What Should I Do With This Microwave Oven?

[fine-tune]

I think I've got the largest "portable" microwave oven ever made!
Its a big, heavy box with a 2 cu.ft. capacity. I purchased it from
Sears less than a year ago. Generally I don't pay for the extended
warranty, but the few times I have it paid off. I recently replaced
a $250.00 drill that failed after 18 months. They gave me a new
one immediately, because I had the extended warranty.

Without telling me, Sears changed their extended warranty policy.

The control board piezo speaker failed. All other oven functions are
working, but it seems kind of creepy that there is no sound at all from
the control board.

Sears told me that they no longer replace the appliance. Instead,
it's sent out to be repaired! At least three or four weeks, I'm sure.
They said I could "rent" a microwave and they would reimburse me
for the rental charges. If I wasn't so angry, it would almost be funny.
In effect, they have voided these extended warranties.

I've repaired microwave ovens before, but problems with the control
board can be expensive. I'm looking at Homer Davidson's Microwave
Oven Repair manual. He calls the microcontroller a microprocessor.
Microcontrollers interface with the real world and perform a function.
Controlling a relay, motor, buzzer, or almost anything you can think of.

The question is, has the piezo element failed or is it the oscillator driving
the speaker? If the oscillator, which is integrated into the microcontroller
has failed, then a repair would involve replacing the entire board. Much
too expensive.

Since all other oven function work, the piezo element may have failed.
That would would be a cheap fix.

The model number is 721.66469500

Does someone sell a generic buzzer for microwave ovens? It probably
doesn't matter if it fits the board perfectly. Extending the leads from
a generic buzzer so it stands off from the board shouldn't cause any
problems.

[MrAl]

Hi there,


Maybe you worry for naught...

My oven has a turn off mechanism, so i can shut off that darn beeper. That thing is nuts,
and i hate it so i turn it off. It comes back on if the power goes out, then comes back on,
and i have to reset it again to turn it off.
If i were you, i would not complain it's a good thing

What do you need this for? If it is only for when the oven is 'done' then you can install
a cheap current transformer to sense current to the oven from the 120vac line, then
trigger a buzzer. This would be so easy to build, and you wont have to fuss with the
internal circuitry. If you need help designing this i dont mind lending a hand.

If you insist on fixing the internal part, you can check the signal getting to the piezo element
if that is in fact what it is. If it is getting the signal then the element must be shot. The
only thing is you should get one the same size so the power rating is the same.
If the signal is not present, it could mean something on the control board burnt out.
In that case you may have to go with the current sensor outlined above.

[reloadron]

Since everything works with the exception of the buzzer I would venture a guess that only the little buzzer has failed or possibly a victim of a poor solder joint that has failed. Buzzers of that type can be had pretty easily. Personally I would first remove the element and place a small voltage across it like 3 to 6 volts and see what it does. Look for a part number on it to see exactly what it is.

Many use a device like this:


Similar to what you find on a computer motherboard. Some are just a simple buzzer device.

I would just open the thing and see where it is and what you have in there.

<EDIT> MrAl was quicker than me. </EDIT>

Ron

[fine-tune]

I understand your feelings completely, MrAl.

I've disabled buzzers and beepers in a couple of cars because they
were driving me nuts!

For whatever reason, I like to hear that brief "beeeep" when I press
a key on the control board. Let's say you're setting the timer for 60
seconds. If the speaker is working, I don't have to look at the display
when I press "6" and "0." When you think about it, that little "beep"
is really an important part of the control board. It doesn't just sound
off when a timing cycle is completed. These soft touch membrane
switches on most control boards need that extra "beep" to varify that
the switch made full contact. A microwave oven is a major appliance
that draws a lot of current. I like to know I set the various timing
cycles correctly. That's why that little "beep" is important to me.

All I know is, I paid Sears for the extended warranty. They're suppose
to give you an immediate replacement, or at least order a replacement
for you if it's not in stock. I'm usually a very passive kind of guy. I felt
like screaming to everyone in my local mall that I was ripped off by Sears!

[Bob Scott]

Sears has, or used to have, the policy "Satisfaction guaranteed or your money refunded."
I have heard of Sears refunding money to furniture customers even though the furniture was 3 years old. That was circa 1983. Give them a call and ask Sears Customer Service if they still have the same policy. Tell them you are not satisfied. Let them know that you might contact the local consumer ombudsman from the local newspaper to have your complaint made public for all to see.

[MrAl]

Hi again finetune,


Sears is a little strange to me, that's why i dont shop there too often. Once in a while if they have
something special i want i might shop there online.
I was gong to get a new mattress there one time and it was a good price, but then i found out they
wanted 60 dollars to deliver it, and whats more is that they would not let you go there an pick it up
either. That was the end of that.
On the other hand, i ordered quite a few clamps from them online and when i went there to pick them
up i found that they had a 20 minute wait policy, that you get 10 percent off if they dont get you the
product within 20 minutes. Now 10 percent isnt that much, but they do get it for you pretty fast so
i was out of there with the clamps. Ditto with a special meter i ordered from them, again online and
went to store to pick up.
That was a while back though, maybe two years.

If they really do owe you then you just have to be firm with them. You have to state that they
owe you more than what they are giving you and make sure they dont try to get out of it.
Stores will do things like that these days.

[denkiguy]

The piezo "buzzers" (I prefer the term "sounder") used in consumer products now a days are fairly generic. They are like speakers with a really peaky response curve in the 2 to 3 KHz range. Typically, the microcontroller drives the sounder with a square wave around 2 KHz to make the peep sound.

