Well, it would appear my Mantis is down and out for awhile! 
I was doing some test cutting with it – I seem to have the settings in Mach2 correctly adjusted and with a little Ports & Pins tinkering from JT, working predictably and repeatedly – last night when right in the middle of plunging the spindle into a copper PCB, everything just stopped. The 24VDC power supply to run the driver board and steppers was dead with now power LED on! 
At this point, let me take you back a couple of days prior to this event to give you a little history. Two nights ago, I was test jogging the Mantis around in Mach2 making sure everything was working fine – it was. I deactivated the steppers (hit the Reset e-stop button in Mach) but left the driver and PC powered while I was watching Hell’s Kitchen (yeah, I watch Hell’s Kitchen – sue me! lol). I started watching the evening news afterwards and fell asleep. needless to say, I woke up in the middle of the night and found that the Mantis and the PC were both off and would not come back on. I was too tired to figure out what had happened so I went to bed. The next morning, I checked around and found out that ALL of the AC outlets in my basement were out yet all the lights worked as did my TV. After getting home from work that night I did some poking around and found that the first AC outlet on that branch line out of the breaker panel is a Ground Fault Circuit Interruptor (GFCI) outlet. Thinking maybe it popped I tried resetting it. Nothing so I tired hitting the test button – nothing. It appeard like it wasn’t working. I’ve had these GFCI outlets go bad before so I suspected that was the case. I took the cover plate of f the GFCI outlet and did some testing with my multimeter and found that there was indeed 120VAC going into the GFCI but nothing out on the other end. So figuring that since this a new house (only two years old) it must be a bad GFCI outlet - I jumped out the outlet to reconnect the downstream outlets to the breaker panel. The next evening, I started doing the test cutting I mentioned above. So I unplugged and replugged the 24VDC power supply into the mains – nothing LED still out. I disconnected the Mantis from the parallel port and then replugged the power supply in and it worked! Hooorayyy! 
Well, don’t cheer yet. I then tried reconnecting the parallel port cable – I know I shouldn’t do this with the Mantis powered on but I figured the PC was powered off and I do have that cool printer port protector from Hubbard CNC installed – and got a big shock when the shield of the parallel port cable connector touched the connector on the Mantis board and the power supply LED went out again! Oh oh! I tried various spots on the power strip to plug in the power supply and nothing worked. So I then tried a totally different outlet and was able to get the power supply to stay on even after the Mantis and PC were powered back on. So I brought Mach2 back up and found that the x-axis and the z-axis worked fine but the y-axis was totally dead. I felt the heat sink over the Toshiba driver chips and it was scorching hot – I blew the y-axis driver chip! 
I unplugged the driver board and put a couple of fans on it to supplement the built-in fan and waited for it to cool down. I then plugged the driver board back in and without even energizing the steppers – it heated back up to flaming within a minute or two. So discussing it today with JT, I think it’s clear that I have a ground fault somewhere – perhaps an incorrectly wired outlet and that the reason the GFCI outlet wouldn’t reset was the ground fault was still there. One of the outlets on that branch did have a 1500W space heater (1500 watts is right on the edge in terms of amperage at 12.5 amps) plugged in – not sure if it was on to tell you the truth – so that could have been the problem if it overheated the outlet, particularly if the outlet was wired incorrectly. I put up sheet rock in the basement a few months ago and could have run a screw into one of the wires. That might explain why my PC has been systematically dying, component by component even though it’s only two years old.
So that’s where things stand right now – I have a blown driver chip and a ground fault problem somewhere in my basement. I do have an extra driver board AND an extra Toshiba driver chip I could use to repair or replace the existing Mantis board. I have to stop tonight at a Home Depot or Lowes to pickup an outlet tester and a couple of 20 amp outlets – the existing outlets are all 15 amp. It’s a bummer but it’s a lesson I think I won’t forget. I’ll keep you posted.
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Man, this thing’s a real pain, isn’t it. He’s finicky about every little thing.
Are you sure the circuit this guy is on is good for 20 amps? Wouldn’t be worth it, really, if it’s sitting on a 15 amp line out the breaker.
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@No One, Yes he is a real pain! lol This one was my fault really – ignoring a ground fault is a bad idea. No, it’s a 15 amp circuit to the breaker. I have since found that the GFCI outlet that branch is on was bad. I used an outlet checker and did not find a ground fault so I’m kind of stumped. Was it the bum GFCI? Was it an overheated outlet due to the space heater?
