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Originally Posted by RetroHacker
...it's a pain working around a way to safely direct-couple video into a stage in a hot chassis television set... -Ian
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Ian, the way I always coupled anything into a TV set (or any kind of electronic equipment), whether or not it had a hot chassis, is to use a blocking capacitor in series with the circuit or instrument I was connecting to the set. Over thirty years ago, I learned a lesson I'll never forget when I tried to connect an oscilloscope to a color TV with a transformer-powered chassis, to monitor the video signal. I went across the contrast control, without using a high-voltage blocking capacitor in series with the lead to my scope's vertical input. Turned everything on and--whoops!--I heard a loud noise coming from inside the oscilloscope. By the time I heard that noise it was too late--the voltage across the contrast control in my TV had arced through the intensity control of the scope. Didn't really ruin anything (the scope still worked amazingly well for several years afterwards), although from that moment on, whenever I'd adjust the intensity control and the movable arm inside the pot contacted the burned area of the carbon resistance element, I would hear a noise very much like a rifle shot.
To this day I am amazed the scope didn't blow a fuse, or the power supply was not heavily damaged, the first time that happened. Hmmm.
