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Old 03-06-2022, 08:50 PM   #21
redwire
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Default Re: Microwave started making rapid clicking sound and smoke

Relays typically must operate given 70-75% of their rated coil voltage, so 13.5V minimum spec. If you hear it click with 12VDC, that's good enough, we just want to see if the contacts are pooched and that is where the arcing occurs.
It's low current the coil, 20mA so even two 9V batteries could be used.
Careful not to remove a fan relay and then operate the oven, it needs airflow.
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Old 03-06-2022, 10:40 PM   #22
Widget
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Default Re: Microwave started making rapid clicking sound and smoke

Hey Red, thanks for the info

I did a rough wiring to the relay, connecting 12v from my PC psu ans 12v car bulb. Seems ok. There was a little crackling but I think that was due to poor contact with the power-in in the leg of the relay.

I thought about swapping relays with the fan, just to see if the fan still works, but maybe I don't have to if the relay seems to be working?

Everything on the board seems dry. The only other testing I can think of doing is,

1. Testing with a incandescent bulb sam_sam suggested,
2. Plugging it all in, power on, and start checking voltages

I don't know what to do about the buttons not working correctly though. Heck, for all I know it's a completely unrelated issue and became like that long ago (I rarely used those numbers, usually just hit start or preheat at lower temps).

Here's a video of the relay test. Sorry about the hand and background chatter.

https://youtu.be/zAG3H-k7hQA

Last edited by Widget; 03-06-2022 at 10:43 PM..
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Old 03-11-2022, 05:54 AM   #23
Widget
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Default Re: Microwave started making rapid clicking sound and smoke

update: Microwave is working. I put it back together, and buttons seem ok. Convection oven preheats ok too. Not sure what when wrong with the keypad, perhaps ribbon cable wasn't aligned or had some dirty contacts.

I tried connecting the bulb to the transformer wires as suggested (to check relay) but nothing happened. As of writing this, it came to mind perhaps it would have only engaged the bulb if the convection was activated ?

Other than that, all seems ok for now.

Thanks again for all the suggestions, much appreciated
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Old 03-11-2022, 03:05 PM   #24
sam_sam_sam
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Default Re: Sharp R-990K Microwave started making rapid clicking sound and smoke

You have to set an amount of time like you would if you did not have the incandescent light bulb instead of the transformer
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