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Dave Saylor
Joined: 11 Jan 2015
Posts: 209
Location: GILROY, CA
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 Posted: Wed Dec 20, 2023 5:27 pm Post subject: Non-aircraft question (OK, maybe a plane with a galley) |
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I'm trying to troubleshoot my microwave oven. I was able to identify and replace a failed capacitor. But it still has the same problem in that it makes a loud buzz for half a second, then blows the house breaker or the internal 20A fuse.
I tested the magnetron for an open circuit, it tests OK according to a few sources on the internet: about one ohm across the terminals.
These diodes are attached to the capacitor terminals. When testing, I can't get my DMM to say anything but OL. I tried diode/beep continuity mode and regular resistance mode but both just say OL, same for the new parts and the old parts.
I don't recognize the nose-to-nose diode symbol. I assumed the big arrow points to what would be the banded end on the replacement.
The replacement says "2X062H" on the package and in the sales description, but "6X3PI" printed on the body. The replacement is cylindrical while the original is a long box.
If someone can help me out I'll make popcorn for ya! Any ideas before I scrap this thing?
--Dave
Old diodes:
[img]cid:ii_lqei14hh0[/img]
Same old diodes:
[img]cid:ii_lqei24031[/img]
New diodes:
[img]cid:ii_lqeilit32[/img]
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Eric Page
Joined: 15 Feb 2017
Posts: 247
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| Posted: Wed Dec 20, 2023 7:18 pm Post subject: Re: Non-aircraft question (OK, maybe a plane with a galley) |
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Unidirectional high voltage diodes like the CL01-12 in your oven, when paired with the HV capacitor, form a voltage-doubler that raises the transformer's ~2kV output to ~4kV to drive the magnetron. These diodes have a forward voltage that's too high for a DMM to test, as it can't check any diode with a forward voltage higher than it's own battery supply.
Here's a short video that shows how to check a HV diode: https://www.youtube.com/watch?v=Cx8Q5crqKaw
The "SK" (Sanken) 2X062H is a bidirectional HV diode. Very difficult to test, as its breakdown voltage is something like 5-6kV in one direction and 1.5-1.7kV in the other. Its purpose is to protect the transformer and capacitor by blowing the fuse if the magnetron develops a short circuit (in a healthy oven, it does absolutely nothing). The 6X2P1 is a replacement for the 2X062H. Sanken's website has no listing for the 2X062H; it appears to be obsolete.
You can check if one diode in the bidirectional package has failed short by doing the same test as shown in the video above, in both directions. If you can get a voltage reading in one direction, then the opposite-facing diode has shorted.
Here's a video on testing the transformer windings: https://www.youtube.com/watch?v=rtzPCItrcr8
And finally, here's a video showing how to test the magnetron: https://www.youtube.com/watch?v=_Oriae3-N8c
Resistance between the HV terminals is only half of the story, so be sure to do the second test in the magnetron video. They can also fail by developing a current path from a HV terminal to their metal case. This will bring the bidirectional diode into play, which would explain your oven's symptoms. If you blew the breaker with the new diodes installed then it's likely that they were damaged, so be sure to test them again before you do another powered test.
-Eric
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user9253
Joined: 28 Mar 2008
Posts: 1927
Location: Riley TWP Michigan
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| Posted: Thu Dec 21, 2023 1:17 pm Post subject: Re: Non-aircraft question (OK, maybe a plane with a galley) |
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I had the same problem with my microwave. The problem was the door
switch. Evidently the microwave was designed so that if it operates with the
door not fully latched, then it will short out the power supply. How dare them
design something that blows the house circuit breaker which could cause the
refrigerator to quit and spoil food. I bypassed that switch. The microwave
has been working fine for years since.
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