Grassroots Microwave Repair

Hey All,

My maybe-a-year-old Panasonic microwave model NN-SC668S has just kacked, thereby making yummy leftover warming a bit harder than it needs to be at this juncture.  It will run for about 20 seconds then go dead. Even the display goes blank.  When I remove and replace the power plug back into the outlet, it will blink back on.  when I try to run it again, it will last about two seconds then blank out.  Subsequent attempts result in hearing the internal circuit breaker cycle itself.

Luckily, I am surrounded by appliance parts places, plus the interwebs,  I just need to know what it is I'm replacing and whether I can get one.  Any guidance (including pointing to interweb tutorials) would be greatly appreciated.

Thank you,

Jerry

Not an appliance expert, but I looked at fixing one once. It's been years, but I recall something about a really powerful capacitor which could electrocute you. 

Proceed with caution.

I replaced the big capacitor in mine after my mother-in-law thought she set a 30 minute timer, but instead turned on the empty microwave on high power for 30 minutes. 
 

Yours has different symptoms than mine though. Between online appliance repair places and youtube, you should be able to repair. 

Ifixit.com helped me diagnose and replace the door switches on mine when it kacked.

Worth a look, but I suspect that it's a power supply problem and that there is a board, or possibly a component therein, to replace.

I'm not leaning towards the big power capacitor because that's usually there to provide a start-up kick of extra juice to get the thing going.  It gets going.  It doesn't stay going.

Actually, the big sticking point is the need for an anti-tamper T-15 Torx bit.

Harbor Freight has the whole set for cheap.  Or you can take a small punch and knock out the center anti-tamper thingie, then use a regular torx.

Dr. Hess said:

Harbor Freight has the whole set for cheap.  Or you can take a small punch and knock out the center anti-tamper thingie, then use a regular torx.

I bought quite a few because the Glendale Sears is no more and they closed it out.  So I don't want to buy a whole set.  Intrigued by the punch idea except it's a sheet metal box and I wouldn't want to turn it into a trapezoid by banging the crap out of it.  I'll find one.  If I don't, it's punch time.

I've been in that Glendale Sears a few (hundred) times.  And the K-Mart that was on the south end of town.  I think I still have a 3/8" socket wrench I bought at that Sears over 40 years ago.  And a couple screwdrivers.

The HF security bit set is only ten bucks.  https://www.harborfreight.com/security-bit-set-with-case-100-pc-68457.html

They also have a tool just for the torx kind for $7: https://www.harborfreight.com/7-pc-star-tamper-proof-key-set-97471.html

Of course, they cause cancer in California, so watch out.  The rest of us are safe.  My technique for busting out the center thing is to take a punch, like 1/8" punch or so, and set it against the center stud at as great an angle as possible, then wack it with a ball peen hammer.  They break off pretty easy, actually.  That's how I used to to them, but since gettng the right tool bits, I don't bother anymore. 

The K-Mart was gone around '05.  The Sears succumbed for good on 3/17.  We were able to purchase some material handling equipment from their warehouse for her home staging business.  We got a nice long rolling cart and two rolling stairways for maybe ten cents on the dollar. In the meantime, someone will have that bit.  I'll find one tomorrow.

There used to be a Chinese tool store on Brand Avenue in down town.  OK, OK, that was 35 years ago. Maybe more.  I still have a very large Crescent style adjustable wrench from there.  15", if I recall, and opens up to about 2 inches or more.

Went to the future hammer store and bought the security fastener bit set for $6.99.  The kit allows me access to almost any type of security fastener now in use.  Especially important because my wife's warehouse has restrooms with stalls and other fixtures loaded with them.  Best of all, there's very little overlap with anything I already own.  Now let's get that nuke cover off.

......Aaaaaaaaand we're back.  Took the cover off.  First thing I noticed was the complete lack of any large capacitor.  The mount was there (they went through the trouble of installing it) but the wiring harness bit and the capacitor was capacitor non grata.  I inspected the magnetron for any physical damage like burn marks or melty spots but everything was good.  Next up was the door switches.  Both passed visual and electrical inspection.  Also tested the override switch which clicks the unit off should someone be able to force the door open.

At this point, I noticed one of the main busses to the control board was a little wonky.  It's a plug with a bunch of wires going to various locations.  So I gave it a shove and it moved.  Seems like it was partially pulled out.  Made sure it was tight and replaced the cover.  Don't ever test a microwave without the cover on, especially if you're pregnant or use a pacemaker.

Put a Pyrex measuring cup full of water in there and powered it up.  Ran for 1.5 minutes (besting its previous pre-repaired record of 20 seconds) and the water heated up.  So it stays on and the magnetron works.  Fingers crossed.  We're making some good grub around here so having a working nuke makes leftover prep and defrosting much quicker and easier.

Well worth the $6.99 tool investment.  Thanks to all for your suggestions.

Ok, as the local appliance repair technician of this forum, I am going to have to ask you to step away from the tools and put down your pride. I know everyone around here can fix almost anything, but the capacitor in that microwave has the ability to fry your heart stopped, without even being plugged in! You might think that that microwave is dead, but until you discharge the capacitor, and correctly, it is a liability to you, your wife, and your children. Is a $50 microwave really worth your life?

In reply to _ :

Or you could just discharge the cap before touching it.

In reply to T.J. :

Yeah, and I suppose everyone carries the right meter to check that it is discharged right? About half the caps I discharge at work you never see an arc. 
 

furthermore, even if you get the cap discharged, the probability that you screw something up on the H,V. Side of the circuit fan mean imminent danger to all present.

Do whatever you people want. I'm just warning with seasoned, veteran knowledge I possess. We lose about 2 techs a year to electrical shock. It's always a lack of safety. 

I used to repair ship's RADAR systems.  I think they ran like 15KW or so PEP through the magnetron.  Used to have a magnet from one around here.  Not sure what happened to it.  I'm not dead yet, so safe work is possible for GRM'ers.

That HF bit set is real handy.  I use it all the time.

In reply to _ :

I know you are trying to keep folks safe. Sorry that I was a bit snarky. You are correct in that a person who doesn't have a decent handle on electronics/electricity should maybe steer clear and either get a new microwave or call a repair person. With a little bit of knowledge and common sense plus the internet I think most people who are reasonably handy and are not completely baffled by electrical theory could do a microwave repair.

I'm no pro, but I've done repairs on my dryer, my microwave, my oven, my dishwasher and my fridge over the past 7 years. I pretty much think that anything that breaks that is worth trying to save is an opportunity to learn something new.

You guys did notice where I wrote there was no capacitor in my unit, right?

In reply to Jerry From LA :

You have an inverter unit. Godspeed. 

In reply to _ :

Yeah, but it's working (there are no "fingers crossed" emojis).