I have seen an ad somewhere for someone who has a setup to troubleshoot and repair these boards for a reasonable price. You might think about shipping the bad one off for repair and keep a spare. Not that they fail often, but it will ALWAYS be right in the middle of something urgent.

I have repaired 3 of these now and keep a spare set of transistors and rectifier block on hand. Those are the two most common failure components.