Belter from HT

[Biggles]

We had the phantom engineer who would unpick one end of a jumper from the D side Krone 237A strips leaving the jumper dangling merrily from the E side still with 50 volts on it just ready to nip the back of your wet hand while rootling around inside the cabinet. Laziness or what?
I used to remove them on sight. Never found out who it was, I think he left the job before I started. We still have some old solder tag connection blocks in one or two of the ancient cast cabinets here and there and lead cables too.
Alan.

[ColinTheAmpMan1]

I had a bit of a surprise a day or two ago, when I unplugged my GW Instek signal generator from the mains socket and allowed my fingers to contact one or more of the plug pins when the plug was fully out of the socket. I felt a very definite tingle! I can only assume, since the mains lead was still connected to the (switched-off) signal generator, that this was coming from the mains filter capacitors. Should this be possible, or is there another explanation?
Colin.

[paulsherwin]

It can happen, especially if the manufacturer has been generous with the X2 value. Sometimes you can even produce a small spark.

[Hartley118]

In our acoustical measurement lab in the 1960s, we used many Bruel & Kjaer top-of-the-range mains operated audio instruments such as microphone amplifiers, octave-band filters, narrow band filters etc. Each piece of kit had two internal mains filter capacitors connected from live and neutral to chassis.

In order to avoid earth loops, only one of the instruments in each rig would be connected to mains earth, the grounding of the rest of the units being via the screens of the signal connections. As a result, plugging and unplugging signal connectors had to be done with care, preferably with one hand in the pocket, because those filter capacitors passed enough current to give a significant belt if the operator bridged the ground connection first - and those big B&K coax connectors ensured a good connection to the hand!

I'm still not sure how we could have complied with today's safety earthing standards and yet avoided earth loops in the measurement system.

Martin

[Top Cap]

In our TV workshop we were warned about a Philips set with a swivel out chassis. Evidently an engineer removed the swivels from the wrong side (2 screws on each) instead of the proper identical looking hinge (1 screw) on the other side. The whole chassis fell into his hands and took his life. Myself, well the worst belt was aboard ship working on a radar set. I used a crocodile clip to connect to a 1v video output but I was in for an unexpected surprise. If you can imagine holding a large White card in your left hand, then slap your chest hard (I mean really hard!) with your right hand then staring into the White card. That was what the journey to the next world was like but fortunately, the ship rolled being in rough seas and I broke contact. Of course my other hand had been holding onto the steel bulkhead to steady myself before I made contact, the next thing I knew was, I was lying on the deck. Lucky for me the ticker did not stop. Cause of the shock? A dead short 1kV capacitor passing negative 850V to the video socket. An experience that I will never quite forget.