I bought 4-in-1 AC meter, PN 200123 earlier this year on Amazon, and it worked pretty well. However few months ago I noticed that after 0,5-1h of use the lower-left corner of the LCD display was going completely dark, which then progressed to cover the whole display – after about 3-4h. The equipment is used only occasionally and after rest the display would start fully legible, so it’s obviously not the logic problem. To be clear, the “Power IN” cables are 10ga (6 square mm), fed from 40A SSR.

Today I got equipment ready for another run, but had to shut down immediately, as there was NO display, just the smoke coming from behind the panel. Motor didn’t even “click” on. After taking the panel off and checking connections, I tried again – same effect, this time I saw that the smoke was coming from the CT ports, which are near the problematic corner. I ordered a replacement unit, disconnected the existing one and now everything works.

I initially thought the display was overheating, so I put a forced-air conduit on it, but now it seems overheating was not caused externally but inside the meter itself. I obviously want to avoid repeating the same problem, so here is the question – what could have caused this problem?