Re: cap didn't pop

Yikes, I got some work to do.

The 470Uf cap blew and sprayed the big 68,000 cap and the rectifier
diodes and the back of the enclosure.

The 201 is smoke. seems upon further inspection, the 0.05 ohm
resistor next to the pot is fried and the other one broke in half
lengthwise. seems I didn't see that part until I found the half that
fell off.

Since parts of the 201 are missing, I have no reservations in stating
that it is gone.

Since I am sure I didn't reverse the cap, maybe I didn't get that
loud pop one might expect.

I did blow the 6 amp fuse between the 201 and the power supply AND
the 20 amp one on the 110 line.

The stepper is fine. Of course the cheap stuff always survives.
Some corolary of Murphey's law I'm sure. The extent of the damage is
inversly porportional to the cost of the components or something.

I tested everything and put in another 201 and ran at slow
aceleration and peaked at 3,000 hz and it all seems to be running
fine.

It's late and I'll do the clean up in the morning. I wiped
everything down that was easy. Now I think dissasembly is in order.

In the second attempt, I found that the leadscrew was off alignment
near the end so the gearing started binding up and that was what was
stalling the stepper.

Would the 36 feet of 18 ga. have any effect on the system ?

Also, the picture (photo's section folder in Daves unit) shows all
black next to the resistor and pot. there are no parts left on that
part of the board. the large cap is dirty from the other resistor
letting go.

BTW, do you like to have these blown units back for your review ? I
know you have a great track record and have categories in which you
have records of failures.

Dave

--- In CAD_CAM_EDM_DRO@y..., "mariss92705" <mariss92705@y...> wrote:
> Dave,
>
> The stuff is corrosive and electrially conductive. Here's the hi-
tech
> way of cleaning it up.
>
> Remove the board from the mounting plate and wipe off the heatsink
> compound from the MOSFETs (it's messy). Clean the plate thoroughly
> using a solvent like MEK or acetone.
>
> Get a hairdryer, a cardboard box(6" by 8" by 6"), an old toothbrush
> and liquid soap (dishwashing soap). Turn the faucet to hot water,
> pour a little soap on the board and start scrubbing it under the
> faucet like there's no tommorow. Rinse very thorougly and repeat if
> necessary.
>
> After you are done, shake the board dry (or use compressed air).
Put
> the board in the box and close it, insert the hairdryer nozzle
> between the box flaps and turn it on at a low setting. Go away for
10
> minutes and think about how bad it is to reverse polarity on a cap.
>
> When you return, turn off the hairdryer and remove the board. Re-
> grease the MOSFETs and mount it back on the plate. Cross your
fingers
> and turn on the power. If the drive has not been damaged, it should
> take off OK.
>
> Mariss
>
> --- In CAD_CAM_EDM_DRO@y..., "turbulatordude" <davemucha@j...>
wrote:
> > Hi Marriss,
> >
> > I have to disagree with your statement that caps blows up with
the
> > sound of a firecracker. It was not too loud, and not too much
> > smoke. What scared me the most were the sparks from the 201.
> >
> > I just put together a huge power supply, 68,000 uF cap and a 10
amp
> > transformer, connected a 201 to a NEMA23, 6V, 0.85a stepper Vexta
> > stepper, and used a 6.19K ohm set resistor. ( talk about
overkill )
> >
> > I connected the PC's 5 volt to the #10 pin and used an aluminum
> > 470uF cap with about 18 inches of leads from the power supply to
> the
> > 201. I cut the 470's leads to about 1/2 inch. I had a 6 amp
fuse
> > (one of my many mistakes) in the +V line. I wish that blew
first,
> or
> > at all.
> >
> > I started testing the table with running 5 inch jogs on a 400
step
> > motor, with a 1/2-13 all thread rod.
> >
> > At 10,000 maximum steps, the motor started missing, although I
was
> > not sure if it was during acceleration or where it started.
> > Acceleration was 200 steps in TurboCNC.
> >
> > I reduced to 5,000 maximum steps/sec and it worked fine. I
> increased
> > to 8,000 and increased the acceleration to 2,000 and during the
> ramp
> > period, it started missing steps. I stopped the step command when
I
> > heard the missing, and shortly thereafter heard the first pop.
> >
> > I turned off the 110 to the transformer, but have no fast dump
for
> > the cap. Since I do not have any drain on the 68kuF cap, it
keeps
> on
> > going... and going... and going...
> >
> > I looked at the 201 and within a second I could see the sparks as
> it
> > was releasing all kinds of magic smoke.
> >
> > At that time I was pulling the wall plug.
> >
> > With some quick overview, the major destruction was the
> catastrophic
> > freeing of electrons in such a way that all components that used
to
> > occupy the space between the pot and the angled resistor have
been
> > liberated and have joined Elvis in the hereafter.
> >
> > The pictures are not too good, but you might get the overall idea
> of
> > the location.
> >
> > Oddly enough, there was also some heat transfer grease liberated
> from
> > under the opposite corner, just under the #12 connection.
> >
> > I connected the stepper to the 201 with about 30 feet of #18ga
> wire,
> > that was coiled on the floor. That means there was 4 feet to the
> > stepper and 4 ft straight to the 201 and a sizeable coil on the
> floor.
> >
> > No e-stop.
> >
> > All that said, my questions now come towards not repeating the
> > performance and clean-up.
> >
> > #1) immediate handling, how aggressive is the fluid from the
> cap ?
> > do I need to scrub everything or just wipe down the stuff that is
> > easy to get to ?
> >
> > Now, the simple stuff, what else did I do wrong ?
> >
> > I put a photo in the photo's section under the Daves Unit folder.
> > (I web read, not e-mail, so I don't know how to attach a photo)
> >
> >
> > Dave
> > (again stepless in NJ)