Repairing A Broken Microwave Keypad


[Alexandre Souza] needed a microwave pretty badly, but he didn’t have a lot of cash on hand. He located one for a great price, but once he got home he found that things weren’t working quite like they should be (Google translation).

After some investigation, he narrowed the problem down to a bad keypad membrane. Unfortunately for him, this model of microwave was never sold in Brazil (who knows how it got there) and the only membrane he could track down had to be shipped in from the US at a cost of $80.

Rather than pay such a high price for a simple membrane, he opted to fix the microwave himself. He dismantled the control panel and thoroughly traced the keypad matrix to get an understanding of which pins toggled which functions. With a piece of protoboard and almost two dozen push buttons in hand, he built his own keypad and wired it directly into the microwave’s control board.

With labels written in marker it might not be the nicest looking thing you have ever seen, but it works a treat and is a great money-saving hack.

41 thoughts on “Repairing A Broken Microwave Keypad

  1. It’s pretty sad that you could have 1) a brand new microwave shipped in or 2) a replacement keypad that you still have to install.

    For the exact same price.

  2. great work! I once fixed a car stereo by hard wiring two control boards back onto the main one. My friend that gave it to me because it was broken was so pissed that I was able to fix it and wanted it back ;)

    I get the most satisfaction by fixing things that weren’t “meant” to be fixed by the end-user.

  3. It’s not the most attractive-looking keypad, but there’s something strangely appealing about the way this thing looks to me. Maybe it’s because this is how I imagine salvaged and repaired equipment would look in a dystopian future where electronic parts and devices are no longer manufactured.

    I think I would have used a calculator or phone keypad instead, at least for the numbers.

  4. This will probably last longer than the membrane keypad, be more reliable, and be far more easily fixed in the long run. Now if he could just get it inside the microwave and make like it did when he got it that would be really good.

  5. After disucssing this with a collegue we both agree that this is rather dangerous as most microwaves do little to segregate the high voltage circuitry with the low voltage control. This will likely result in shock to the end user. Not an ideal solution.

  6. Mike: Sounds like a challenge… Maybe you should make a keypad for one of those microwaves and write about it! I assume the dial is just a timer and a switch, so it could be replaced pretty easily with a relay and an MCU.

  7. Thanks for the comments, here you have more info:
    – A microwave like this in Brazil costs upwards R$ 400 (some Us$ 230). So buying a microwave for $50 is a no-no here.
    – I’d love to make it prettier. But I was hungry and need to heat a lasagna. You know how fat people get when hungry :8)
    – I could use a nicer keypad but this was everything I had at hand, and as I said, I WANTED LASAGNA!!!:8D
    – Maybe in the future I’ll build something nicer and retrofit it. I know it is ugly, but as someone said, it works and the buttons will outlast the oven. For me, it is perfect, I like the “mad max repairs” look of the microwave.
    – It got in Brazil by an american resident who came live in Brazil and brought it abroad.
    – Greetings from Brazil! ;oD

  8. Tbh I wish my microwave had buttons rather than a dial.

    If I had the time or motivation I suppose I could replace it all with a digital counter.

    Mad Max repairs are awesome, btw. :3

  9. Not only a fluke meter…A TDS420A tektronix digital scope, a HP16500C logic analyser mainframe fully stuffed, HP8656B signal generator, HP5328A frequency counter, Tek (something)video generator, fluke (something) video line selector, hitachi V1100 analog hybrid scope, HP75000 VxI measurement mainframe, a pair of tek TM504 mainframes fully stuffed, weller soldering irons, lindstrom pliers…I could speak for days :) I only buy quality tools. I wait day after day to spot them cheap, but I only use quality tools.

    A photo of my (messed up) workbench can be found (missing some instruments that wasn’t there yet) here:

    That was bought along 25+ years working with electronics. I needed this microwave NOW and hadn’t money NOW to buy a new one. So I did it, for your amusement :D

  10. Well done – I did exactly the same thing in the mid-90s with a cheapy microwave that had a failed membrane keyboard. A poster has alluded to a potential HV risk – that’s easy to test for and on the board I had the lines went directly to an ugly great chip – and if *that* had been floating at mains potential, it’s a heck of a risk to separate a user only by puncturable plastic.

    Safe hack – well done.

  11. The whole POINT is that something was kept in useful service by sheer will to make it work and the skill to do so in an effective fashion.

    In a better, seemingly vanished time we’d have had that membrane be priced closer to $10 USD delivered.

