Fridge repairRemoved that dodgy looking 47K resistor from the thermostat's butt. As soon as I grabbed it, all the paint came right off of it !
Poor resistor was not cracked/damaged at all... the cracks were in fact just the paint peeling off ! I get the thermal cycles got the pain to crack, but it was just the paint cracking.. the resistor itself is 100% fine and measures spot on...
So the problem is indeed the thermostat itself. Old man found a replacement in his stock at home. A generic kit that will need minor mods but should work just fine. He is packing it right now and will be shipping it first thing tomorrow
In the meantime I have to cycle the fridge/copressor on and off by hand to keep my food fresh..... old man says ratio is about a third to a fourth. So total run time per day / 24H must be 6 to 8H, something like that. So ideally turn it on 15 minutes then turn it off for 30 to 45 minutes. but that's too much work for me... I am no slave. So I guess it will be more like 1hour on and 2 or 3 hours off....
Then while I am sleeping, 8 hours... either leave it off but temperature might drop too much I don't know... so might leave it on all night...
Ideally old man told me to just power the fridge via a timer but I don't have one. Probably costs 2 Euros on Amazon but I need a solution right now, not in 3 days (dream on) or a week, all being well with shipping of course, you have to have faith.
Or maybe I could cobble an electronic timer together quick and dirty in the lab ?! That could be a fun project..
I have relays and TRIACs as well. I could just make a little timer running from a battery, for convenience/quick design, and just make it drive a relay ?!
So I need a 555 I guess !!
Do I even have one ? No idea as I have not yet got to the point of sorting IC's yet. I am still sorting discrete semi-conductors at the moment.
Worst case I guess I could just use some op-amp and make a variable duty cycle square wave oscillator ?
Of course doing very long periods is not very convenient / reliable with RC networks.... so maybe I could instead make such an oscillator run at a faster / more convenient speed, using "manageable" values of C and R, and then feed that a logic chip, a counter/frequency divider, maybe 2 of them cascaded, so I could achieve long periods yet easy to adjust ? Then the output of the counter would drive a little transistor which would drive the relay that would turn the mains on and off for the fridge.... hmm yeah that sounds like fun, let's try to cobble that together this evening !!!
My first design project in my new lab, first project in 15 years !!!
All thanks to my fridge failing ! Everyone should have a failing fridge in his life, it brings good !!!