Just realized power supplies matter way more than I thought

I used to just grab whatever cheap power supply came with the panel kit for residential jobs, figured it all did the same thing. Then I had three callbacks in two weeks on separate installs where the alarm kept randomly resetting during voltage dips from the fridge compressor kicking on. Anyone else had cheap PSUs cause phantom issues that you spent hours tracking down?

3 comments

3 Comments

the_wendy8d ago

So were those cheap PSUs actually putting out clean DC or were they just barely filtering ripple? Like did you ever scope them to see what the noise looked like under load?

marywilson7d ago

Buddy of mine tested one of those no-name units years ago. Hooked it up to a scope and said the ripple looked like a bad EKG reading. The 12V rail was basically just AC with a hat on.

jana_jones6d ago

Did your buddy ever check if the ripple got noticeably worse under load, like when the PSU was near its rated wattage? I've seen some of those cheap units start out halfway decent but then the ripple noise triples once you push them past 60-70 percent load. It's usually the circuit design that falls apart first when things heat up, not just the capacitors.