microwave repair - Page 1
Forum section: electronics / repair

author: kpn
author_rank: Newbie
timestamp: June 23, 2025, 12:11:22 am
content: hi, i'm trying to repair my microwave, i'm a novice electronics repair lover/hobbyist. the problem occurred yesterday when i was trying to degrease the microwave and accidentally sprayed degreaser into the compartment with all of these bits inside lol. the first couple times others used the microwave there was a muffled pop. i turned it on after allowing it to dry out for several hours and it worked. then we used it again about an hour later and there was a VERY loud pop and the diode lit up like a lighting bolt and it smelled of burning plastic. i disassembled metal shield, cleaned up, tested again and diode lit up bright and another very loud pop. HV diode and new fuses arrive tomorrow, but, i discharged the cap and am now wondering why i did that and if it will recharge and work well again. please help, thanks in advance!

author: Psi
author_rank: Super Contributor
timestamp: June 23, 2025, 12:40:34 am
content: novice + microwave is a bad idea. Many people have died messing with microwaves.You almost never get a second chance if you accidently touch 2kV, you just die instantly.It's orders of magnitude more dangerous than having 240VAC flowing through you.But warnings aside. The cap will charge up again just fine. Assuming the cap is ok. Sometimes the caps fail internally and you get a bang as they arc inside.Sometimes arcing causes black carbon deposits on things and that carbon path provides an opportunity for a new arc to form when you turn it on.So, after everything is discharged and safe, any black carbon around any high voltage parts must be totally cleaned off.And keep in mind that discharged high voltage caps can recharge themselves from just sitting around. Just because you discharged a HV cap yesterday doesnt mean it's still discharged today. Correct procedure is to permanently short the terminals with some wire so they cannot self-recharge while sitting around.

author: CaptDon
author_rank: Super Contributor
timestamp: June 23, 2025, 02:07:24 am
content: Nearly all newer microwave capacitors include a 10 megaohm internal bleeder resistor and many show the resistor schematically on the side of the capacitor or verbally state it is included. You have already shown you are pretty damn careless around a high power high voltage electronic device. Hope it works out for you.

author: kpn
author_rank: Newbie
timestamp: June 23, 2025, 03:03:42 am
content: thank you, i didn't know some of these things. the second round of pops were really loud, enough to scare. i'm in over my head, but since the diode and fuses are in transit, will replace those and if it doesn't work will buy a new one. not going to mess around with the capacitor, as the platter mechanism is broken (no spin), microwave is 12 yrs old and it's super greasy everywhere inside (and i don't want to be dead).

author: joeqsmith
author_rank: Super Contributor
timestamp: June 23, 2025, 03:55:22 am
content: Whats a new microwave cost in the USA? $100? $500? Trying to see what price you put on your life.I posted a report recently about some wannabe working on microwaves with their Fluke 101. They provided a few photos of the guys workbench. Died.My most memorable to date was the kid in Ohio that cooked himself. Parents smelled him from inside the house.

author: analogueAdder
author_rank: Contributor
timestamp: June 23, 2025, 04:09:26 am
content: Just searched Amazon and found models from $60 to $500.You should be able to get a decent microwave for $150 or so. Everything will work on it, it won't be a greasy biohazard, and you'll live to see another day and another hot pocket...

author: Psi
author_rank: Super Contributor
timestamp: June 23, 2025, 01:43:51 pm
content: Quote from: kpn on June 23, 2025, 03:03:42 amYep, microwave capacitor stores a very lethal amount of energy. If an arc occurs across the HV cap for some reason the discharge of all that energy in an instant is very loud and very sudden. Can be almost like a gun going off with some of the higher-power microwaves that use larger caps and higher voltages.With even larger industrial HV capacitors, where the capacitor is the size of a suitcase, shorting them out can blow-out the windows in the room. And, if that insane current flows through a human the moisture inside you turns to steam so fast you literally explode. Like a tree getting hit by lightning.

author: kpn
author_rank: Newbie
timestamp: June 23, 2025, 02:10:53 pm
content: okay, returning the fuses and diodes, buying a new microwave. thanks gents...

