I got given a tester as a gift, and then once a week I focus my digital camera on my transponders and watch if they light up.
In the beginning, I thought it was only the reflection of the tester lighting up because although the jammer was still screaming inside, as soon as the tester was switched off the leds went off. The warning screams for five seconds, but the leds light up as long/short as there is an infra red source triggering it. Noticed this on the Blinder m25 extreme, Laser tec pro 20 and the Zr3 and 4.
Thanks for the concerns, but I believed the jammer would be fried and I would have to buy a new one anyway, so I decieded to use it until it fails to see just how robust it is.