Toaster PCB Repair

[nmercier]

I have an expensive toaster that will not stay down and after testing found the voltage to the electromagnet does not change. This has led me to believe the pcb component(s) are faulty.



I have done a fair bit of electronics work but this is my first-time attempting PCB repair. My first and foremost question is if I replaced all the components would it be guaranteed to work or is there more to it than that? Second most, I am not sure which are the power pins to the electromagnet, so I just recorded all measurements and found that both DC and AC voltages are read from my multimeter. How/why?

Here is the data I have collected thus far. The following are the voltages for the electromagnet initially and after 5 minutes on the lowest toast setting. I would anticipate the electromagnet to be 12vdc so I am unsure if I am recording what should be the off voltage or on voltage.

Pins 1 and 2: 31.4v AC/0.271v DC -> 31.4v AC/0.276v DC

Pins 2 and 3: 1.92v AC/8.71v DC -> 1.90v AC/8.78v DC

Pins 1 and 3: 29.9v AC/8.80v DC -> 29.9v AC/8.97v DC

The zener diode in the top left of the first image (ZD1) has a 0.512v forward bias and 0.729v reverse bias with my multimeter. Furthermore, the resistor R5 (top right of first image) is reading 0.5 ohms which should be in the megaohms if I read it correctly. This is a 4 slot toaster which has one of these circuits for each two slots. The issue occurs for both with the same faults found. I have not tested the capacitors as I do not have a capacitance test on my multimeter. Likewise, I do not know how to test or read the thermistor; it has 404 written on it and is reading 0.384 megaohms at room temperature.

 

[bertus]

Hello,

Did you measure R5 in circuit?
It can be that other components cause the low reading.

Bertus

 

[nmercier]

Hello,

Did you measure R5 in circuit?
It can be that other components cause the low reading.

Bertus

yes I did. You are correct. Once removed it reads the correct value. Should the zener diode be removed as well for testing?

 

[Bluejets]

2 and 3 appear to be a "slide switch" on the transformer secondary.
Somewhere it needs to start the "toast" process and this is usually done via the "slide" in some fashion.
If this is so, again it appears to be a low quality switch and mechanical (which usually fails before all else) to boot which would be my first check point.

Appears you know sweet f/a/ about how it even begins to operate so advice would be get a new one.

 

[nmercier]

2 and 3 appear to be a "slide switch" on the transformer secondary.
Somewhere it needs to start the "toast" process and this is usually done via the "slide" in some fashion.
If this is so, again it appears to be a low quality switch and mechanical (which usually fails before all else) to boot which would be my first check point.

Appears you know sweet f/a/ about how it even begins to operate so advice would be get a new one.

Transformer? Are you referring to the electromagnet? Does an electromagnet of this type still behave as a transformer? Yes, I probably should get a new one but still want to give repair a reasonable shot.

 

[Bluejets]

Transformer? Are you referring to the electromagnet?

Appears to be both.
Seems when the cage comes down it completes the electrical circuit via the white switch (for the secondary side) and the frame completes the "magnetic core" and hence the holding field.
That is all I can make out from the photos supplied.
There should be some form of primary switching but nothing I can see with the supplied photos.

 

[roughshawd]

Theres a three prong plug on the transformer board, try flipping that over in the other direction first....

 

[73's de Edd]

Theres a three prong plug on the transformer board, try flipping that over in the other direction first.

DON'T DO DAT !
Or even think about that . . . . . . . Which I believe will . . . . even be impossible . . . . due to the white lock in tab at the bottom, only letting that female plug key in one way.
(Ya' sort of pulled off at an angle and skewed end pins ! )
Nmercier . . .

Poster . . . . . stand by, as I am working on creating an analysis report of how that unit works and its likely problem.

But do fill me in on . . . of the fact that it is being a dual toaster with two and two toast baskets.
Then, am I correct that the unit uses two separate push down levers to let the 2 sets of toast baskets down .
You find that NEITHER of the units basket levers will stay down ?
Plus it is replicating the use of those circuit boards for each 2X toast section ?
Try this ...
Put toast in one set and press the corresponding lever all the way down and constantly HOLD IT DOWN.
Then look down inside see if you see the heating elements , then visibly glowing, and warming up, or you can smell a start of the bread toasting.

2 and 3 appear to be a "slide switch" on the transformer secondary.

I don't see those terminals as being or connecting into that , but merely as connections into the transformer.
More of the info on that transformer and its 3 connections in my upcoming . . . . . . THE REST OF THE STORY . . . . .

73's de Edd . . . . .