Oven problem

My kitchen's electric oven is misbehaving. After it's been on for a while, it can make a buzzing noise, and its LCD (?) flickers. Eventually it shuts off, resets itself, and restarts with a "Program Cancelled" message.

Clearly, its microcontroller knows that it was previously running. This is not like a power-on reset.

The buzzing sounds a bit like a relay that's receiving so little coil current that voltage ripple makes it buzz. I've come across that before, and this thing contains several relays.

The obvious thought is dying electrolytic capacitors, but failing when it's got warm doesn't fit my understanding of such capacitors which would be expected to perform better when warm, even if they've aged to the point where they're no longer adequate.

Any thoughts?

Sylvia.

Reply to
Sylvia Else
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On a sunny day (Sat, 25 Dec 2021 22:17:48 +1100) it happened Sylvia Else snipped-for-privacy@email.invalid wrote in snipped-for-privacy@mid.individual.net>:

If you have a scope measure the ripple voltage on those electrolytic caps Also in most cases with faulty wallwarts I have seen the bad caps are a bit swollen at the top. _____ (_____|========= . / \ |

Reply to
Jan Panteltje

I've seen capacitors fail to perform when hot, somewhere near the top of their temperature range performance begins to decline.

Reply to
Jasen Betts

could be a voltage regulator going into thermal limiting?

Reply to
Jasen Betts

Thanks for the replies.

My diagnosis is a burnt-out fan motor. This fan is meant to keep the electronics cool.

Sylvia.

Reply to
Sylvia Else

The relay coils are copper, which increases in resistance by about

+.4%/°C. Relays are *current operated* devices (ampere*turns) that happen to be specified in terms of nominal operating voltage.

So if the power supply is marginal the relay might not pull in when it's warm. I would guess the capacitors are the culprit.

Reply to
Spehro Pefhany

Could still be bad caps, could be cracked/broken solder joints on the PC board, loose or intermittent cable connections.

If a replacement controller board isn't available, then an R&R of all of the electrolytic caps (use good-brand 105C or better), and inspection of all solder joints (especially those on connectors) and a touch-up of any questionable ones with proper solder and flux would be what I'd probably try.

Reply to
Dave Platt

Call an authorized repairer. They will have seen the problem before and come with all parts required for repairs.

Fast repair, no sweat.

Also, even if you are eminently qualified to do such a repair, if an insurance company wants to fight paying out (say for example, your house burns down for some other reason) they may try to say the fire started with the oven and it was your fault because you were not authorized to do the repair and did not use authorized components. It does not happen often, but it does happen.

We live in an age of compliance and legal liability not the past age of competence and ability -

Reply to
David Eather

I live in Australia. Insurers don't get to pull that nonsense here.

As for arriving with the required parts, they don't do component level repair, and it's unlikely boards are still available for this oven, which is probably more than 15 years old.

Sylvia.

Reply to
Sylvia Else

Ah, so you've determined that the fan was the cause? I take it this is an "in wall" unit, not a free-standing oven (= "range" in the U.S., with stove top). Being an in-wall type makes sense to me it needs a cooling fan. The "range" types put all the electronics in separate housing away from the heat.

FWIW, my first guess was going to be: Check the AC mains line voltage (easier than opening up the oven...) Maybe its low "brown out", due to faulty wiring or circuit breaker, or excessive loading on that branch.

Reply to
Rich S

"determined that it was the cause" is perhaps over stating it, but the fan is clearly broken, and without it the electronics bay was heating up. Jasen's suggestion that a regulator would go into thermal limiting is then entirely plausible.

It would also explain why I could never reproduce the issue with the cover off - the extra ventilation was keeping the temperature down.

I'm left wondering whether I previously just failed to notice the fan wasn't running, or whether the fault was somehow intermittent. I'll probably never know now.

Yes.

Sylvia.

Reply to
Sylvia Else

They're 'usually' pretty quiet and hidden. though they might get noisier before seizing up.

If the coil's not actually fused open, it just needs a bit of cleaning.

RL

Reply to
legg

It's a three-speed shaded-pole motor. Only the highest speed contact has continuity with common. The other two are neither connected to common, nor to each other. The wire to the lowest speed contact has vapourised, leaving a black residue.

It's not clear why that would leave the medium speed contact isolated.