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As Forrest Gump said, “Stuff Happens”. This whole thing is a learning process, and Craig is probably saving a bunch of folks some serious aggravation. You never really know what is going to happen next.
My paper mache router (made from MDF) which had previously milled several Fabio PCBs and some Allegro stepper driver boards stiffened up when I moved it into the house for the winter. Both the X- and Z-axes became VERY hard to move. This caused the x-axis stepper to skip a pulse every once in a while (probably during a Rapid) so the resultant Fabio board has traces OK in the Y direction, but too skinny in the X direction with a few breaks (so it is no good). A test showed that the X-Z connector which is assembled from hard maple had shrunk in the cross-grain direction, squeezing the bronze bushings around the X and Z rods into ovals. This increased friction hugely and caused severe drag on the Steppers. It appears that the really low humidity inside during cold winter weather has caused enough of a dimensional shrinkage to bind the two axes.My temporary solution is to use a buffing wheel and polish the rods, and then use the rods themselves with buffing compound to re-shape the bronze bushings. During the next month, we’ll redesign the X-Z plate using humidity-insensitive materials (aluminum).
Meanwhile stay tuned to Craig’s Never-ending story.
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Craig Bickford Reply:
December 6th, 2010 at 2:10 pm
@JT, Thanks JT! It’s amazing how the things you don’t think of can come out of nowhere and bite you REAL hard. I think I have my home’s electrical problems worked out – at least in the basement anyway – so all I have to do is swap out the “junk” TB6560 driver board for the good one I have kicking around and I should be back in business. At least I HAD the Mantis jogging properly and repeatably engraving just before it blew up.
The Pats vs Jets tonight on Monday Night Football will keep me and most of the rest of America glued to the TV but I hope to be test engraving again tomorrow. Maybe I can work on it during the commercials. 
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No One Reply:
December 6th, 2010 at 6:27 pm
@Craig Bickford, You could just bring a TV into your basement! (Can you see how much I want one of these things? I have so many projects I want to work on with a mill.)
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Craig Bickford Reply:
December 7th, 2010 at 8:58 am
It’s funny that you should mention that but my basement is finished – my eldest daughter has a room down there, my computer and desk are down there, my workshop is down there, and our family room WITH TV is down there as well! I suppose I could have worked on the Mantis during commercials but in truth I was pretty wiped out anyway. So tonight, refreshed from a 45 to 3 spanking of the Jets by the Pats, I plan on restarting the Mantis and get it working so I can start cranking out some model railroad electronic kits, Fabio arduino clones, and David Carr’s stepper driver boards. I’m also working out all the details of putting together Mantis kits (probably partial Mantis kits) for sale too.
Wow! Maybe the ebay special Toshiba driver boards are too sensitive and not worth the little bit of cost savings you get when compared to other 3-axis drivers available. I think if I build the mantis I’ll go for another driver board thats a little more durable but the posts are fantastic and its nice to see someone complete the project and let the community know all about all the “gotchas” you encountered building it. Thanks!
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Craig Bickford Reply:
December 8th, 2010 at 1:19 pm
@zabbo245, Welcome zabbo!
Well, watch out – many of the boards out there like the Hobby CNC board use the very same Toshiba TB6560 chips which suffer from the same susceptibility to back EMF but perhaps those boards have some way of dealing with it. If you read some of the earlier Mantis posts – I got this board as a replacement for one I thought I had fried but as it turns out, haven’t. I got it for Hubbard CNC’s cost along with a replacement TB6560 chip so I really have two boards and one chip for a tad less then one, lets say Rockcliff Machine board. Plus, as it would seem, there is a lack of decent documentation anywhere and plenty of indifferent eBay sellers for the board so I view it as a service to the community at large to point out a good source (Hubbard CNC) and to try like heck to get this board to work in the Mantis application and work out all the “gotchas”. Thanks for commenting – keep checking back for updates!
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Thank you for posting such a good followup to designers posts on Mantis. Nice to see all the realword information you need to build one that he didnt mention. hope you work out the driver problem and can start making pc boards.
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thank you for the provide good information.
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Well I guess the Mantis is getting replaced by the bigger nand better FarbricationStation!
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