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RE: Kill-A-Watt Resurrecting

Original poster: "Mccauley, Daniel H by way of Terry Fritz <teslalist-at-qwest-dot-net>" <daniel.h.mccauley-at-lmco-dot-com>


Perhaps you could reverse engineer the entire device and post some
schematics so that all of us here on the group and bang our heads together
and come up with some sweet modifications.  I no longer have the few i had
and blew up (since I sent them back for refund), so I can't help you there.

Regarding calibration, how are they measuring current?  If it is a current
sense resistor, you can simply replace that resistor with a different value,
or if a small current donut, add more turns to the donut.

The Captain

 > Ok,
 > I figured it out :-)))
 > The Kill-A-Watt is calibrated at 110.0 VAC at 10.00 amps.  You need a
 > variac and an 11.00 Ohm 1100watt! resistor...  Then it is
 > just a matter of
 > saving those readings/calibrations permanently using the front panel
 > controls...  Beefing up the 5V supply inside it would
 > probably prevent the
 > whole darn problem in the first place.  Apparently, it can
 > just as easily
 > be calibrated at 220VAC too...  Here is the exciting
 > test/calibration set
 > up :o)))
 > http://hot-streamer-dot-com/temp/P5010042.jpg
 > Hopefully, minor modification to a new unit will render it
 > "Tesla coil
 > proof" so it will not flake out.  I am not sure the meter is
 > real well
 > protected against accidental re-calibration =:o  Probably
 > best not to go
 > pushing buttons....  Easy to see how wild voltage fluctuations and
 > transients may hit on the calibration code stuff and mess it up...
 > Maybe time to fire off a letter to Prodigit asking for the "real"
 > calibration procedures in trade for how to harden it against "us" ;-))
 > Hehehehe
 > My meter is pretty torn up at this point, but it is spewing
 > its secrets all
 > over the place ;-)) I don't have a good current load so it is reading
 > currents like "P4.99" and stuff :o))  I can calibrate the
 > frequency to
 > 33Hz...  Stay tuned...
 > Cheers,
 > 	Terry
 > -----------------
 > Hi All,
 > I have now replaced all the silicon and individually tested
 > all of the
 > front board components on my killed Kill-A-Watt (kKAW :o)).
 > Replacing the
 > LM2902 "seemed" to help many things and all the other components were
 > fine.  I am not certain the LM2902 was really bad.  It got ripped out
 > before too much testing was done ;-))
 > I now think that the internal "big" IC (Prodigit 53920005) is a soft
 > calibrate chip.  It has it's own internal "nonvolatile"
 > memory.  I guess I
 > violated it ;-))  I note the display PC board has a jumper
 > that sure looks
 > like it may have has something to do with calibration or
 > testing.  It looks
 > like it was soldered by hand after the fact.
 > While a few of the front end components were out, the "Hz"
 > display read
 > "dc" so this ain't no dumb meter ;-))
 > Here is where the fun begins...
 > If you push both the "volt" and "Hz"buttons at the same time
 > you get "open"!
 > Then push "Watt" and get "C110".  Push "Watt" again and get
 > "C220".  Push"Watt" again and you get a flashing (probably test) full
 > display...
 > Or, if after step 1, you push "amp" you get "save"!!
 > Since this meter is supposed to be a 0.2% deal, I can only
 > assume that the
 > critical volts and amps calibrations are soft programmed into
 > memory.  All
 > the other displays are just hard digital calculations off
 > that.  I would
 > guess they just plug in a magic load and a person that knows
 > the right
 > buttons programs the calibration right off the front panel.
 > C110/C220 could mean "110 volt" or "220 volt" or they could
 > be voltage and
 > current cal...
 > Note this interesting photo of the front panel PC board under
 > the buttons:
 > http://cafeelectric-dot-com/killawatt/photos/IM0004.jpg
 > "menu", "up", "down", "enter", "output"....
 > So it is like one of those evil little Chinese puzzles as to
 > how to restore
 > the calibration...
 > So I'll goof with it and see if I can affect the
 > calibration...  If its
 > calibration can be reset, we are home free ;-))  But this
 > also indicated
 > that the big chip may have gotten bad signals that should not
 > be too hard
 > to clamp or filter...
 > Oh yeah!!!!!!!  I can set the "volts" to read 220 or 110 now >:o)))))
 > I don't recommend anyone with these meters going and pushing
 > these "magic"
 > buttons...  You may mess it up...
 > Possibly the PC board jumper is a hard program vs temporary
 > program thing
 > since the "new" calibration is lost if the meter is unplugged
 > right now
 > with the jumper in...
 > Hmmmmmmmmmmmmmmm.....
 > Cheers,
 > 	Terry
 > -----------------------------
 > Hi All,
 > Last Sunday I blew my Kill-A-Watt meter playing with my coil.
 >  I am not
 > sure when it went (too dark).  Grounding was poor and we were
 > sticking it
 > all around the systems AC wiring.  We were bypassing filters and such
 > trying to track down what turned out to be a MOV problem.
 > It was pretty messed up.  Drifting, big currents with nothing
 > connected,
 > voltage and frequency readings randomly off.  Nothing inside
 > was obviously
 > burnt up.  It appeared that the basic logic worked, it was
 > just that the
 > input metering was bad.
 > I replaced the LM2902 with a LM324 (fast Radio Shack
 > replacement).  That
 > fixed a lot of the trouble.  The drift and offsets are gone
 > now and the
 > frequency reads right again.  The only problem now is that
 > the voltage
 > reads 60% high and the current is 23% low.  I think the LM324
 > is "close
 > enough" to the LM2902 so that should not be the problem (but
 > it is only
 > running on 5V in this design)?  I had already ordered parts
 > from Digikey
 > before I knew I needed some more LM2902's...
 > I am going to try desoldering and carefully testing the input parts
 > next.  Maybe a bad part in there I am not seeing.  Hopefully
 > I can get it
 > going again since the problems don't seem unfixable.   I did
 > order up two
 > new meters just in case ;-))
 > So I guess even the latest ones can be damaged by Tesla
 > coils.  But this
 > kind of damage my be eliminated if I can find out "why" and
 > add a few extra
 > protection components.  Stay tuned...
 > Cheers,
 > 	Terry