I have a Panasonic NN-C980-B its been making a buzzing noise for a couple seconds when the microwave first turns on. it seems to work properly besides that. the other day it made a noise and then smells of burning components came out of it. but again, it still worked ok.
Today I opened it and all I noticed that there is a Zener Diode burned up. ZD703 is burned and beside it is ZD704. The solder joints of the main transistors look a little tired so I'll clean them up but do you know what these Zeners are so I can replace them?
All:
I have a 2003 Sears Ultra Wave microwave 721.63682300 with a similar problem. A few months ago it started giving off short buzzes when turned on. That stopped but then I noticed that everything took twice as long to heat up. After quite a bit of teardown&inspection I found a circuit break in the inverter board leading to ZD704 diode (pictured). I will now try to find a replacement diode to see if replacing will fix it. Thanks for your postings.
Joust:
You may want to trade out the board at this time. When you start finding multiple problems on your board the economics of piecemeal fixes start to overwhelm. The price of your 10V Zener 0.5W pn AEDZ10ES2T1 cost me less than $2 for one (I could buy 400 in bulk for less than 5 cents each) but the cost of shipping/handling was $7.50 for that diode the size of a pinhead. But you'll note from the picture I posted that a transister is also cracked; not shown was some scorching of traces. When you see multiple problems, you're likely to have more that you can't see. For me, the economics at that point dictated that it was cheaper to replace the whole board, a bit over $100 in the end. After one month, no noises, normal power, no error messages. Good luck.
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I have a panasonic convection/microwave. Last night, after I cleaned it, using oven cleaner on a sponge, it made a loud humming noise after running on microwave for about 10 sec. It does not make the noise when using the convection oven. I don't know if any heating occurred during the brief time before the humming started. Is there something that got wet and needs to dry out, or needs cleaning? What might be wrong? Should I try using it again, or would that make the problem worse?
That's good that it worked for you! Ya it's kind of hard to find out where it's coming from when you don't want to get close to it. As long as it's working and the fan is running to keep it cool, you'll just have to se what happens!
In most cases, this is a problem with the inverter or a bad magnetron.
Due to the lethal voltages used and produced, I do not recommend that an inexperienced person work on these.
I would recommend that you contact your nearest Panasonic-authorized servicer. You can find one here:
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the diode in question is a tiny zener. it is about the size of standard glass 1n4148. It is not connected to any heat sink. the board is a little burned and the solder connections on the main components connected to the heat sink look overheated. I'm wondering if it was merely a heat issue initially. I'm in ottawa too. maybe I can show you the board :)
the mag measures open. Yes the zeners are on the inverter board. sorry for not making that clear.
i did find a schematic on scribd but its not exactly the same...http://d.scribd.com/docs/11nt6gyhx8hucv9...
do you think you could tell me the voltage of these zeners? I'll swap them and hopefully with clean solder, it'll work fine. the buzzing sound is almost surely coming from the inverter board. but i didn't want to stick my head too close :)
this schematic has an accurate depiction of my inverter board.http://www.eletrodomesticosforum.com/dow...
Its a 10V zener. 0.5W pn AEDZ10ES2T1
i replaced the Zeners and replaced the solder on all of the Large transistors.
its still works but the buzzing noise is still there. the buzzing is only in the first second when the Magnetron is turned on and off.
when its running it sounds normal.
I sent a note to the Panasonic Service Depot to get a price on a new Inverter Board. I'll run this one till it pops and just replace it.
thanks.
I looked a little more at that particular model and it has the inverter board I see. That's what I assume the zener is on. Not sure what to tell you. I'm surprised it didn't come up with a error code but then again about all that would tell you is there is a problem with the board but nothing specific. Sometimes when the mag shorts it takes out the inverter. I would measure the mag leads to ground and they should be open or 20M or so. If you have both a mag and inverter bad it's probably time for the bone yard. I live in Owatonna MN.
where is the diode fried? Usually a buzzing sound like that comes off the high voltage diode by a tin can capacitor. one side of the diode is connected to the case. Is that what it looks like?
my board finally popped.
the transistor Q702 blew. its a 1M30D the rest is hard to read because its burned off. can anybody confirm?
I looked online and cannot find info on this transistor. anybody have a cross refence for it? it appears to be a BJT. the board is labeled with an E for emitter.
Munson1 - did you notice that you have a crack in C703?
my inverter board finally blew. transistor Q702 burned up. it seems to be a 1M30D the rest is burnt off. can anyone confirm?
is there a cross? I cannot find info online for this transistor. I assume its a BJT as the board has E labeled on one pin.
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