    Perhaps some of the price delta for our Fellow Hacker in Brazil is Duty/Tariff driven? There’s a few countries where political embargos etc have spawned a body of REAL intense Hackerdom that’s sadly under our radar.

    As for the “Knobs Vs Buttons” in microwave oven controls. I live 50 miles N of Kansas City, MO which is a VERY high lightning area. Those electromechanical timer knobs are almost immune to surge damage short of a direct nearby line hit. And the Air Gap contacts also increase protection for that HV diode in the Magnetron PSU circuit. Yeah, it’s a bit more human skull sweat to suss out the knob setting Vs punching 55 secs for my sausage biscuit. But not having to hack up a keyboard has points too.

    The closer- many keyboard failures were and ARE caused by ultrasurfactant+ammonia cleaning stuff seeping intot he laminated keypad- and corrosion of contacts destroys the assembly.

  12. Oren, the membrane for this oven – I was able to find it only in USA is $80 **just for the membrane**, without shipping/taxes/whatever. Incredible, you can find most membranes in Brazil for $6-7, but this oven is unobtainium. That is why I did this hack. Ok, I could afford a newer/new oven, but it IS A WASTE to throw this oven away just because the lack of a keyboard. The hack took me 3 hours away from my sunday, and I had lots of fun. Why not? :o)

    Haaram, Pardon c’est français…”sorry” in portuguese is “perdao” ;o) Mas voce fala um portugues até legal heim? :D

    Thanks for all the comments, and I hope this hack make us think that it is fun to repair appliances and maybe don’t need a new one ;o)

  13. Brazil has import taxes on electronics to protect the local industry.

    @Mike, where are you? I prefer dials, I (like most people) don’t use anything beyond the time setting (occasionally power). The problem is that people buy the product with the most features…

    FWIW, almost all ‘dead’ microwave ovens aren’t. Usually they just have a blown fuse.

    Membrane keyboards fail when water gets in, so being a slob and not cleaning it promotes microwave oven life.

  14. Would you have made hack-a-day if you’d have just bought a new one? Why don’t the trolls understand that the fun is in doing the hack, not necessarily the end result! Geez

  15. Tech, although I enjoyed your commentary, I still thinks that IN MY CASE is better to have a repaired (as klunky as it was done) microwave oven than buy a new one. This microwave is **new** but the keyboard. I see no why to spend hundreds of reais (our local currency) when I can spend next to nothing and have the same funcionality. Most of my (extensive list of) test gear was bought very old, as surplus, broken or the sum of all that :) I spend very little money compared with the current list price of the toys. WHY NOT? My girlfriend hates it, she likes to buy everything new. Nice for her, I like to repair and, when I use, I say “I repaired this, and it was cheap, I feel well” :oD Helps a lot on reciclying too :oD

    And the most important: IT WAS FUN! :oD

  16. Look at all the America-centrics here. For those who can’t seem to understand it, Brazil is NOT America. They do things quite a bit differently there. Pricing is a lot higher on certain things than it is here. It’s not as simple as “throw it away and get a new one.”

    I love this hack! It’s something I wanted to do to an old microwave until I found out the magnetron was broken.

  17. I also love this hack.

    Learning about the keyboard matrix; keeping something out of landfill; not just buying a new machine or even a new part.


    And, now it’s been done, “nicer’ panel can be made someday really easily.

  18. Hey, let’s leave Alexandre alone….it’s a great hack. Reminds me of a fix I did to a salvaged microwave in the 90s.

    I didn’t bother with the keypad route though. I rigged up a switch (NO TIMER). My microwave was on/off. The door interlock worked, so it was relatively safe.

    A friend suggested attaching it to the clapper and turning on wheel of fortune for power level settings between 10 and 100 percent.

    Nice way to save what would be scrap metal.

  19. Thank you for sharing! My microwave just stopped working one day, I don’t know what happened. It was kinda making some weird noises the past few days and then it just stopped completely. I am not sure if I am going to attempt fixing my microwave because it seems dangerous. I just need to find a professional that can help me fix it. It isn’t very old so I’m assuming that it would be worth it to fix. Thanks again.
    -Chris |

  20. All good things must pass…
    After almost 10 years, I gave up. I moved home and got as a gift…ANOTHER BROKEN MICROWAVE =D But this one was newer and way more beautiful. Time to pass the old trusty to another poor one who needed that.
    May the tradition live, and this microwave be a symbol of recycling broken goods forever! \o/

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