Tinkering with Electronics

I was sent a Pentair Intellitouch Indoor Control panel from a gentleman who said the controller showed nothing on the display, made all kinds of noise, and got so hot that it browned the white plastic base.  He was worried it was going to catch fire! When I received the unit the first thing I did was a visual inspection.  Nothing was immediately obvious so I connected it to my bench power supply and turned it on... upon power-up it beeped, screeched, and the on-board 5 volt regulator (U8 in the bottom right) got very hot.  The preset 1/2 amp current limit kicked in almost immediately, making the voltage drop under 5 vdc so the board couldn't control the piezo speaker (hence all the beeping and screeching). These units typically draw around 140-180mA (depending on your led/lcd brighness settings), but this one instantly cruised past the 500mA limit.  The over-current condition was a clear indication that there was a short somewhere.  A more thorough inspecti...

One question I get asked a lot is "how do you power a controller on your workbench?" It's so simple I almost hesitate writing about it, except that folks might not try it for fear of damaging their crazy expensive system... We're all used to seeing the 12(or 10)/18/24 volt AC system transformers in our outdoor panels, but when I first started tinkering with Pentair stuff, an Intellitouch "laptop trainer system" found it's way into my possession... It's a full-fledged Intellitouch, but has different firmware and no means to power the relays and valves. And it was powered by a single 12 volt DC wall wart.  Huh??  The system transformer puts out AC volts, not DC volts! This 12 volt DC wall wart was glued onto the trainer system I noticed that the 12 and 18 volt AC inputs are converted on-board to DC (while the 24 volt AC input is left alone).  The 18vac converts to about 24vdc and powers all of the relays, while the 24vac powers the va...

Welcome to my humble electronics blog, where I'll mainly be posting articles related to various test equipment I've obtained and pool automation equipment that I like to play around with.