1
\$\begingroup\$

I have a 40-year old microwave oven. I temporarily attached a magnetic flashlight to the side of it. Its 5/8"-diameter magnet is likely a neodymium magnet, strong enough to secure the 10-ounce flashlight to a metal surface from falling down.

After that, the oven made a humming/buzzing sound when used, and I considered the magnet and removed the flashlight from the side of the oven. The humming disappeared the next time I used the oven, but now I noticed once in a while that the oven doesn't heat at all, or it begins heating several seconds after starting it instead of heating right away (you can tell by the turntable motor's change of sound pitch and the slight dim of the kitchen's lights).

I estimate the magnet was several inches away from the magnetron (I have repaired this oven in the past). So my questions:

  1. Could I have damaged the magnetron with the magnet being that far away? If so, is there any simple way to re-magnetize the circular ceramic(?) magnets of the magnetron?

  2. Why would/how could the occasional heating problem be intermittent and infrequent?

Edit (conclusion): The final issue was a broken solder connection on the motherboard causing the intermittent heating. The flashlight and heating issue was apparently a coincidence.

\$\endgroup\$
2
  • \$\begingroup\$ Glad to hear you found the issue and got it fixed. Thanks for following up! \$\endgroup\$
    – Bryan
    Commented Sep 10, 2022 at 3:06
  • 1
    \$\begingroup\$ Yeah, that was a fun one. The problem recurred so infrequently that I thought the best way to handle it was run a pair of wires (safely!) out to a voltmeter, teaching everyone how to turn the voltmeter on, and saying 'When it doesn't heat, tell me what the number on the meter was!' That helped me rule out sections, eventually leading me to the issue. Though a younger me may have seen the broken solder joint much sooner. Thanks for your advice. \$\endgroup\$
    – kackle123
    Commented Sep 13, 2022 at 17:15

2 Answers 2

Reset to default
3
\$\begingroup\$

The humming noise while the magnet was attached was probably due to a change in mechanical resonance frequencies, or just the flashlight buzzing against the panel.

I keep a powerful neodymium magnet (1cm^3) on my microwave right next to the magnetron to quiet a humming noise and my microwave has been fine for years.

On a tangential topic I have a bunch of magnetron magnets stuck to my furnace to dampen the panels and quiet it down too.

\$\endgroup\$
1
  • \$\begingroup\$ The flashlight buzzing makes sense. The heating issue (not seen in 43 years) would be a wild coincidence. I guess I'll see! \$\endgroup\$
    – kackle123
    Commented Jul 13, 2022 at 20:50
1
\$\begingroup\$

Damage is unlikely. If a microwave could be damaged that easily, there would be warning labels. That magnet isn't that powerful. The magnetic field falls off rapidly with distance. And, the metal case shielded most of the magnet field from the other side.

If you are curious, you can get a magnetometer app for your phone and experiment. Just don't put a strong magnet very close to your phone, the phone would more likely be damaged than the microwave.

Any change in your microwave behavior is a coincidence IMO.

\$\endgroup\$
1
  • \$\begingroup\$ That's what I was thinking/hoping. \$\endgroup\$
    – kackle123
    Commented Jul 13, 2022 at 20:49

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.