I will generally try to repair something prior to chucking it. My very first project on my Tormach CNC was making a new latch for the electric tea kettle.
I carry this practice to extremes sometimes. The retainer for the rewind spring on my Lufkin tape rule broke so I I reverse engineered the broken part and machined a new one. A bearing on the pulley side of the motor in my B & B belt sander and it didn't appear to be replaceable so I ordered a new sander. Shorty after ordering, I got wondering if maybe the pulley was screwed on with a LH thread. Sure enough, it was. I rummaged through my collection of salvaged bearings and found an exact replacement; sander repaired.
Even of a product isn't repairable, it gets reduced to a pile of parts. Hence the salvaged bearing collection. Larger appliances like printers will provide useful pieces of stock for future projects. When heating appliances fail, it is often a $.50 thermal fuse.
An interesting story regarding thermal fuses; a coffee maker quit and on dissecting it , the thermal fusehad blown. The interesting thing was that there were two thermal fuses wired in series. Very puzzling. As I thought about it though, product acquiring a CE mark require a failure mode analysis. Multiple factors involve the determination of the severity of failure mode including detectability, probability of failure, and risk to person and/or property. Usually, those factors are multiplied together to get a final score which determines if preventative action is required. In the case a failure of the type woouldn't be detectable. Also the risk of serious damage to person or property is n the event of a failure to open is high. Lowering the score by decreasing the probability of a failure remains a desirable option.
There is a finite probability that a thermal fuse would fail to open when it should. If that probability were say 1 in 10,000, the probability of both fuses failing to open would be the product of the two or 1 in 100,000,000. Clever people, those Chinese
OH RJ you just brought up a very troubling time in my career.
I was a product designer for the largest global consumer power tool company that decided to purchase the small appliance division of GE. Back in the 80's drip coffee makers were some what new. They are a very simple device, including a water reservoir, hot water generator, coffee basket with water spreader and receiving carafe.
The hot water generator is co -extruded aluminium with a hollow tube and one that houses a calrod element. Water falls from the reservoir thru a check valve into the hollow tube in the hot water generator, gets heated expands and goes up into the basket.
The electrical is very simple. A normally closed self resetting thermostat is thermally attached to the hot water generator. The thermostat has a temperature setting above the temperature for water being heated. When all the water has passed through the generator the temperature sores up and the thermostat opens. Often the hot water generator top surface serves as the "keeps warm" surface (hot plate) for the carafe. When the temperature falls the thermostat closes briefly and the temperature rises quickly ,and then opens. And the cycle repeats as long as the coffee maker is turned on.
Now at the time we knew that the self resetting thermostat could eventually fail either open or closed. Open is no problem. However closed is a disaster. We knew this and UL / CSA require the product to be safe with a single component failure ..open / short.
So a one shot thermal fuse was installed. The value being above the normal working temperature by a margin to avoid nuisance tripping. Safety test showed that the product to be safe with a single component failure. All was good.
Untill the popularity of drip coffee makers meant we were selling over a million a year...And the occasional report of a kitchen fire caused by a coffee maker. **** how could that be? When we investigated the failures there wasn't much left to help, and we spent hundreds of hours trying to figure out what was happening. My company was extremely safety concious, and no designer wants to be responsible for loss of life. Which we never had fortunately.
Long story short, we did get the manufacturer of the thermal fuse to admit that there was a very small probability of their thermal fuse not opening on temperature exceeding their rating (
AS RJ mentioned).
So our ultimate solution was to insist that all of our coffee makers have two thermal fuses. The criteria being that if the fuses were from the same manufacturer they had to be two different values to make sure a batch problem didn't affect both...OR we could use two different manufacturers with the same value.
Based on our findings we lobbied UL / CSA to require in the standard that two thermal fuses be required for coffee makers. It was an North American initiative, not Chinese. Not that I have anything against Chinese suppliers.
And now to get back to the repair aspect of this thread. We knew when we analysed products that were returned under warranty that there a lots of DIY'ers out there that tried to fix their appliances and we frequently found one shot thermal fuses that were bypassed. So the standard also introduced tamper resistant fasteners to try and hinder the DIYer's.
Sorry for the long reply, but this was a tough time in my design career trying to figure out the root cause.
David