Pete's Videos Aye up Guys new tester from across the pond

[Pete999]

And you can make it yourself

 

[Lucien Nunes]

Hang on a mo. The cap and 510R resistor in series make an impedance of 5.3k at 60Hz, so at 120V they will act like a near constant current source of 23mA. What if the sounder doesn't use 23mA? Then the voltage across it will be completely wrong and it might either not work, or go bang, or whatever. OK, it works with his particular sounder, but there should be a zener diode across the output of the rectifier, or two of its diodes should be zeners, to limit the DC voltage if someone uses a different one. I won't comment on anything else.