Susan Brown

[Susan Brown]

The switches determine which route L1 takes.

[Susan Brown]

First, I always like to make sure we are looking at the correct light on the schematic, since there are several.

Any load that is supplied with L1 and L2 will run on 240v. L1 and N is 120v.

There are two ways that L1 can get to the light – that is what we are asking for in Question 2.
One of them is Through the light’s bimetal switch, as you say. The other has to do with that jumper wire (BK-J).

Did you see the explanation that showed up on the results of the quiz for this question?

When the surface element is first switched on, the light gets L1 through the L1 to H1 contacts of the infinite switch and the black jumper wire. This can be easy to miss because the two ends of the black jumper aren’t explicitly shown as being connected.

During the element’s operation, once it gets hot enough, the light’s bimetal switch closes, providing another path for L1. This means that even after the infinite switch is opened, turning the element off, the light stays lit until the element cools off enough for the light’s bimetal to open again.

[Susan Brown]

Check out this topic – does it help you see the answer?

https://my.mastersamuraitech.com/appliance-repair-course-support/student-forums/topic/mod-6-unit-7-quiz/

[Susan Brown]

I assume you are talking about the closed detector switch having an impact on the circuits.

I think the easiest question to answer first is the voltage drop across the Safety.

If you do the “Zen Trick” (see the first video in Unit 5), is the Safety in parallel or in series with the other loads? Does that lead you to know what the voltage drop would be across it?

[Susan Brown]

Hi John,

All 120v circuits will have N at one end of their schematic, and “Line” on the other end – often shown as L1.

Line voltage is 120v with respect to Neutral.

When you see L1 and L2 on either end of the diagram, this indicates a 240v circuit, because both sides of the circuit are providing 120v which combine to form 240v.

We’ll describe this in more detail in Units 6 and 9, so hopefully it will all become clear then!

[Susan Brown]

Hi David,

These are the two parts of the schematic I look at to answer the questions you missed. For example, question 8. You need to know where the bake and broil ignitors are, so you can see which test points correspond to which one. And since they are designated with letters, you need the key to figure out which is which.

Do you see what the test points are for the
1. Bake ignitor
2. Broil ignitor

You would want to look for L1 and N.

[Susan Brown]

Hi Nathan – see the email I just sent you

[Susan Brown]

If an appliance is plugged into (or in the circuit with) a GFCI outlet, and the outlet trips for some reason, that will cut off power to the appliance. Resetting the outlet should restore power.

Non-GFCI outlets don’t have that feature – if they are not providing power it is because the circuit breaker tripped or a wiring issue with the outlet/circuit.

[Susan Brown]

Hi Douglas,

From the unit: “Depending on the model, you can either have a single spark module that sends sparks to all the burners (called multi-point ignition) or you can have a separate spark module for each burner (called single-point ignition).”

I know it seems counterintuitive at first, but if each burner has its own spark module, then it only ignites at that one point. If there is only one spark module for the whole cooktop, that one module needs to ignite at multiple points.

Does that make sense?

[Susan Brown]

Hi Andrea,

The key here is the weird 78v reading. This is the kind of thing you get with “ghost voltage” which is often related to an open neutral.

So the two answers we are looking for are:
That you are probably seeing ghost voltage and should have set your meter on LoZ or used a loading meter to make this measurement
That you are probably dealing with an open Neutral situation

[Susan Brown]

Hi Raja,

#9: we are using “switch” as a verb there. In other words, what does the PCB control: line or neutral?

For #10, see this section of the schematic:

[Susan Brown]

Done!

[Susan Brown]

Hi Denis,

I mentioned this in the Video in Unit 3, around 12 minutes or so in.

It depends on what relationship you are focusing on.

E = I x R is talking about voltage drop (because we’re dealing with a resistance).

Here are some examples that hopefully will help.

Scenario 1
Let’s say we’re dealing with a 120v circuit with two loads in series, R1 with a 40 ohm resistance and R2 with an 80 ohms resistance. So, total of 120 ohms. The current flowing through the whole circuit would be I = 120v/120ohms = 1 amp.

So the voltage drop across R1 would be I x R = 1 x 40 = 40 volts.

Scenario 2
Now let’s say we swap out a different load for R2, which only has 20 ohms of resistance. This will change the current in the circuit.

Our total resistance in the circuit is now 60 ohms, so the current is I = 120v/60 ohms = 2 amps.

The voltage drop for R1 is now 2 amps x 40 ohms = 80 volts. The current going through R1 doubled, as did the voltage drop. So – directly proportional.

Okay, now to talk about power. A typical way we talk about power in appliance circuits is the wattage specification for a load. Let’s say we have a load that needs to generate 500 watts.

If this is a 120v circuit, and this load is the only one in the circuit, then we can figure out what current needs to flow through the load to get 500 watts. P = I x E, so I = P/E = 500/120 = 4.2 amps.

But what if we have a 240v circuit instead? then I = P/E = 500/240 = 2.1 amps. So, when voltage supply went up, current went down.

Does that help?

[Susan Brown]

Hi Quentin,

The short answer is, it depends on the load you’re dealing with and the problem the machine is having. And as you gain experience reading schematics and more familiarity with the various loads in appliances, you’ll get stronger at knowing which tests you want to do when.

Also, which measurement(s) you make will be clearer if you are following the Ten Step Tango. If you have a good hypothesis (Step 5), you’ll know what you need to test. Review Mod. 6, unit 3 of the Core course.

It might also be good to review Mod. 4, unit 7 (Electrical Measurements) as well.

But, in general, the go-to tests are voltage and amps. We have many videos showing us using these to troubleshoot.

Voltage, to see if voltage is getting to a load. If not, you then know you’re looking for an open somewhere between the load and the power supply. If you get voltage at the load, then you’d want to check for current (amps) for your next piece of info. Resistance is the measurement we use the least, as the others are more instructive and reliable.

Let me know if you have any specific follow up questions.

[Susan Brown]

You’re troubleshooting a problem with the oven where neither bake or broil are working. You use your voltage light stick at the ignitors and see that neither is getting voltage. What’s your next move?

Look at the schematic on the left hand side and you’ll see the two ignitors (bake and broil) and the test points that correspond to each ignitor. What you will want to do is energize either the bake or broil, and then test at the appropriate points for that ignitor.

Do you see what the test points are for the
1. Bake ignitor
2. Broil ignitor
?

Let me know what you think they are.

[Author]

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