It take's a lickin' and keeps on tickin' !

[Kev Williams]

Many of you may be too young to remember the old Timex watch tagline --

Just gotta say, Timex has nothing on my Gravo LS900...

The controller went out a few weeks ago, had Gravograph repair it, cost under $400. The X driver was bad.

Just before it went bad, the X axis developed a loud high pitched whine when traveling fast. When I got the controller back, the whine got louder. I've been assuming either one of the support bearings or stepper bearings was the source of the noise. Tonight I decided I should pull apart the stepper assembly and see what's going on.

Imagine my surprise when I pulled off this cap (for the first time ever), and found this going on, which may explain the driver going bad:

A bit out of focus, sorry--
This plug feeds the stepper, it was pretty much welded shut, so I had to break it apart with some needlenose pliers
xs1.jpg

the end wire is missing insulation on the incoming plug,
xs2.jpg

and the lower wire's not even connected to the outgoing plug!
However, I may have done that while pulling the wiring up thru the hole--
xs3.jpg

-or not! This is the lower connector post, been just a bit hot...
xs4.jpg

And the quickie repair job-- I broke away more of the burnt plastic, re-soldered the upper bad end to the post,
soldered an extension onto what was left of the lower wires, and used the last of my heat-shrink on it.
I cleaned up the burnt post and soldered it to the extension, then plugged them together.
Go ahead and laugh at the tape, it's better since I took the pic
wires 1&2 plugged back in, wire 3's lower post was still encased in plastic, the other end was a victim of broke plastic,
but they plugged together fine...
xs5.jpg
I taped up the plug and the extension connection, tucked it all back in the can, and voila! Runs great and nearly all the high pitched racket is gone!

The funny thing is, aside from the extra noise the machine has been working just fine, just keeps on tickin'! How or why I have no clue!

So I'll be ordering up some new plugs & wires and using it as-is till I get them. Meanwhile, still in service makin' me money...

[Frederick Skelly]

Glad everything turned out ok! So what do you think was causing the whine - one of those loose parts rubbing against something else?

[Kev Williams]

I don't understand how steppers work exactly to be honest-- Not positive but pretty sure the bad wire was the ground wire, and the stepper was using one of the other wires as it's ground connection, or itself as attached to the machine. Whatever was going on, it seems it was fighting itself, even at rest, as the X stepper has been much hotter to the touch than the Y for some time now. After the fix, they're both pretty equal.

It's still a bit noisy, and since it's going on 15 years old a new stepper and bearings are probably needed too