Re: cap didn't pop

Dave,

I think you are correct; the drive is toast if the .05 ohm resistors
blew. What probably happened is when the cap spewed, the electrolyte
shorted out the ciruitry and turned all the MOSFETs on
simultaneously. The rest is as they say, history.

I would like to see the drive. Put a note in along with it and I will
see what I can do.

Mariss

--- In CAD_CAM_EDM_DRO@y..., "turbulatordude" <davemucha@j...> wrote:
> 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)