I have 4 SmoothSteppers on machines and have not suffered from noise issues on three but the Beaver Mill would have problems in two distinct areas.
1. If the E-Stop button was pressed on my control panel then 90% of the time the SS would hang and I would need to restart Mach. My E-Stop not only sends a signal to Mach but also drops out all the contactors on my mill so things like AC power to the servo drives get cut.
2. If sitting for extended periods with Reset flashing the SS could hang.

I read with interest this thread and also the discussion on the Yahoo group http://www.machsupport.com/forum/index.php/topic,16186.10.html

I decided I would remove the capacitor and resistor that are on the SmoothStepper at the side of the USB socket, they are C4 and R5 and since removing them I have tried hard to make the SS hang by repeatedly pressing the E-Stop button and also have left Mach sitting for long periods with the rest flashing. I have not had a single hang and its now been 5 days of trying.

So it might be well worth users that have issues trying this. Its quite easy to remove the capacitir and resistor if you have two soldering irons, you just melt the solder at either side and then lift off with the irons. I actually just used one but had to go from side to side quite a few times easing the cap up slightly each time and after a while it came off. I also tried crushing the components with needle nosed pliers on a spare SS I had and this too was easy and worked well but I would recommend desoldering rather than crushing, I just did it that way as a test to see if it could be easily done. Greg has also mentioned another way, if your soldering iron can bridge the ends of the component you can drop a blob of solder on the top to bridge the component and this will then melt the solder pads and allow you to lift it off with tweezers.

So although my problem was not a serious one as it only ever happened at an E-Stop or whilst sitting doing nothing, I still want to thank David for his testing and findings as they have cured a minor niggle that I had.

Hood

I put together a quick PDF a few days ago that details this modification. You can download it here: http://www.soigeneris.com/document/smoothstepper_board_modification.pdf .

If you are dropping the contactors it maybe an idea to
place a varistor across the coil.This will contain the voltage spike
from the deenergizing coil.

If you are dropping the contactors it maybe an idea to
place a varistor across the coil.This will contain the voltage spike
from the deenergizing coil.

They have snubbers ( or whatever they are called) already.

Hood

Thanks Hood and Jeff for sharing your findings and solutions.  Jeff's solution of cutting the trace is a fine one.  Just beware that the ground plane is close to the surface (about 0.0073 inches below), and that if you cut into it there is a chance that you could short the outer trace to the ground plane and you won't accomplish anything.  I don't want to make it sound like cutting the trace is risky, but I just want to point out something you might not be aware of.  Like Jeff suggests, use an ohm meter to make sure the connection has been severed.  To see if the shield was accidentally connected to the ground plane, ohm from the outer shell of the USB connector to the ground of the board.  You can find ground on the external 5V connector or pin 5 of port 3 (green screw terminals).  The distance from the ground plane to the power plane is huge, so there is no worry about shorting the ground plane to the power plane unless you really dig deep!  The distance is about 0.039 inches.

For those of you that would prefer to desolder the components, I took a before and after shot of that area of the board:

Before:



After:


Thanks,

Greg

Hi,

To desolder the components R5 and C4, lay the tip of the soldering iron along side R4 (in between R4 and C5 is best).  Most iron tips will be large enough to bridge both ends of the component.  If not, alternate the tip back and forth between both ends in a rocking motion. If necessary you can also add some solder to help it reflow.

When you see that both ends are molten, wipe the component off the board with the iron.

Then do the same for C5. Note the capacitor will take a little longer, but the process is the same.

A lot of people think that you need a really fine tipped iron for SMT work. The problem with a really fine tip is that the heat gets sucked out of it too easily.

For most of my work I use a 1/8" chisel tip.

Cheers,

Peter.

I have a new Smooth stepper that I received last week and the "offending" components have been omitted from the new ones.
Don

Yes Greg said he was going to remove them on any he sent out and on the new batch they wouldnt be soldered on.

Hood

When I first installed a SS I had hangups every time I started my VFD.  I fixed this  by making some alterations to my grounding system.

This involved bringing computer and VFD ground to a common point.

Out of curiosity I removed the before mentioned resistor and capacitor and reverted my grounding system to what it was when it used to hang.

I could not get it to fail.  Seems this fix was enough to rectify my original issue.

Greg

Is removing these two components effectively the same as removing the ground shield on the USB cable going into the SS as discussed originally on the Yahoo group?

Tom