Sylvia.

Reply to
Sylvia Else

The age thing is very valid.

But, I also live in Australia. This is about 20 years ago: My bestie, a technician with a trade school qualification and a Associate Diploma in electrical engineering had an insurance assessor tried to pin a house fire on his repair of a TV. He had to jump up and down and make all sorts of noises to stop that, and the fire then went down as "unknown causes" so it didn't get to the insurance company, but if my mate wasn't there and didn't put up a vigorous defense it would have. You can judge yourself if the insurance company would have tried to reclaim it's payout. Much later it came out that a child who lived at the house had been playing with candles, did something silly and was scared to own up.

Reply to
David Eather

It ultimately depends on the terms and conditions of the insurance contract, but I would be surprised if it would have made any difference to the outcome if your bestie had in fact caused the fire by way of the repair to his television. To avoid its liability the insurer would have to show, on balance of probability, that it was the intent of your bestie that the television catch fire.

It's somewhat analogous to insuring one's car against damage in a crash. While some crashes arise with a genuine lack of fault on anyone's part (sudden medical event, for example), most crashes are the result of a driver doing something they shouldn't. Only the shonkiest of insurers issue policies that only cover no-fault accidents.

As an aside, note that many car-hire contracts, including from some well known car rental contracts, have terms that exclude liability for accidents that result from a breach of the road rules, which puts those into the same group as the shonkiest of insurers, and those rental companies should be avoided by anyone who doesn't want to become bankrupt.

Sylvia.

Reply to
Sylvia Else

Here (SW USA), the previous homeowner is liable for electrical faults for a period of 5 years AFTER the sale of a property. As the oven would likely be sold WITH the house, your liability would extend far into the next owner's occupancy.

A bigger concern is not wanting to put *oneself* at risk as YOU will be occupying the place in the near term.

It is for this reason that I either do my own repairs *or* actively supervise the party doing them.

[I once had a firm replace the brakes in a vehicle. Some *years* later, had a front spindle bearing fail which rendered the front brakes completely useless (the calibers being pushed apart by the wobbling wheel). I applied the emergency/parking brake which is a purely mechanical system affecting only the rear *drum* brakes. Only to discover that they also had failed. It turns out, the reshoeing had left out the mechanical link (just a solid steel bar) that allows the emergency/parking brake to pull one shoe into the drum via the second shoe. The link was present on one side of the vehicle but ineffective owing to the slack designed into the emergency/parking brake cabling. (had the link *not* been present when the reshoeing was done, one can bet the shop would have brought it to my attention and charged me accordingly for its replacement! instead, they had simply forgot to install it)]

It wouldn't be uncommon to find a spare part for a major appliance at 20+ years, here. You might not be able to find a replacement "plastic shelf bracket" for the interior of a refrigerator. Or, the louvered control door that gates cold air into the refrigerator compartment from the freezer. But, you'd find an icemaker, compressor, etc.

Reply to
Don Y

Don WHY does this fool exist wrote: =============================

** Only if it can be proven they were responsible for them and serious harm was the DIRECT result. Being " not immune " and being * liable* are not the same thing.
** Hypothetical bullshit.

** Bet they f****ng hate that.

** It wouldn't be uncommon not to either. Particularly PCB boards.

...... Phil

Reply to
Phil Allison

A neighbor had an electrical fire in her automobile, parked out front of her house. The city FD came to extinguish it. And, did so.

Some hours later (after bedtime), the fire reignited. Turns out, the FD never disconnected the battery so the ignition source was still present. Car burned. Along with the *entire* house (one of the few wood-framed in the neighborhood).

Didn't take much effort for her insurance company to eek out these facts.

And, the city to pay to *rebuild* her home! (eery feeling seeing an empty, charred slab... and then the original house BACK on it!) I wonder what would have happened had she (or another neighbor) lost her life in the blaze?

Any real estate transaction, here, (legally) requires the seller to disclose ALL "material" facts about the property that could be seen as affecting its value, or potential hazards (liabilities) going forwards.

It is not possible to avoid the disclosure with a /caveat emptor/ clause. I.e., an "as is" sale simply says "Seller isn't going to fix/upgrade the items that should otherwise be fixed/upgraded". But, IT DOES NOT ABSOLVE YOU FROM THE DISCLOSURE REQUIREMENT! The disclosure is required even if the buyer fails to ask.