author: Gyro
author_rank: Super Contributor
timestamp: June 23, 2025, 06:10:19 pm
content: Quote from: kpn on June 23, 2025, 03:03:42 amJust another risk, that may help others, as you have now chosen the wiser path. Most microwave ovens have done away with the rotating (air blown), 'wave splasher', at the top of the cavity, that used to be used to move the heating nodes and nulls around the cavity. Without the platter rotating, you are likely to get heated and cold nodes within the food, adding the risk of food poisoning!I believe some expensive microwaves - the ones with a rectangular cooking area to increase capacity, use some clever technique to even out the heating of the food but these are not common.Cue a turntable motor replacement too, although these tend to be a simpler replacement via an access plate in the bottom of the case, with only mains voltage risk to contend with.

author: Psi
author_rank: Super Contributor
timestamp: June 23, 2025, 10:48:37 pm
content: A tip for putting things in a microwave.Don't do the aesthetically pleasing thing of placing smaller items perfectly centered on the rotating platform.Instead, put the item as far to one side as you can get it. You want the food moving in and out of the hot and cold spots as fast as possible to even out the heating. The center rotates the slowest so is the worst place to be!Obviously for larger items you can't avoid the center, but for small items avoid the center as much as possible.

author: analogueAdder
author_rank: Contributor
timestamp: June 24, 2025, 12:28:54 am
content: Quote from: Gyro on June 23, 2025, 06:10:19 pmI've never seen a microwave oven with one of those. Most microwaves now have the "broiler" on the top of the cavity which never gets used, becomes gross over time, and it's impossible to clean...Well, at least I get to feel young for once.

author: CaptDon
author_rank: Super Contributor
timestamp: June 24, 2025, 12:38:13 am
content: I don't know if I would have gone as far as returning the parts already paid for and shipped. For shit sakes, we repaired hundreds of microwave ovens at my fathers radio/tv/appliance repair shop and not once did we encounter shock or death just using simple common sense!!!! Unplug the mains cable and bridge the capacitor with an insulated jumper to make sure it has no charge!!! 99% of the caps you will ever see in recent times have the bleeder built in. Can/will the capacitor regain charge?Not if it is bleeder equipped AND I have never seen one gain more the 50 volts after being discharged and that one was early production Amana with no bleeder. Don't exceed your skill set, but don't let all of these Chicken Little's scare the shit out of you trying to repair a unit with safety features built in!!!

author: Psi
author_rank: Super Contributor
timestamp: June 24, 2025, 07:34:26 am
content: Quote from: CaptDon on June 24, 2025, 12:38:13 amYou worked at a repair shop. He called himself a 'novice' electronics repair lover/hobbyist.It was perfectly correct of us to point out the dangers.No one in the thread told him to not repair it, and we even gave him info to help the repair.It was simply important he understood the extreme risk of making 1 silly mistake with a microwave MOT/Cap.We were all an electronics novice at some time, and have all made stupid mistakes and got zapped from 110V/240V on multiple occasions. I don't think it's unreasonable to point out the much higher danger of making those novice mistakes with a 1-2kV source or charged cap.If he doesnt feel comfortable working on it at his current skill level after reading the dangers and decided to return the parts, good on him. It's a good life skill to know when to "not" do something.

author: Gyro
author_rank: Super Contributor
timestamp: June 24, 2025, 12:13:06 pm
content: Quote from: analogueAdder on June 24, 2025, 12:28:54 amYes, Iamtalking mid '80s here. The 'splasher was made of thin alloy, with widely spaced vertical fins, a bit like a very lightweight and inefficient centrifugal fan rotor. It was simply hung from a post in the lid of the cavity, retained by a circlip. There was a removeable thin woven fibreglass/mica sheet placed below the 'splasher' to keep it clean and give a more esthetic look to the cavity. It was spun by a small amount of air from the Magnetron cooling flow.I have a feeling that more recent the non-turntable Microwaves have something similar, positioned below the cooking area - I have yet to see one with a nice stainless steel interior, they all seem to be some form of plastic, which would make sense. Mind you, it's a while since we looked.