Samurai Appliance Repair Man

[Samurai Appliance Repair Man]

This is a great question, Soo. Good job for thinking about this.

Short answer: There’s more than one way to skin a cat.

Long answer: On service calls, you will have to make decisions about how to test your troubleshooting hypothesis based on the specifics of the situation and your experience with that particular appliance model.

This is a stack laundry unit with the motor and drum right near the area where I need to put my meter probes. I had to make a risk calculation: am I willing to have my hands and meter probes (with wires) near a running motor and rotating drum in a tight space with low visibility and a live circuit so I can make a voltage measurement? Or, in this particular situation, do I instead opt to unplug the unit and do a different measurement (ohms) on a dead circuit with nothing running?

Also, based on my experience with these dryers, I know that if the heating element tests good on ohms, there’s a very high chance that it’s functional under load because these elements do not fail that way– once they go open, they tend to stay open and one end of the broken heating coil fuses with the metal casing. So I knew from experience that an ohms test on this particular dryer model with this particular element type was diagnostically meaningful. But this is wisdom that comes from experience. I may not opt for an ohms test on another type of dryer with a different type of heating element.

In that video, I was also illustrating some basic circuit principles that you’ve learned such as total resistance in a series circuit with more than one load.

Finally I was illustrating how to apply the concept of EEPs to test your troubleshooting hypothesis.

Pop Quiz: What would be another way to troubleshoot this problem? What electrical measurement would you make and where?

[Samurai Appliance Repair Man]

but in general we need OHMS of the coils,

You do not need or care about the ohms of the motor coils. Ohms are only part of the story when it comes to total opposition to electron movement (current). This total opposition to current is called Impedance. Most of the coils opposition to electrons is from Reactance, specifically inductive reactance. This only appears when electrons are moving. Impedance is the vectorial sum of Resistance (ohms measurement) and Reactance.

Ohms measurements only measure the resistance of the copper windings to electrons. This is called Resistance. But Resistance is a minor part of the total Impedance. Most of a motor’s impedance is comprised of Reactance. So ohm measurements are only a tiny part of the Impedance story.

The Horsepower rating of a motor is referring to its mechanical output power. So you can’t use it to calculate the motor’s input wattage or amps because there are losses from input to output. So you need to supply more wattage on the input to get a specific horsepower on the output. The losses show up as heat losses from the motor itself. So ignore horsepower and use the other spec you’re given: FLA.

FLA is full load amps. Since this is an input to the motor, that is the expected amp reading on that motor when operating with a full mechanical load. No calculation required– just measure the amps to see if the motor is operating in spec or not.

Don’t jump down rabbit holes wondering about motor power factor and efficiency. You will never need to do this as an appliance tech. Instead, learn to interpret and apply to the specs that are already given to you. If you want to delve into PF and %eff out of curiosity, that’s great but they are not useful in troubleshooting which is why they are not taught in the course.

[Samurai Appliance Repair Man]

as regards checking the the motor’s amps are power factor and efficiency not supposed to be taken into account?

We don’t need the power factor because we’re not interested in the motor’s efficiency. As technicians, we are only interested in whether or not it is operating in spec. Specs must be given to us. What is the spec we need to know about a motor’s operation in order to assess whether or not it is operating in spec?

as iv been tought by you i tried to calculate the amps by using P/E or wattag by E*I AND the results didnt come out right as stated on this motor’s nameplate.

You’ll have to give a specific example and show your calculations.

[Samurai Appliance Repair Man]

On the third video shows Mr Brown checking digital communications pulses on the receive terminal.Where is the other meter lead located?

Since data is DC voltage (switched on and off at specific rates), the reference will be DC Ground (not chassis, not AC Neutral) as it would be for measuring any DC voltage.

[Samurai Appliance Repair Man]

half splitting a 240 volt heating element is always a live test.

You could half split using continuity testing but this is clumsy and unreliable. Using half-splitting with voltage tests is expeditious and very reliable. And to test for voltage, you have to be working on a live circuit.

[Samurai Appliance Repair Man]

i need to have the techsheet as well as the schematic

Exactly! Now you’re thinking like a tech. For any problem solving, you need to be able to identify what additional information you need to solve the problem. Sometimes, that’s a strategic electrical measurement, sometimes a temperature measurement, sometimes you need the schematic to see how the components get their power supply.

In the case of the Samsung board pinout shown at the time you called out, you need to realize that that diagram is simply telling you what those board pins connect to. But it doesn’t tell you how it connects. So, for example, CN4 & 5 are both labelled Fabric Temperature Sensor. Does this mean there are two sensors? Or does it mean that those pin are the two sides of the sensor circuit? The schematic would show explicitly how this circuit is configured.

This is the type of thinking a technician does every day, all day. It’s both understanding how circuits work AND the technology you’re dealing with. All mental cylinders firing at the same time as you bring your observation and analysis to bear on the problem.

[Samurai Appliance Repair Man]

Technically, the base frequency doesn’t change but instead is modulated by the duty cycle. But your meter picks up the change from 0 VDC to 12 VDC and from 12 VDC back to 0 VDC and then displays this to you as a “frequency.”

[Samurai Appliance Repair Man]

on the first video discussing thermal fuses and hi limit tstats at 16:00 minutes on the PCB pinouts ther are two lines spelling FABRIC DETECTION SENSOR are those the connections to the moisture sensor?
2.why there are 2 conecctions for TEMP SENSOR on pin 3 and pin 7 are they both connected to the same thermistor? or they are 2 separate thermistores for each pin?

I want to help step you through this so you get the thought to figure these kinds of things out.

You can easily answer this question by looking at another document that accompanies the pinout diagram for this model. What other document would you need to see?

3.as regards the moisture sensors on the 2nd video how can you actually test them ? is there any easy straightforwad and practical test for that?

