Bleeding Diode Shorted
This week was a crazy repair week for me since most of the repair devices brought to me were microwave ovens that do not produce heat.
This one had the issue of no heat and there are many reasons why such issue takes place in a microwave oven.
Usually, the magnetron head is the main suspect, either it is faulty of components around it are faulty causing the no heat in this device. First and most important thing to do is discharging the main capacitor.
This is the main capacitor and by touching both terminals with two insulated screw drivers you might hear a little or sometimes big zap in that area. Please I cannot stress this enough, discharge it before doing any repair on this device.
Now that it is safe to work on this device, let us begin. If you can see the white plastic piece in this photo, that is the fuse holder and when testing with a multi meter, I could see that the fuse was intact.
That is the magnetron head that is responsible for heating and by setting the multi meter to ohm and testing between, the two pins and the body of the heat; there should be no reading what so ever. In my case the head was damaged and had to be replaced.
This is a brand new magnetron head and I replaced directly in the place of the faulty one.
That is where the magnetron location in the microwave oven. Two screws holding this head and very easy to replace.
Before any testing, usually when I replace the magnetron, I test the bleeding diode that is attached to the capacitor and see if that is shorted to ground or not. Usually, when testing it with a multi meter, the meter cannot measure it and it shows open both ways but sometime it shows that is shorted and that is the indication to replace it.
In my situation, the bleeding diode was shorted to ground. When replacing a diode, pay attention to the lines presented here. If you look closely to the diode in photo, you will see three lines and the replacement has to be the same otherwise we will have some issues. So far, I did not find an explanation on the net about these lines but I got used to the fact to replace faulty diodes with the same exact image.
Here you can see the bleeding diode with clear lines on the left side of it. After replacing these two faulty parts, I powered on the microwave oven and heated some water in a cup and it was totally up to specs.
Mission accomplished.
This article was prepared for you by Waleed Rishmawi, one of our ‘Master Authors’ and currently working in the Bethlehem area of Palestine repairing electrical and electronic equipment.
P.S- Do you know of any your friends who would benefit from this content that you are reading now? If so, forward this website to your friends or you can invite your friends to subscribe to my newsletter for free in this Link.
Note: You can check his previous repair articles in the link below:
https://jestineyong.com/xbox-drive-rejecting-cds-repaired-model-xbox-one-s/
(70)Dislikes
(0)
16 Comments
Leave a Reply
Parasuraman S
March 23, 2020 at 11:58 am
Good job there! Straight to the problematic component! Well done!
Waleed Rishmawi
March 23, 2020 at 4:47 pm
Parasuraman: thank you man. hope all is good with you. have a blessed safe day
Eric Rice
March 25, 2020 at 11:52 pm
There is a Chinese Fluke multimeter (Fluke 17B) with the diode tester (made in and for the China market) that is fairly inexpensive as far as Fluke meters go. I recently purchased one for $125.00 US. If purchased direct from China it is nearly $40.00 cheaper! This is a lot, but having a true diode tester is well worth the price. Most diodes (probably around 98%) can be tested in circuit, which a regular multimeter cannot do this.
Albert van Bemmelen
March 23, 2020 at 1:32 pm
Okay Waleed, you meant the 3 marking lines on the diode because at first I was confused what 3 lines you were talking about since the diode only had two legs. I suppose it is the cathode marking? Very nicely detailed article!
Waleed Rishmawi
March 23, 2020 at 4:48 pm
Albert: that is why I added a photo of it so you will know what I am talking about. have a safe blessed day my friend
AR Balasubramaniam
March 23, 2020 at 2:23 pm
Few weeks back, I have replaced Magnetron ( which was earlier brand new replaced under warranty period)
Oven is working
Still I doaut Magnetron failure
Is there any methodology to confirm.
Otherwise reason for the failure
Please let me know
Waleed Rishmawi
March 23, 2020 at 5:23 pm
AR: not sure what you are asking here? usually for testing a magnetron, with your meter set on ohmes test between the pins and the body of the magnetron and you is should be open reading there otherwise it is bad. sometimes no power to the primary pins of transformer would a a no heat issue in the microwave oven. I hope this answers your question. if you have any further question do not hesitate to ask. have a blessed day
Gassan Ali
March 24, 2020 at 5:41 pm
Great repair! The more I read from experts like you, the more it makes sense. Like how you explained testing the magnetron. I think you're testing for shorts between the pins and its body. Thank you!
Waleed Rishmawi
March 26, 2020 at 7:58 pm
Gassan: thank you. have a blessed day
Louis
March 23, 2020 at 2:55 pm
The diode is NOT a bleeding diode.It together with the capacitor is a voltage doubling circuit which helps with the high voltage to excite the magnetron
Waleed Rishmawi
March 23, 2020 at 5:18 pm
Louis: I appreciate your input but if you enter the part number of the diode, it will tell you that? it is a bleeder. it has man names and a bleeder is one of these names. have a blessed safe day
mr tom cassidy
March 28, 2020 at 2:06 pm
well boys and girls call it what you,s like as a service enner for over 40 years i cant emphise enough to make sure you discharge the cap before doing any tests on the micro i was about 24 at the time i heard of two service personal being killed in england for being a bit fool hardy or complasent so please take great care ime now 64 and retired some times defeated but second to none god bless, tom cassidy
Henrique J. G. Ulbrich
March 24, 2020 at 7:11 am
Louis is right. This is NOT a bleeding diode. It is a conventional (although for HT) diode used in a voltage doubler circuit. I´ve explained this in my article https://jestineyong.com/a-bad-hv-capacitor-in-a-microwave-oven/.
mr tom cassidy
March 28, 2020 at 2:48 pm
a word of caution when working on any microwave see above notes.
iosef
September 22, 2020 at 11:46 am
gracias Waleed, saludos
Akash Gunjal
October 17, 2020 at 6:33 pm
The silver ring indicates cathode (negative-end) and the black side indicates anode (positive-end)