It literally took me three evenings to reverse engineer this unit. The circuitry is very complex, but also very well designed. Unlike the previous horrifically dangerous unit I looked at, this one has the outputs isolated from the incoming mains supply. It's still 300V though, so can still give an odd DC zap if you get complacent with it.

The soft start is very simple, but very neat. The regulator chip that limits the current through the LEDs is very impressive in that it can handle a short circuit as standard.

There were two extra features I was unaware of. A low voltage mode for finding polarity of LEDs without risking damage to them, and a higher current mode that steps up from the standard 20mA current to 50mA after about 10 seconds when you are testing higher voltage LED arrays.

There are lots of clever quirks in the circuitry that were quite enjoyable to decipher. Especially the way the main power supply chip is actually an LED driver being used with an opto-isolated feedback hack on its overvoltage protection pin, normally used for detecting an open circuit load.

I did test the other unit, and it too has the 18V feature selected in the same way. But it doesn't have the higher current mode.

To toggle between the 300V and 18V modes you hold the leads together until the display flashes bars.

Very clever design. Both frustrating and a treat to reverse engineer.



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