Wanted: Appliance / household wiring experts

[Glinda]

Originally Posted by Clodfobble

Do not continue to use that microwave. Throw it away immediately.

Think about it this way: even if it was caused by an errant power flicker, or a cat's stray paw, those situations could happen again in the future. What's more, if you have an electrician look at the internal wiring, the only way you'll know for sure if the repair worked is if ten years go by and your house still hasn't burned down. If you're wrong, you'll find out the hard way--and if it happens at night, you could die from smoke and carbon monoxide inhalation before you ever have a chance to wake up to see the danger.

Your life and home are not worth saving $60 on a new microwave.

*pout* You're right, of course, but shit.

And it's not about the money; it's about stupid new stuff with stupid programming. Does anyone make a microwave these days that doesn't force you to fuck with defrosting food every 60 seconds?

[monster]

Originally Posted by Glinda

*pout* You're right, of course, but shit.

And it's not about the money; it's about stupid new stuff with stupid programming. Does anyone make a microwave these days that doesn't force you to fuck with defrosting food every 60 seconds?

yes. but..... it's better/faster if you rotate it.......

[Happy Monkey]

Originally Posted by Glinda

And it's not about the money; it's about stupid new stuff with stupid programming. Does anyone make a microwave these days that doesn't force you to fuck with defrosting food every 60 seconds?

One with a turntable might not?

[monster]

Originally Posted by Clodfobble

Do not continue to use that microwave. Throw it away immediately.

Think about it this way: even if it was caused by an errant power flicker, or a cat's stray paw, those situations could happen again in the future. What's more, if you have an electrician look at the internal wiring, the only way you'll know for sure if the repair worked is if ten years go by and your house still hasn't burned down. If you're wrong, you'll find out the hard way--and if it happens at night, you could die from smoke and carbon monoxide inhalation before you ever have a chance to wake up to see the danger.

Your life and home are not worth saving $60 on a new microwave.

this.

[sexobon]

Power outages can be preceded by power surges and the old microwave may no longer be able to handle the surges even though the amperage rating for the house wiring and circuit breakers/fuses can.

[Glinda]

Originally Posted by sexobon

Power outages can be preceded by power surges and the old microwave may no longer be able to handle the surges even though the amperage rating for the house wiring and circuit breakers/fuses can.

Ah. Now this makes perfect sense to me. I was sure there was a house wiring component to this mystery. Thank you!

[tw]

Originally Posted by Glinda

Ah. Now this makes perfect sense to me. I was sure there was a house wiring component to this mystery.

No house wiring is involved in this mystery (if AC electric lights do not flicker or change intensity when major appliances power cycle). Posted were electrical fables invented by many who forgot to first learn how electricity works.

If you had a surge, then a microwave is damaged - no longer works. And some of other less robust appliances (ie GFCIs, clocks, central air controller, door bell) are damaged.

Not one reason is given to suspect house wiring or a surge. So those wild speculations are binned immediately. Honest replies also say why with numbers.

We even saw this once in a factory where a toxic gas (phosphine) was vented into an area of construction workers. Fortunately a bird fell dead before those construction workers got too close. That is when I was brought in.

Sometimes power does not fully turn off or on. Intermittent and quick AC offs and ons cause DC voltages to vary to intermediate voltages. (What glatt calls a power flicker.) Computers that run on 5 volts get disoriented when that voltage is below 4.8 and does not fall to zero. Then the computer can start babbling; executing code that makes no sense.

In our case, a babbling computer powered open every valve venting a large tank of toxic gases. In your case, it simply instructed one relay to close and stay closed.

Your PC is not a real time computer. So it does not need this major human safety device. That computer inside a microwave is real time. So a watchdog timer literally creates a heartbeat. If the real time computer does not issue the proper heartbeat every few milliseconds or seconds, then a watchdog timer cuts off power to everything.

But back then, despite even telling this to some people's face, some so called designers would ignore the warning and not implement that watchdog. Or would write code in a manner that even a babbling computer would still act as if functioning properly.

In short, your microwave either does not have or did not properly implement a watchdog timer. So quick AC power interruptions caused a babbling computer chip to power on the microwave with nothing to time it (power it) off.

Can we say that with certainty? No. Do you have symptoms to justify that event? Yes. Did anyone support their conclusions with the always required reasons why and perspective? Obviously not. So this is your only possible answer that has any credibility.

Back then, watchdog timers were typically separate chips provided by companies such as Dallas Semiconductor. Today, that essential human safety function is standard in all single chip computers.

And yes, this many decade old (that well understood concept) is clearly something new to you and others. So understand it will require at least three (or more) rereads. And maybe only after asking a few questions.

