microwave Lamp, fan, carousel stopped, Sunbeam microwave

[Steve Yousten]

OK, I don't have model information handy, but this is so textbook I thought I'd start a thread and see where it goes. 

I've got a trusty 14 year old Sunbeam-branded (but Sunbeam has told me they never carried parts for it) microwave that I bought at Target.  Yesterday it worked fine.  Today the fan, lamp, and carousel have all stopped.  Clock still works.  Timer still works.  Settings still work.  It still heats food.  But the fan, lamp, and turntable no longer work.  Last time I used it, all were fine.  Today none work. 

On more tidbit:  I confess that I let the interior get pretty dirty.  And there's a few places where the finish is worn through to bare metal--but never any sparks or anything. 

So I'm thinking a fuse or connection that controlled these three systems has failed, but cursory searches yesterday said something about something called a "smart board."  Any thoughts? 

So far I haven't tried opening anything up on it to look for component access--there's a big "DANGER: ELECTRIC SHOCK! YOU COULD DIE!" sign on the back, but I don't know if microwaves have capacitors or if this is just for the kind of people that stick forks into plugged-in toasters so I didn't get too involved. 

[LI-NY Tech]

Without a model number everyone is just guessing.  

Considering that Sunbeam microwaves sell between $40 and $100 in any kind of practicality context it just makes sense to replace it, a repair will almost definitely cost more than that.  If you just want to do it as a project we need the model number.

Even with the model it may be hopeless, I don't think there is any Sunbeam tech info available.

[johntech]

Without the model number we can't look up wireing diagram. I can say that on most microwaves the safety devices are set up on the heating components not the lights and turn tables. You need to check for power to the light and to the turn table motor if you don't have any power to them then you most likely need the control board but if they never sold parts for it then it's a disposable machine. Normally control boards cost 100-200 dollars  as much as a new microwave. 

[Steve Yousten]

Thanks guys.  I'll have a look for the model information.  But as a friend on Facebook pointed out, while it might be fun to fix on principle, I'd likely wind up with a 14 year old microwave for the cost of a brand new microwave.  Yeah, years ago I broke the glass turntable.  Contacted Sunbeam and got some kind of song and dance about that they just put their name on some microwave for Target and they didn't sell any parts for it.  Eventually I took a chance on a product that looked right and had the right dimensions that wound up being the right part--even though the FAQ from the seller explicitly said it wasn't compatible. 

[Steve Yousten]

OK.  Model is a SMW770.  Sunbeam brand, manufactured by Curtis.  Found the user manual online and I'm seeing if that's actually got anything useful in it.

[Budget Appliance Repair]

Your going to have to find the wiring diagram, (good chance it will be pasted to the inside of the outer wrapper).  Then find what is common about all three things not working.

Most likely you are going to find that one relay on the board controls the lamp/fan/carousel - if that is the case then it's going to be a bad board, (not going to be worth repairing if you can even find the correct board for it).

If you determine that a relay on the board is causing the problem and you want to try to fix it cheap and know how to solder and de-solder components you might want to source a replacement relay and try replacing it.  The relay itself may not be the problem, it could be the relay coil driver circuit on the board, (you would have to check if the relay coil is getting it's required voltage - usually 12 VDC or 25VDC printed on relays when it is in cook mode and running).

[Steve Yousten]

I "fixed" it.  Slightly embarrassing but somewhat amusing story follows:  Since it doesn't sound like there are any capacitors or anything that will fry me if the device was unplugged, and I'd be replacing it one way or another, I decided to see if I could find a loose wire or something.  But I hadn't gotten around to it and wanted to nuke something tonight.  Since, again, I'd likely be buying a new one, I just used it and risked it overheating or something.  Then something interesting happened--the light came on for a split second. 

After the first run of cooking, I manually turned the drive axle for the carousel and banged on the case on the inside and on the sides.  Fixed. 

If you'll remember, I said I'd let the inside get dirtier than I should have.  I suspect the motor, fan, and lamp are all on the same circuit and not having enough juice to turn the jammed carousel caused the lamp and fan to also fail.  On top of that, the loud buzzing was not the magnetron cooking (that I hadn't heard before because of the fan noise).  In retrospect the loud buzzing was the carousel motor, trying to overcome whatever was gumming up the works.