Moisture sensors are just two metal bars set close together (but not touching) so that when wet clothes bridge the gap between them, it completes a circuit that the board is monitoring. They very rarely fail. But some self test modes in some dryers will let you test the sensors by showing you when the metal strips are electrically connected. If not, you can always use your meter set on ohms and probes on each wire from the each sensor bar and see if the reading goes low resistance when you bridge the bars with a wet cloth.

[Samurai Appliance Repair Man]

I use the term liability to mean that IF break or damage something on a service call, you are liable to fix or correct it. Anytime you move an appliance, you are incurring a risk of doing property damage. For example, you could scratch the kitchen floor when pulling out a dishwasher, range, or refrigerator.

In the specific case of dryers, we usually aren’t dealing with nice floors or cabinetry, so I’m mostly concerned about two things: 1) an impossible vent configuration in a laundry cubby where the only way to reconnect the vent is by removing the washer, too. And 2) gas lines that are too short or that use coiled copper where the copper tubing can get crimped. I’m always looking for ways to troubleshoot with minimal disassembly and appliance movement. Usually, that means accessing the control panel to troubleshoot from the control board or timer. You can usually access the control panel with minimal movement of the appliance.

When you do need to move the dryer to complete the repair, be sure you have evaluated the two items above to both plan for the movement AND include any extra work required in your quote for the job.

• This reply was modified 1 year, 11 months ago by Susan Brown.
• This reply was modified 1 year, 11 months ago by Susan Brown.

[Samurai Appliance Repair Man]

on the first video discussing thermal fuses and hi limit tstats

There are seven videos in that lesson. Counting from the top, which one are you referring to?

Update – sorry, I had looked at the wrong unit. I see which video you’re talking about. We’ll get back to you shortly.

• This reply was modified 1 year, 11 months ago by Susan Brown.

[Samurai Appliance Repair Man]

Chassis refers to the metal framing of the appliance. The chassis is grounded either at the terminal block or at the circuit breaker, depending on whether it’s a three-wire or four-wire configuration.

The power supply is Line and Neutral, not Line and Ground. However, in a three-wire configuration, any bare metal place on the chassis– frame, screw head, etc– will work as a Neutral reference point for your voltage measurements. This is because Neutral and Ground are bonded right at the terminal block in the back of the dryer. So chassis IS Neutral in a three-wire configuration.

This is not the case with a four-wire configuration because Ground has its own connection all the way back to the circuit breaker box. So at the appliance, Neutral and Ground are not bonded. This means Ground is not a reliable substitute for Neutral in a four-wire configuration. How do you know the Ground wire isn’t broken on its way back to the circuit breaker box? Is the Ground actually attached in the circuit breaker box? I’ve seen lots of stupid sh*t when it comes to wiring (and plumbing) and I’ve seen techs get head faked by using Ground as their reference, thinking it’s always equivalent to Neutral. Not always true!

This webinar recording at Appliantology goes into some more detail about this distinction. You can watch it over at Appliantology here: https://appliantology.org/topic/82369-dryer-cord-wiring-weirdness/

[Samurai Appliance Repair Man]

Troubleshooting control boards is not something you will be doing at first. The first thing to master is troubleshooting circuits in an appliance using the schematic in the tech sheet. Sometimes your troubleshooting reveals a failed main board and you replace the board.

The big problem with troubleshooting boards is that the manufacturers do not make the detailed circuit schematics for the board available to us. How do you troubleshoot circuits without a schematic? It pretty much comes down to inspecting and guessing. Sometimes, the problem is visible, like a burned trace or a burned triac. Other times it’s not because a component has failed internally with no visible signs.

The other problem is that to test any of the individual components on the board, you would need to unsolder at least one lead on the component, like a diode or a capacitor, in order to test it. This quickly becomes a time consuming job that is much less profitable than simply replacing the board. Whatever markup you make reselling a board that you repaired would be more than eaten up in the time you put into doing that repair.

[Samurai Appliance Repair Man]

As you learned in the Core course, if you apply voltage to a circuit with a single load, when electrons start moving in the circuit, all of the source voltage will be dropped across the load. So you won’t be calculating voltage drop in this scenario.

If there is an open in the circuit so that no electrons are moving, then you will not have any voltage dropped across the load.

Remember: Voltage is the first cause of everything else happening in the circuit. Voltage Drop is the effect of electrons being moved by the source voltage in circuit as they are forced through the resistance of the load.

[Samurai Appliance Repair Man]

They’re not available anymore. They stopped making them. But there are better ones out there now. Go to Amazon and search “portable oscilloscope”. Lots of choices.

[Samurai Appliance Repair Man]

I use several, depending on the situation:

1. First (and easiest and cheapest) method is using the teflon slides that go under the footings. You can get this at hardware stores or Amazon. They’re just wide channels of teflon (plastic) that snap together to accommodate different lengths.

2. Air sled. Expensive and not often used but when it is, it saves the day (and the floor). Since it is a capital cost, I charge a $75 surcharge whenever I have to use it. If the customer complains, I tell them they can save the 75 bucks by moving the appliance out themselves. I’m an appliance tech, not a mover or installer. For moving refrigerators, you want to make sure the slides are under the edges of the cabinet, but in the middle of the fridge where it could damage the condenser. Same with some ranges.

3. All dolly. Also expensive and not used much but it mandatory on some wall oven jobs. Again, $75 surcharge when I need to use it.

4. That little rolling stand you saw in one of my videos. Bought it decades ago through Marcone. Don’t remember what I paid but it wasn’t much. It’s light and portable, stays in my vehicle. Very useful for some washing machine jobs. Used to use it to replace the belt on the old Whirlpool belt drive washers. Since I’ve had it so long, I don’t surcharge jobs where I need to use it.

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