Kenmore Elite Model 790 (790.42800500) Induction Cooktop circa 2006 - Error 32

My wife and I noticed over the past couple months that every so often when turning on PowerBoost setting for the cooktop the power to the unit would start to flicker and with all the burner LED status lights flicking on and beeping, followed by a "32" in the timer window and a power off.  Not good.  We love the induction cooktop and weren't ready to give up on it.

A quick lookup at http://www.searspartsdirect.com/cooktop-repair/error-codes/kenmore-790-mode-linduction-cooktop-error-codes.html says "low voltage output from the 12 volt power supply on the filter control board".    A look at the Q&A for the model shows some other people have had this problem too..http://www.searspartsdirect.com/model-number/79042800500/0583/0121040.html?searchType=modelSearch&q=790.42800500&searchTerm=790.42800500 (this one has some decent diagrams).  The suggested replacement is a $533 filter control board, http://www.searspartsdirect.com/part-number/5304454971/0022/628.html?pathTaken=partSearch.   With this being about half-the cost of a new unit and nothing to lose, we decided to tear into it Christmas eve after lunch.

The tool set to tackle this one.

We were smart when we installed the thing 8 years ago that we just put some high-density polyurethane foam tape around the edge to seat it onto the counter (marble tile) with no adhesive.  After shutting off the breaker and disconnecting the pigtail whip, I used a tile/glass lifter to gently pull up at one corner and "break the seal" of it having sat in the counter opening for 8 years.  Once it was loose, I attached a second lifter and moved it over onto the island next to the opening.

It's not immediately clear the best way to get into this thing, but I have to admit that it is made to work on.  With the unit glass side down, open the wire connection cover and disconnect the wires and the the black cable hold.  At this point you can also remove the bus bar jumpers (copper) and all screws and set aside.

Next remove the black vent cover on the front edge and the sheet metal screws around the perimeter (10 or so) once you have them all out, the galvanized steel rear cover should lift off easily with the wires and pigtail still attached.  Gently remove the three soft fiberglass insulation pieces and the fiber board piece covering the electronics region and set these aside so they are not damaged.

Holding both the glass and aluminum inner section flip the entire unit over so it is glass side up.  Now gently lift the glass piece straight off (it is not adhered, yeah!).  This exposes the induction coils.

The induction coils.

The front button control board can be removed by sliding off the X5 connector, and the coils detached by unscrewing the leads and unplugging the temperature sensor wires.  Once the coils are removed, gently lift off the fiber insulation blanket.

Remove the screws attaching the aluminum support plate to the electronics case underneath.

The electronics guts.  The Range Noise Filter board is at top right.

Looking at the filter board, my wife immediately noticed "one of these things is not like the other"... One capacitor can was cracked open and showed some corrosion, I noticed a second that was bulged on the top.  These were either side (top and bottom) of the filter torroid in the upper left.

After removing all the wires connected to the board, there are two tangs on the left edge to release the board, lift it up, and slide it out of the rear screw connections.  (You did remove all the screws, didn't you).

I took the board to the bench and after a trip to the local Radio Shack, had two new capacitors at a whopping $1.50 each.  These can be removed from the board with a low wattage soldering iron, and alternately heating one lead and wiggling the capacitor away from the heated lead to "walk it out" of the board.  Once removed, use some de-soldering wick to suck up the old solder and open the holes for the new ones.

Place the new caps, getting the polarity correct!, the board is marked with a "+" and the caps with a 

"-".  Solder them in and reassemble the cooktop.

We noticed too that some of the induction coil lead fork connectors were splayed from over tightening in the factory.  These were straightened before reassembly.  Make sure all coil connections are a tight snug, but not overly so.

Put everything back in the reverse order of disassembly, turn on the breaker, and test it out with a pan of water and PowerBoost.  No more error "32".  About 3.5 hours including a run into Radio Shack for the capacitors, and $3 in parts.  Maybe $35 in tools if you don't have a soldering iron and de-solder wick.

Tachometer needle gone haywire

After several instances of the tachometer on my New Holland TC29DA reading all sorts of strange numbers, I discovered the plastic barrel backing that presses onto the tach shaft was split open.  The plastic is so darn small and thin, a glue-job to reassemble it was unsuccessful.

The whole instrument cluster comes out with two Philips screws, detach the multi-pin connector from the rear, and take in the gauge cluster to the bench.   Remove the Philips screws around the perimeter and separate the cover glass and bezel from the gauges.  Slide off the old needle (mine literally fell off when the gauge was inverted) and grind or sand the old plastic barrel flush.

I prepped a new backing with a 4mm wide brass strip and 2mm OD x 0.45mm wall tubing (about $6 from a local hobby store) that was soldered together to form a new base and barrel to attach to the tach shaft.  Epoxy the new brass base onto the needle and let it cure.  With a pair of diagonal cutters, put a slight crimp in the tube to give it a light press-fit onto the 1mm tach shaft.  BEFORE, you push it on, go back to the tractor and connect the instrument cluster, and turn on the ignition (without starting), this will set the tach shaft at 0 RPM.  Align the needle and press it on.

Turn off the ignition.  Disconnect the the gauge, and reassemble the cluster housing, bezel, and cover glass.  make sure the needle doesn't fall low and end up below the stop inside the bezel.  Put it all back together, turn on the ignition and the tach should come to 0, start the engine and set to idle and it should be at about 600 RPM.

Beats $670 for a whole new instrument cluster... NH doesn't sell just a replacement needle.... go figure.

New brass coupling fabricated out of some 4mm wide brass strip
 and 2mmODx0.45mm wall tubing