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      Webinar Recordings Index Page   10/03/2017

      On-demand appliance repair training videos for Professional Appliantologist members Over 30 hours (and growing!) of original, high quality appliance training webinars developed and given by yours truly are at your fingertips, on topics you won't find anywhere else. Fill in those knowledge gaps, strengthen those areas of uncertainty, and boost your skills. Watch on mobile or desktop at your convenience whenever, wherever.  Ultra Short Primer on Basic Electricity, Circuits, Ohm's Law, and Schematic Reading (Length: 1:04:48) Basic Refrigerator Troubleshooting (Length: 1:10:45) Schematic Reading Workshop, 10/2015 (Length 1:19:08) Troubleshooting Strategies for Computer-Controlled Appliances (Length: 48:34) Semiconductors and PN Junctions (Length: 1:04:37) Appliance Temperature Sensing Devices & Technology (Length: 1:27:33) Voltage Measurements, Meters, Ghost Voltages, and Triac-controlled Neutrals (Length: 1:29:32) Troubleshooting with Tech Sheets, Part 1, 4/2016 (Length: 1:09:26) Troubleshooting with Tech Sheets, Part 2, 4/2016 (Length: 1:21:11) Tech Sheet Review, 4/9/2016: Bosch Speed Cooker, Amana Refrigerator, GE Glass Cooktop Range (Length: 1:22:58) Pulse Width Modulated (PWM) Switches used in Samsung Switched Mode Power Supplies (SMPS) (Length: 27:07) PWM Computer Cooling Fan in a Whirlpool Refrigerator (Length: 14:53) Understanding AC Split-phase Household Power Supplies (Length: 52:41) Troubleshooting a Samsung Electric Dryer without Disassembly using Live Tests and the Schematic (Length: 22:47) Troubleshooting a Bosch Dishwasher No-Heat Problem using the Schematic and Live Tests (Length: 15:38) Linear Motors and Linear Compressors (Length: 55:54) Bi-directional PSC Drive Motor Systems in Whirlpool VM Washers (Length: 56:52) Appliance Service Call Structure and Troubleshooting Strategies (Length: 1:00:16) The Ten Step Troubleshooting Tango and Workshop Exercises (Length: 1:35:39) Troubleshooting Ten-Step Tango Advanced Workshop (Length: 1:32:06) Ten-Step Tango Troubleshooting Workshop: Refrigerators (Length: 1:35:57) Whirlpool Duet Washer Schematic Analysis & Whirlpool Dryer Moisture Sensor System (Length: 1:03:04) Neutral Vs. Ground, Inverter Microwave, Digital Communications, Loading Down in DC loads, and more! (Length: 1:14:45) Gas Oven Service Call After a Parts Changing Monkey (Length: 36:04) AFCI and GFCI Circuit Protection Technology (Length: 41:26) Troubleshooting Samsung Refrigerators and more (Length: 1:29:58) 3-way Valves and Dual Evaporator Refrigerators (Length: 1:15:45) Split-Phase Compressors and PTC Start Devices (Length: 1:11:57) Gas Dryer Ignition Systems (Length: 53:50) Refrigerator Sealed System Thermodynamics, Part 1 (Length: 43:07) Refrigerator Sealed System Thermodynamics, Part 2 (Length 1:09:09) To access these webinars and all the other info-goodies here at Appliantology, become a Professional Appliantologist today. If you need cost-effective, time-flexible, state-of-the-art appliance technical training, check out the Master Samurai Tech Academy.
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      [Webinar] Samurai's Sealed System Sleuthing Secrets - 10/30/2017 @7PM ET   10/19/2017

      Having laid some theoretical groundwork in the last webinar, we're going to focus on practical considerations in this one. That means quick n’ dirty techniques for diagnosing sealed system problem using strategically chosen and skillfully interpreted temperature measurements.  Review homework from the first session on 10-2-2017. Home refrigerator practical design and operating rules-of-thumb useful for troubleshooting Practical application exercises Troubleshooting scenario exercise Techniques for making system temperature measurements for determining superheat and subcooling Sealed system diagnosis homework assignment (to be reviewed in the next webinar in this series) If you attended the first webinar in this series, this is your payday! We’re going to apply that keen, penetrating insight you now possess into money- and time-saving shortcuts you can use to diagnose real-world refrigeration systems on service calls. See this calendar event for more details                   

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LI-NY Tech

Miele produces the best dishwashers on the market today. They are high end machines...very quiet, they wash well and last many years beyond the life span of a lesser quality brand. However, like all machines they do break down. One of the most common failures to occur on a Miele dishwasher is the Water Proof System (WPS). That's that mysterious grey box under your sink. What is that thing?