If you want to try to replace it yourself, you can find a reasonable selection of Piezo Buzzers at Radio Shack. You might find that the replacement buzzer has a different resonate frequency than the original which will result in lower volume.

[jimmy101]

Like others have said, the most likely problem is a bad solder joint. Either on the PCB or internal to the piezo where the wires connect to the substrate. Other than the internal solder joints, Piezo are pretty robust little devices.

You should be able to replace the piezo and I would expect that just about any piezo would work with fairly little chance of hurting anything else. Any piezo made for PCB mounting is probably designed to be driven by something like a uP.

The only real issue is whether it is a simple piezo transducer (just a piezo element) or if there is some circuitry in the case, like an oscillator so it can operate from a DC source.

As to the Sears warranty, the only thing that matters is what the paperwork actually says. It doesn't matter what they used to do or what they used to promise to do.

[CeaSaR]

For your sleuthing purposes, just connect a small speaker to the pads of the piezo and listen for the beep.
You should hear something if the signal is good. Then check the solder joints as mentioned in above posts.
Fix as you see fit.

As for the extended warranty, read it very carefully, paying attention to what it actually offers and looking
for any disclaimers saying it (the warranty) may be changed without notice. If the offer is to replace it and
there are no disclaimers, they are legally obligated to do as the warranty says. Also, make several copies to
keep 1) at home, 2) on your person when you go to dispute it. Never let them take the original, offer them
the copy should they want to "copy the original". They wouldn't need to do that anyway because it is to be
on file with Sears somewhere. You do not have to provide the paperwork, they must produce it. That way, if
you need to go further, you have the original for court purposes.

Good luck,

CeaSaR

[haklesup]

Just about every warranty I have ever seen has boiler plate text to the effect that they will "Repair or Replace at the companys discretion" furthermore, its pretty standard for shipping to be paid by the consumer (to the repair facility at least).

With that said, Sears tools generally get a better warranty treatment than any other product except perhaps sears brand clothing which is always for replacement. The sears lifetime replacement tool warranty (where applicable) is what sells that product over other quality (read not chinese) brands.

In any case FWIW, My sears microwave beeper has been going on and off for months. My roommate tells me her daughter is doing it but I have yet to find out how (i.e. pull out the manual and RTFM or ask). In your case, unplugging for a minute and seeing if it will reset the beeper is too easy not to try.

A warranty is a contract, depending on what state laws are, they may not be allowed to modify it in any way after the sale is closed. Though they can give better service at will, don't expect it every time.

[MrAl]

Hello again finetune,


I just wanted to mention that as you know i keep my buzzer turned off all the time, and never use it,
so what i do when i want to set the timer is i press all the buttons that i need and then after that
look at the display to see if the correct number had really been punched in. 9 times out of 10
(or better) the correct number is displayed.
Also, you can type repeated numbers for many times instead of trying to punch in the exact time.
For example:
instead of 100 type 111 (just all 1's) for 1:11 instead of 1:00,
instead of 200 or 230 type 222 for 2:22 instead of 2:00 or 2:30,
instead of 330 type 333 (only 3 seconds difference)...
Get the idea?
As the time gets greater the difference is a smaller and smaller percentage too, as in trying
to set 11 minutes:
instead of 1100 type 1111 for 11:11 instead of 11:00 and that's only 11 seconds out of 11 minutes off.

I find this works for a lot of time values and after a while you do it without even thinking.

If you want closer times, you can repeat just the last two numbers as in trying to set 2:45,
instead of 245 type 244 and that's almost the same.

It gets easier and easier the more you do this too. I never type in the exact time anymore

About the oven current draw:
Im not sure if you meant that the oven draws a lot of current so you dont want to interrupt that
with a sensor, but if so then i just want to say that a current transformer drops almost no voltage
at all yet is able to sense the current, and also provides for line isolation so your detector circuit
is not exposed directly to the line potential. BTW i did this for years with my mic.

[haklesup]

Another comment on extended warranties. The original 1 year (or whatever) is the manufacturer warranty. That means if Sears has to do something, they charge it right back to the vendor but in the extended period its all their responsibility so often extended warranties (especially by smaller vendors) are very hard to execute and you sometimes need to demand they be honored. Sears probably won't make you work that hard though since they are very large and have their own service sub-unit.

I generally advise anyone with technical talent to skip the warranty. Of all that I have bought in my lifetime, none have ever been used (even for cars).

[Lenp]

Years ago I replaced a ton of magnetrons and HV diodes in mw ovens. Today for the most part they are no-fixum's! The local discount store has a shelf full of ovens for under $60 so for most units if it's out of warranty, it's junked. My present oven is a Sharp that had a display fail just days out of warranty. Wholesale parts cost is $75 so it didn't get changesd! Usually we set the timer correctly, if done with some care, except when I unknowingly went into the charcoal briquette and smoke detector testing business when I made bagel briquetts by setting the timer for 30 minutes instead of 30 seconds.

Len

[Bob Scott]

My microwave is still the Amana Radarange with "touchmatic" controls that I bought in Fargo in 1978. It has never needed service. Thirty two years old, it is used at least 20 times/day, minimum. It's built like a tank, only stainless steel.

Of course it costed way more than $50, an embarassingly mindboggling huge amount.

[Robert Reed]

My Panasonic gets heavy daily use and is going on 27 years old. The only parts I had to buy for it was a magnetron and antenna motor. But it never needed the magnetron. In my cockiness I quickly and falsely deduced the Magnetron was bad and after tearing it apart and replacing it, I discovered the antenna motor was the culprit - a $10 device. I wasted $48 on a good magnetron but the upside is I purchased the oven for $85. I think thats a pretty good track record. Now I am wondering what project I could use a good Magnetron for?