Microwave oven with burnt connectors on the Magnetron input - Page 1
Forum section: electronics / repair

author: MrOddO
author_rank: Newbie
timestamp: December 11, 2023, 04:33:30 pm
content: Hello guys,My micro wave no longer heats my food despite the fact the board is workingSo I suspect an issue between transformers and the magnetron. Why? Cause I identified a burnt mark in the magnetron input.I've tested:_ Diode: it worked (with 9 volt batterie and multimeter)_ Capacitor tested( multimeter): No continuity well isolated; Measured: 10.2M-OHMS, 1115nF_Transformers : continuity test all are ok I think ?_Magnetron tested the inputs and it looks ok BUT I STILL SUSPECT ITDo you have any idea? Thank you so much

author: CaptDon
author_rank: Super Contributor
timestamp: December 11, 2023, 06:28:06 pm
content: That is a very common problem since the mag filament can draw 10 amps and the connectors develop a tiny bit of resistance followed by burning. Possibly the R.F. bypass capacitors within the magnetron connector are also bad. Typically the magnetron has two 1/4" spade lug style filament connections. If you have a few bucks a new magnetron can be had cheap enough. Then cut the burned connector off of the wires leading to the transformer and install quality spade lugs onto the wires. Plug the spades onto the new mag and you should be good for another 10 years!!

author: MrOddO
author_rank: Newbie
timestamp: December 13, 2023, 08:01:30 pm
content: Thank you for your answer. Let's buy themegatronmagnetron. Will give news as soon as possible.

author: coromonadalix
author_rank: Super Contributor
timestamp: December 13, 2023, 09:36:49 pm
content: optimus wont be far away loll

author: G0HZU
author_rank: Super Contributor
timestamp: December 13, 2023, 11:13:32 pm
content: Hopefully, you know this already, but a typical microwave oven is a very dangerous thing to try and repair.The internal power supply is lethal if you make even the slightest mistake and touch something you shouldn't. You don't get a second chance...My advice would be to dispose of it at the local recycling centre and just buy a new one.

author: coromonadalix
author_rank: Super Contributor
timestamp: December 14, 2023, 12:00:19 am
content: yes you normally have at least a 1200v capacitor who would love to kick you

author: CaptDon
author_rank: Super Contributor
timestamp: December 14, 2023, 12:10:49 am
content: A bunch of Karens telling you you'll get killed. If the thing is unplugged and even assuming the bleeder in the capacitor is bad just get a screwdriver and a bit of wire. Ground the screwdriver to the chassis and touch both sides of the capacitor. I have worked on hundreds of these things at my father's repair shop and basically if it is unplugged and you wait 1 to 2 minutes there is NOTHING lurking to kill you. Use common sense and ignore Chicken Little. If you really want some 'Karen' advice from an old timer who deals with 10's of Kilovolts, well, here it is, Keep one hand in your pocket until you are sure the thing is dead. That way you can't create a current flow across your chest cavity. Another Karen rule, Don't defeat the safety interlocks and stick your head in the oven while it is energized.

author: wilfred
author_rank: Super Contributor
timestamp: December 14, 2023, 01:22:13 am
content: you've used the term "Karen" incorrectly here. Someone who, wisely, is concerned about real dangers present servicing a microwave and not knowing how aware the original poster is of them is not being selfish in raising them.A "Karen" is strictly selfish, entitled, aggressive, rude, insensitive and unwelcome. None of which apply to respondents here.

author: G0HZU
author_rank: Super Contributor
timestamp: December 14, 2023, 12:42:38 pm
content: Thanks. When someone's first post on an electronics forum is about repairing their broken microwave oven I think it's worth warning them about the safety aspects. Even if it ruffles the feathers of the 'experts'.A simple google for "Microwave Oven" and "electrocuted" will show that these devices can be very dangerous to work on. Even when switched off there is a large capacitor inside that can store a lethal charge.

author: CaptDon
author_rank: Super Contributor
timestamp: December 14, 2023, 05:22:54 pm
content: MrOddO, if you feel you can accomplish the simple repair without electrocuting yourself or vaporizing the northern hemisphere then carry forward with the repair. If you had any doubt about the hazards after seeing the warning labels profusely applied everywhere then STOP NOW and as always "Refer servicing to qualified personnel" as stated on the label(s). I am guessing you knew there were certain hazards when you took the cover off. As always, Should you or any of your I.M. Force be caught or killed (or electroplated) the secretary will disavow any knowledge of your actions.

author: coromonadalix
author_rank: Super Contributor
timestamp: December 14, 2023, 06:04:20 pm
content: even an expert as myself can or do forget thingsi tought i discharged correctly an tv crt, i had humid palmsi was greeted with a beautiful 35kv in my body ....while it derail the thread, use caution and be sure the cap is dischargedsome connections / terminals can be changed, if the magnetron is not greasy and shorted out, and the high voltage diode is good, you can try to start itto test an high voltage diode you need at least 6 vdc or more, not a meter diode testput a 32oz glass of water in the oven and put 1 minute to see .... and be sure you are not near the connectionsto probe voltage in theses you need an high voltage probe ....

author: MrOddO
author_rank: Newbie
timestamp: December 17, 2023, 11:07:02 pm
content: You totally right, very dangerous. I had disconnected the microwave oven during 48 hours and I used an insulated pliers to discharge the capacitor.

author: MrOddO
author_rank: Newbie
timestamp: December 17, 2023, 11:27:40 pm
content: Thank you bro,Good news, here to give some feedback. So the the culprit was...the magnetron and I have found that the magnetic ferrite ring has...cracked, please have a look on the pictures.This saturday I have received the new magnetron and put it in the oven. NOW IT'S WORKINGYESS AND I'M STILL ALIVEI think the magnetron was weak due to the frequent usage over the last 7 years.Thank you guys for your advices.If you have any questions...

author: CaptDon
author_rank: Super Contributor
timestamp: December 18, 2023, 03:48:50 pm
content: Strange thing about the older magnetrons as they age and die. Some begin to get gassy, not sure if it is seal leakage or out gassing of internal components but they start cooking even better than new for about 1 month then they die from a cracked magnet because the anode body runs at a much higher temperature. Some ovens have a one-time thermal fuse mounted to the magnetron which will fail when the mag gets gassy and runs too hot. I have seen ovens with a gassy mag melt all of the plastic air dams surrounding it!! Strange how they work better just before they die, kind of like racing engines!!