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The WPS is a dual water inlet valve. The redundancy ensures that if one valve fails to close the other will, greatly reducing the chance of flooding your kitchen. That brass part on the left attaches to the house plumbing, the box contains the two solenoids and the gray tube contains the water intake hose, the wiring and outer sleeve. When the electronic calls for water the solenoids open and the water flows through the intake hose and into the dishwasher.

The outer sleeve acts a protection against leaks. If the solenoids leak the water will flow along the outer sleeve and into the drip tray in the base of the dishwasher. When enough water accumulates the float switch will be activated and the water intake will stop. The drain pump will also be activated until the machine is unplugged or the water is no longer present in the drip tray.

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The inlet to the WPS contains a filter and a restrictor. The filter stops large debris from entering the system and the restrictor ensures correct water pressure. The filters often get clogged and can be easily cleaned.

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The Miele dishwasher service manual states:

The WaterProof System (WPS) consists of a number of interdependent safety features to provide protection against water leakage.

1. Protection against solenoid valve leakage: Each water intake is controlled by an inlet valve. If this valve cannot close properly due to some defect or blockage by a foreign object, a second inlet valve ensures that the water supply is shut off.

2. Protection against water intake hose leakage: If a leakage occurs, water flows along an outer hose sleeve surrounding the intake hose to the drip pan. Here a float switch then acts to switch off a microswitch which closes the inlet valves to cut off the water supply.

3. Protection against dishwasher overflow: If some defect has caused the water level in the appliance to rise so that it overflows into the drip pan, and the water quantity sensor has also failed, the float switch is activated. This switches off a microswitch which closes the inlet valves to cut off the water supply. At the same time the drain pump is activated.

4. Protection against drain pump failure or blocked drain path: In this case the water level in the appliance rises until it overflows into the drip pan where the float switch is activated. This switches off a microswitch which closes the inlet valves to cut off the water supply.

Thanks for reading.

David

RD Appliance Service, Corp.

http://www.rdapplianceservice.com

RD Appliance Blog

LI-NY Tech

Recently RD Appliance Service was briefly confounded by a Miele washer, a W1918, not exactly the latest model. The complaint was that the washer would not spin out the clothing at the end of the cycle, it would leave them sopping wet. Sometimes, if the customer re-ran the cycle the washer would spin. So, armed with all of the necessary technical documentation and diagnostic equipment I ventured out to the home.

Upon arrival I opened up the service manual on my tablet, placed the machine into service mode and proceeded to run a spin test. The tub spun up to high speed without a hiccup. Hmmm, I thought. So I exited service mode and just ran a regular spin cycle, and again the washer spun.

After questioning the customer about her use of the machine I concluded that the machine was sometimes being overloaded and that this was causing it to be unable to balance itself, thus preventing it from spinning.

Not so.

She called back the next day with the same problem, and again when I arrived the problem would not occur. So I needed to do some more in depth research on this issue as this is no “Just replace it” type of washer, they retail for $2000 or more. With some helpful tips from my fellow appliance technicians at appliantology.org I returned armed with more knowledge and we got it figured it.

My father and I both went back on this, two heads and all. I called the customer about an hour before we were going to arrive and had her start a wash cycle. This worked out well because we arrived just at the end of the cycle and found the washer not spinning. Finally! No spin at the end of a regular cycle, no error codes flashing. Set it to a spin only cycle, no spin. Put it in test mode and ran a spin test, no spin. Alright, now we’re getting somewhere.

So, we opened up the front of the machine (thank you Miele for making the whole front panel open on a hinge!) in order to find out if the motor was getting voltage, which would indicate a problem with the motor itself. However, this old Miele technical info does not include voltages for the motor, and the wires are all the same color and not labeled, same goes for the connectors. We knew it uses a single winding DC motor, but that’s about as in depth as Miele gets regarding the motor. So after exercising our finely honed diagnostic skills we determined which two wires were the motor voltage supply wires and we attached the voltmeter leads to them near the lower electronic (secondary control board).

We once again put the machine into spin and the damn thing started spinning again. This, however, showed us the voltage used by the motor when it is working, and this is crucial information. In case you are interested it uses ~16-20 VDC on tumble, changing polarity as it switches directions, then the voltage ramps up to a whopping 195 VDC on max spin.

