Yesterday, my toaster quit working, so I opened it up to see if I could fix it. Now this toaster is fairly old; I believe I bought it about 1979 for about $10 or so. So it probably doesn’t have any microprocessors or modern electronics.
Well I managed to get it to work again, although I have no idea how. I saw nothing in it that was obviously broken, so other than cleaing off some of the bread crumbs, I didn’t do anything that was likely to fix it.
But my question is, what mechanism do old toasters have for timing? I could see nothing in it that would perform a timing function. There were a couple “black boxes”, that is, small black plastic enclosures that had no obvious way to open. I suppose these might have contained electronics, but based on the purchase date and price, I find that unlikely. Electronics just weren’t that cheap in those days.
So is there any other method use for timing in old toasters? Perhaps some metal that expands from the heat and completes the solenoid circuit that releases the catch?
Also, what causes the tick or click that occurs about halfway through the heating cycle?
bimetallic strip? Guessing - two dissimilar metals with differential expansion rates. It bends when heated, makes/breaks electrical contact, toasty goodness results.
New toasters have an added safety feature that I noted the other day - the unit must be plugged in order for the toaster to be pushed into the “toast” lock-down position.
Most of these cheapie toasters had a clockwork type mechanism, some of which were fairly quiet but most you could definately hear some kind of unwinding sound.
When you depress the lowering mechanism, you charge the timer spring.
When you change the timer, what you are doing is altering the speed at which the mechanism unwinds.
These can get grubby over time and a quick clean out can be a simple fix.
I’ll also add that the more expensive ones of this era had a small cam driven through a small gerabox, which itself was driven by a tiny electric motor.
The cam pushed the catch that held the toaster tray down.
The start position of the cam is what set the time for the toast, just a knob on the side of the toaster that you turned.