After writing my last post about salvaging parts from CRT TVs, I wanted to write about salvaging stuff from microwave ovens. It's a bit more dangerous to teardown microwave ovens but you can obtain a ton of unique parts. If you do go through with taking apart a microwave, you'll find parts to help you with every project from basic electronics to XRay emission to high voltage to high current.
But first, an important safety warning. Do not attempt to open a microwave oven without knowing what you are doing. There are parts in here that can kill you, even if the microwave oven has been off and unplugged for a long time. If you decide to take apart a microwave oven, follow safety steps in multiple guides to the T to avoid a dangerous high voltage incident.
Microwave Oven Overview
First let's briefly go over how microwave ovens work. 120VAC output from a wall outlet is stepped up to around 2,000 volts via a large transformer. This is then doubled to around 4,000 volts using a single stage cockcroft-walton multiplier, which uses a single high voltage diode and capacitor. This high voltage is then used to power the oven's magnetron, a specialized vacuum tube used to produce 2.4 GHz microwave radiation. This radiation is incident on the internal chamber and heats up your food. Note that microwave radiation isn't "radiation" in the commonly used sense - it can't cause cancer because individual microwave photons are far too low energy to ionize atoms. It is only able to heat up food and water because several hundred watts worth of RF energy is being put into the chamber.
Internals of the magnetron vacuum tube. This device is responsible for producing the actual microwave radiation that cooks your food.
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In addition to the main magnetron system, a lot of supporting electronics are present, including a stepper motor to turn the food, a fan, and a timing panel for actually setting the oven's run time.
Getting the risky part out of the way
You will need the following to safely defuse the microwave oven capacitor:
- Conductive screwdriver with insulated handle
- Insulated gloves
- (Optional) Insulated handle pliers and a high wattage resistor
Once again, consult multiple sources before attempting this.
I can't really understate the danger here. One of the components of the voltage doubler at the HV output of the transformer is a huge 2,000 volt capacitor. These capacitors usually contain a high value resistor to drain the charge when the oven is off for safety reasons, but if for some reason this resistor fails then the capacitor will stay fully charged when you open the microwave oven. If this capacitor passes current across your body, it can kill you.
And above all, never open a microwave oven if it has been plugged in during the last 24 hours. Opening these ovens while they are plugged in is an incredibly easy way to get yourself killed. Don't be an idiot and consult multiple guides to ensure that you safely disarm the internal capacitor before proceeding.
To do this, you will want to take off the back plate of the oven while wearing insulated gloves. Don't stick your hands inside the oven, just remove the backplate to the best of your ability. Be extremely careful not to touch anything inside the oven. Your goal is to locate the HV capacitor. It will look like a large metal can, something like this:
Now you have two options to discharging the capacitor. The first is to touch the conducting screwdriver to both capacitor terminals, while only touching the insulated part of the screwdriver and while wearing insulating gloves. This will likely produce no sparks and you are free to disassemble the microwave oven. However, if for some reason the capacitor is charged and you attempt to discharge it this way, it will produce a huge flash and a loud bang, and may damage your screwdriver. Be prepared for this if you go with this method.
The other way to discharge the capacitor is to grab a high wattage resistors with pliers. While only touching the insulated handle of the pliers and wearing gloves, touch the two leads of the resistor to the two leads of the capacitor. This will drain the charge through the resistor, resulting in a discharged capacitor without the large flash/current produced by shorting it with a screwdriver.
Either way, discharge this capacitor before proceeding or your life is at risk. Consult multiple guides before attempting this for safety reasons. Do not trust me - consult multiple guides!
Salvage!
Now that the capacitor is dealt with, you are free to harvest your reward. I would still wear gloves just in case.
Microwave ovens contain a ton of unique parts, some of which can be worth a decent amount. Expect to find the following in each oven. The location of the parts will vary but each component is typically really easy to remove.
- A 2000 volt capacitor. This can be used to make cockcroft-walton voltage multipliers of your own or build car starter coil high voltage supplies.
- A heavy 120VAC to 2000VAC transformer. While this can be used to make a 2000 volt power supply, I DO NOT RECOMMEND THIS. The reason is because 2000 volts isn't high enough to produce any interesting HV effects (no detectable XRays, arcs will be very short) but the current output of this transformer when powered off of the wall means that you will die if you touch the output due to the very high current. So making these into a HV supply is a massive safety risk for little gain - don't do it. You can, however, look up a guide to rewind the HV secondary coil to change the transformer into a device that converts 120VAC into low voltage (5V or so) very high current output that can melt chunks of metal. This is safer but still not safe due to the 120VAC, so do your research first.
- A timing circuit - essentially the entire timer panel for the microwave oven. If you don't want the timing circuit, you can pull off some parts like the piezoelectric buzzer.
- A 120VAC turntable motor. This is used to turn the plate of food. You can use these as a motor of course, but they also can be used to make a hand-cranked low power 120-200V generator. I've used this to light neon lights but haven't actually assembled a generator yet - apparently you can get really low power phone charging off a usb wall charger with this but I'm skeptical.
- Several decent switches, used to turn off the oven when the door is opened.
- Several temperature switches which turn on/off when a temperature threshold is reached.
- A big 12 volt fan, that can be used for all of your cooling needs.
- A high voltage diode, attached to the HV capacitor.
- A vacuum-insulated incadescent bulb. On top of being useful as a light, you can use some aluminum foil to turn these into somewhat useful XRay vacuum tubes. Put an aluminum foil cap on the top of the bulb, run 15,000 volts or more between the foil and filament, and observe XRay emissions on any geiger counter. A gentle reminder not to do this without utilizing HV and radiation safety techniques. Look this up online for more info.
- Two useful big ceramic ring magnets from the magnetron. But see below first:
A word on disassembling the magnetron: Many magnetrons contain an insulator called beryllium oxide (BeO). Beryllium is extremely toxic in pure form and in BeO and can cause a permanent lung disease called berylliosis if inhaled. This makes the magnetron the second most dangerous part of the oven after the capacitor. Take this seriously. This means that if you want to go after the magnetron for the two big magnets, be incredibly careful not to damage, scrape, or fracture the pink insulator caps on the magnetron. If you don't know what you're doing, just skip the magnetron and dispose of it in a safe way (e-waste event).
A microwave oven magnetron. This dark purple cap on the right is the insulator. This can be either aluminum oxide or beryllium oxide - better not to take the risk.
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I've taken apart two microwave ovens so far, given to me for free. You can find these on the side of the road for free as well, although less commonly than CRT TVs. That being said I think the overall gain is better than for CRTs, although CRTs will give more basic electrical components.
If you need any of the above for a project, then hopefully you find this writeup useful. Remember to be safe. I'm not responsible for your safety if you attempt this without consulting multiple sources. Please look after yourself, taking apart these ovens is very dangerous if you go in blind.
Here's part of my haul from the first microwave oven I took apart about a year ago:
Thanks for reading! STAY SAFE!
Images not credited are my own. You are welcome to reuse them with credit.
You sir are a badass and I thank you for your microwave oven hackathon
thanx for this!