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There are additional requirements placed on issues that the buyer *does* inquire about! So, if you answer "Are you aware of any PAST or PRESENT (emphasis mine) problems with any built-in appliances? Explain:" with anything other than "No/None", the buyer can ask you to elaborate on your answer and you are obligated to "disclose the information, even if you do not consider the information to be material".

Failing to disclose something you KNOW about leaves you liable for that

*fraud*. Which means, buyer can sue to be "made whole" for consequences of your omissions/misrepresentations. "My house burned down because of a fault in the oven that was not disclosed, by seller, at time of purchase" [We keep files on ever aspect of the house -- repairs, alterations, enhancements, etc. This documents what was done, when, by whom and for how much (the latter allows adjustments to resale value). So, in addition to acting as a convenient reference for us, it also forms the basis for any future "disclosure" requirement. It gives the impression of thoroughness. Contrast with "No, I can't think of anything important..."]

Note that disclosure applies to anything you *learn* about your property up to the time of sale. So, if a home inspector discovers something, you have to report that, as well ("Gee, I didn't know the house had termites until the inspection, yesterday!")

Of course, if you don't know something, you can't disclose it (e.g., the house sitting on a toxic waste site)

Agents (and inspectors) have additional requirements consequential to their licensing.

And, commercial properties have some additional "seller bias" built in (the thinking being that a buyer of a commercial property can/should have the resources to conduct a detailed inspection).

Of course, you can *lie* about what you know. But, you'd have to be wary of being caught in that lie (and thus guilty of intentional fraud instead of negligent fraud). Remember, the party suing will have "representation" and likely have experience in that regard. Esp if an insurer with money at stake!

Looking at date codes of a PCB (or the components ON the PCB) in an appliance and comparing to your term of ownership can easily convince a jury (of people who aren't smart enough to get out of jury duty!) that you *must* have known of a repair -- even if you deny having made it, yourself.

Household wiring, here, is stamped with a date code every few feet. So, you can prove that it was installed no *earlier* than that date (and it was obviously installed no LATER than the date of the legal action!).

Neighbors can be queried to get an impression of the type of person you are (DIY vs. hire-out vs. pay-unlicensed-under-table). Neighbors are often very chatty with folks without realizing where that information might be going! (We've had private detectives come to the door asking about other folks in the neighborhood)

The county clerk has records of permits issued against your property, etc. You usually have to disclose any insurance claims made within the past

5 years.

Point being, if someone incurs a significant loss (including loss of life) as a result of one of your actions, there is likely a significant motivation to go after you for (civil) damages. Esp if the alternative is for that someone (insurance company!) to be faced with those losses!

Of course, that's *here*. Commenting on how things are done *there*, many thousands of miles away with different legal system, etc. would be as foolish as expecting someone from THERE to think they understood how things are done *here*! (How close to the front door of a public building can I be and still legally smoke a cigarette? What are the rules regarding my carrying of a firearm in public? Under what conditions do I have to *pay* for my rescue? What are the criteria that constitute "running" a traffic signal? What are the limits on "automated traffic regulation enforcement"? What constitutes a "barking dog" violation? How much light can be directed skyward from exterior illumination? What color temperature limitations are placed on those fixtures? When is rainwater harvesting *required*? How deep can water accumulate before considered a fine-able action? Over what size area? etc. A myriad of things that the pols and citizenry, here, have decided are important enough to codify into law. It's always amusing to see where a region's values lie!)

Reply to
Don Y

Did you know there's a couple little pieces of plastic at the bottom door hinge in Kenmore fridges that makes the door close the last few inches? It wears out and becomes smooth and the door has a tendency to stay open a bit more than the magnetic seal can grab.

Easily available as a repair item from the parts suppliers, kind of stupid expensive ($20 US or so) but not the sort of thing that's easily 3D printed or otherwise.

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I think ours is 20+ now. Ice maker still works, no issues.

Reply to
Spehro Pefhany

not so. the insurer is not a court of law, they just need a suspicion to not payout and then you have to go to court and fight (and pay) to get your policy enforced and they will fight. your chance of winning is rather small especially since they drew up the contract.

Reply to
David Eather

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