1958 home GA. Modern panel (1990’s?). The home had a mixture of 2 prong ungrounded receptacles, 3 prong ungrounded receptacles and three prong grounded receptacles. The home had a handful of visible electrical deficiencies (DIY type crap etc.) Panel cover was obstructed and I was unable to remove it. Also, there was no visible ground to be found. No ufer. No ground rods.
One thing I have never seen. I plugged in the 3 light tester and of the yellow lights would brighten then dim. Interestingly, the pulsing was rhythmic. One second bright, one second dim.
Any ideas what would cause this and is it an indicator of something more complex?