Coffee Makers

© 2006 Dr. Ray Franco, PhD., PE    r.a.franco@ieee.org



Case History: Exemplar Mr. Coffee, Drip, 4 Cup, Coffee Maker Purchased at Wal-Mart in 2006 for $19.94.

For Maximum Resolution, Click on the Body of the Picture.

Photo: Exemplar Mr. Coffee Model NLX5

Exemplar Mr. Coffee, Drip, 4-Cup, Coffee Maker ($19.94).

Photo External Components of Coffee Maker

External Components of a Drip Coffee Maker.

Photo: Location of Manufacturer's Data

The Manufacturer's Data is Stamped into the Bottom Plate of the Coffee Maker. Mr. Coffee is Owned by Sunbeam.

Photo: Manufacturer's Data

Manufacturer's Tag - Model NLX5, SN: X069SX
120 VAC, 600 Watts, UL Listed 668N.

Photo Water Reservoir

Water Leaves the Reservoir Through the One-Way Valve and Enters the Heating Tube. Boiling Bubbles Push the Water into the Brew Basket.

Photo: Brew Temperature

Brew Heating Tube Temperature: 242 °F. Warmer Heating Tube Temperature: 260-313 °F. Duty Cycle: ON = 10 sec.; OFF = 127 sec.

Photo: Internal Components

The Water in the Heating Tube Starts to Boil, and a Column of Water Rides Upward on Top of the Bubbles to the Brew Basket.

Photo: Clock/Timer

Bottom of Coffee Maker. The 12 VAC Transformer Supplies Power to the Clock/Timer, and the Relay Switches 120 VAC to the Heater Element.

Photo Thermal Compond

Thermal Transfer Compound is Used between the Warmer Plate and the Heater Element.

Photo: Heater Element

600 Watt Heater Element.

Photo: Front of Clock/Timer PCB

Front of Clock/Timer Printed Circuit Board.

Photo: Back of Clock/Timer PCB

Back of Clock/Timer Printed Circuit Board.

Photo: Heater Element Resistance

Measured Resistance of Heating Element: 24.4 Ω.
Using 24.4 Ohms, the Calculated Wattage is 590 Watts.

Photo: Melted Aluminum Heating Tube

Test with Thermostat and Cutoffs Removed. The Aluminum Heating Tube Melted and the Heating Element Opened before the Plastic Caught Fire.

Photo: Some Melted Plastic

Some Melting of Plastic, But the Heating Element Opened Before the Plastic Caught Fire.

Hot Spot on Steel Plate

Hot Spot on Bottom Steel Plate after Test with Thermostat and Cutoffs Removed.


Case History: Evidence Examination Case #: F06-026.

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Photo: Burnt Coffee Maker

Burnt Coffee Maker from Case # F06-026.

Photo: Model No.: NLX5

Mr. Coffee, Model No.: NLX5.

Photo: Comparison to Exemplar Coffee Maker

Comparison of Exemplar and Burnt Coffee Makers.
Mirror Images.

Photo: Heater Element Reistance

Both the Water Heating Tube and the Heater Element were Intact.
Measured Heater Element Resistance: 24.2 Ω.

Photo: Rubber O-Ring

Ruber O-Ring Still Intact.

Photo: Acring on Power Cord

Electrical Arcing (Copper Beads) was Present on the Stranded Wire Power Cord.


 

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