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Ok, so we know the motor works, but we still don’t know what’s wrong with the washer. We began doing basic diagnostic checks once again, check and clear drain pump trap, check pressure switch hose, etc. Nothing. So we ran another test cycle. This time allowing it to fill and tumble and then move to drain and spin. Aha! Now it won’t spin. It tumbles a little at 16-20 VDC, then stops and won’t spin, no voltage to the motor. Ok, good. I suggest checking the pressure switch again. So my father tapped the pressure switch and voila!, this motherfu%&er starts spinning, and reads all the way up to 195 VDC again. Yes! The pressure switch was sticking….sometimes.

So, we’ve replaced the pressure switch and the air trap with the pressure switch hose and that old school, quality German washing machine is running like new once again.

Thanks for reading.

David

RD Appliance Service, Corp.

http://www.rdapplianceservice.com

RD Appliance Blog

LI-NY Tech

Centrifugal Pumps and Cavitation

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I recently had a customer whose washing machine would not drain. I attributed this problem to the excess of suds in the tub. The customer seemed skeptical of this diagnosis and so this problem seemed like a good topic to delve further into.

Oversudsing issues are very common in washing machines and dishwashers. Using the incorrect type, or an excess, of detergent can cause an oversuds situation. This often leads to drainage problems. The drain pump cannot pump out overly sudsy water. But why not? It's because of something called cavitation.

Cavitation is the formation of vapor cavities in a liquid. Washing machines and dishwashers use centrifugal pumps. A centrifugal pump needs an uninterrupted supply of water to function properly. The spinning impeller causes the water inside the pump to spin as well, creating centrifugal force, which causes the water to flow away from the center, or inlet, of the pump and out of the discharge port. This displacement creates negative pressure which sucks more water into the pump. Introduction of suds, which are mostly air, into a spinning impeller will interrupt the flow of water and introduce air into the system, disrupting the vacuum being created, and ultimately preventing the pump from being able to discharge the water. This will not be resolved until the suds are eliminated. Fabric softener or vegetable oil can be added to the machine to help to eliminate the suds and allow the pump to finish draining the water.

The video below is a brief introduction to the way in which centrifugal pumps function.

Thanks for reading.

David

RD Appliance Service, Corp.

http://www.rdapplianceservice.com

RD Appliance Blog

LI-NY Tech

IR Thermometers and Emissivity

"Emissivity is the measure of an object's ability to emit infrared energy. Emitted energy indicates the temperature of the object." That definition is from an article on Rayteks website titled Emissivity of Most Common Material. I only recently learned what emissivity meant, and because of that I've been using an infrared (IR) thermometer for over a decade and it seems that only now am I able to use it properly.

IR thermometers measure surface temperature, not air temperature, and so it is important to know both the emissivity value (EV) of the material you are measuring and the emissivity setting (ES) on your IR thermometer. Some IR thermometers have a programmable ES, for instance the Fluke 62 Max, which is adjustable between 0.1 and 1.0. Others have preset ES, usually at 0.95. An EV of 1.0 means the material gives off no radiation, this is known as a "black body". The lower the number the more radiation the material emits, and the materials with EV of 0.99 and below are known as "gray bodies". Wood, for instance, has an EV, depending on species, of between .88 and .96. Polished aluminum, on the other hand, has an EV of 0.04 - 0.05.

To better understand what this means in practical terms I performed a simple experiment. I set my oven to 350ºF. I used a Fluke 62 Max to take measurements at the back wall of the oven after it was preheated. I did this three times for each ES, in increments of 0.1, from 0.9 to 0.2, and averaged the three readings. Below is a graph of the results.

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The graph above shows that at the highest ES the readings were quite accurate, and this makes sense because the EV of steel is 0.8-0.9. But by 0.3 the temperature readings were off by almost 400ºF. And at a setting of 0.2 the thermometer was incapable of reading anything because it surpassed the maximum readable temperature of the 62 Max, which is 932ºF, almost 600º higher than the actual temperature.

It's easy to see how using an incorrect setting could give a very inaccurate reading and how important it can be to align your thermometers ES with the actual EV of the material you are measuring. In many cases the default ES of 0.95 will be suitable as most materials appliance techs are working with, plastic and steel, have an EV of between 0.85 and 0.95 anyway, so it will get you pretty close. But other materials we encounter, such as aluminum, brass and copper have much lower EV and an ES of 0.95 will not garner accurate measurements.

Further Reading

- Emissivity Coefficients of Some Common Materials

- IR Education: Emissivity

- The Principles of Noncontact Temperature Measurement (PDF)

Thanks for reading.

David

RD Appliance Service, Corp.

http://www.rdapplianceservice.com

RD Appliance Blog