[glatt]

So you are saying the power fluctuation caused it, and the microwave has always had this problem? It's as good today as the day it was new. But it will likely happen again if the power fluctuates in the same way in the future?

[tw]

Originally Posted by glatt

So you are saying the power fluctuation caused it, and the microwave has always had this problem?

Not any power fluctuations. A list of different anomalies under that category are many. This one type fluctuation is why a watchdog with voltage monitor exists. And why some computers and games also have a safety lockout feature.

Other speculated anomalies (ie a surge) do not explain those symptoms. For example, if power on was created by a surge, then that oven would remain always powered when plugged in. Fact that it worked normal after power cycling implies a problem often found with real time single chip computers of that vintage. And not something created by a mythical surge.

If a cat started it, then that microwave eventually timed out. Or a thermal safety monitor cut off power. Unlikely a cat can just happen to hit a right sequence of keys. Or even has sufficient paw strength to depress those keys.

Provided was enough information to provide relevant facts - to define the defect. Much later comes a solution - which typically does not involve trashing a microwave.

Little facts, such as the above requested behavior of incandescent bulbs, is significant information. Also the state of other household appliances would say more.

BTW, when one only understands how to 'wreck shit', then even "electronic rust" is proof that Martians are conspiring with the Rovers to kill us all using our microwave ovens. Since extremists tell us those also used processor chips of same vintage design. He would accomplish more writing for Marvel.

[sexobon]

Originally Posted by Glinda

Ah. Now this makes perfect sense to me. I was sure there was a house wiring component to this mystery. Thank you!

Originally Posted by tw

No house wiring is involved in this mystery (if AC electric lights do not flicker or change intensity when major appliances power cycle). Posted were electrical fables invented by many who forgot to first learn how electricity works. ...

If you read what was written, with comprehension, you'll see that no one was blaming house wiring for the malfunction.

Originally Posted by tw

… If you had a surge, then a microwave is damaged - no longer works. And some of other less robust appliances (ie GFCIs, clocks, central air controller, door bell) are damaged. ...

False. That's only if there's a large surge:

Why worry about power surges?

Your home is filled with items susceptible to power surges. Anything containing a microprocessor is especially vulnerable - the tiny digital components are so sensitive that even a 10-volt fluctuation can disrupt proper functioning.

Microprocessors are found in hundreds of consumer items, including TVs, cordless phones, computers, microwaves, and even seemingly "low-tech" large appliances like dishwashers, washing machines and refrigerators.

Large power surges, as with a lightning strike, can cause instantaneous damage, "frying" circuits and melting plastic and metal parts. Fortunately, these types of power surges are rare.

Originally Posted by tw

… Not one reason is given to suspect house wiring or a surge. So those wild speculations are binned immediately. ...

Again, no one said they suspected house wiring was the cause. As for there being no reason to suspect a surge - False:

Internal power surges

More than half of household power surges are internal. These happen dozens of times of day, usually when devices with motors start up or shut off, diverting electricity to and from other appliances.

Refrigerators and air conditioners are the biggest culprits, but smaller devices like hair dryers and power tools can also cause problems.

External power surges

An external power surge, stemming from outside your home, is most commonly caused by a tree limb touching a power line, lightning striking utility equipment or a small animal getting into a transformer.

Surges can also occur when the power comes back on after an outage, and can even come into your home through telephone and cable TV lines.

And then there's a potential problem from cumulative damage that can make a very old microwave more susceptible to a small external surge before or after a power outage:

Low-level power surges won't melt parts or blow fuses, but they can cause "electronic rust," gradually degrading internal circuitry until it ultimately fails.

Small surges won't leave any outward evidence, so you may not even be aware they're happening - even though they may occur dozens or even hundreds of times each day.

Obviously, tw has acquired "electronic rust," which gradually degraded his internal circuitry and it is ultimately failing … not one brain left in his poor old head.

[Glinda]

Heh. That's what he said.

[monster]

Originally Posted by Glinda

Heh. That's what he said.

and did the rotation happen?

[Glinda]

Oh, you betcha.

[xoxoxoBruce]

Bought a Sharp in 1973, big sucker with the carousel and knobs, for almost $500. It lasted 25 years and 1 month.
Replaced it the same day with another Sharp, I think it's 1.8 cubic feet, big power, carousel, buttons for auto-defrost, auto-reheat, popcorn, potato, so easy even I can do it, Less than $150.

Plus I have a spare glass carousel plate in case I break it.
And used the carousel turntable drive with a small platform for spray painting objects 360 degrees.
You can use the unplugged one as a kitten proof bread box.

[glatt]

Power flicker probably caused the microwave to turn on suddenly, spooking the cat, and causing it to knock over the trash.

If the microwave seems to work fine now, I would also have a hard time tossing it. But it's the smart thing to do. You WILL get another power surge in the future.