[Coco] Re: [Color Computer] Ouch!

[Rogelio Perea]

"Neil Morrison" wrote:

> My all time favorite was told to me by a fellow electrician who...

Ok, a little off CoCo topic but here it goes:

Back in the mid 90s a close friend of mine and myself were working at a combo AM & FM transmitter site. Standard procedure dictates that the operator must set to ground all potentially hazardous contact points within the transmitter using grounding rods located in the equipment. Power must be removed completely before attempting any "open cabinet" surgery in the transmitters so he followed the safety procedures and proceeded to work in the Harris FM transmitter. Meanwhile I went back to the other half of the room to start working on the AM transmitter; as I leaned over to open my toolbox a bright flash illuminated the whole room and a loud POP! noise went along... then the smell of burned out metal... as I turned around there he was, my friend holding what was left of the grounding rod metal (the metal part, the handle was a large solid plastic piece) all dazzled and confused, he just kept saying "I can't see I can't see". His sight returned soon enough, he was just disoriented as when someone flashes a camera at a very close range.

The problem was caused when he touched one of the contact points of the filament voltage control rheostat, the control breakers should have disconnected if from the 240 VAC line but a design oversight prevented that, all the pilot lights were off in the mains AC controller so my friend had relied on just disconnecting all the breakers built in the equipment, not the mains on the wall switch... everything was out of power except that wire in the filament circuit.

We did go back to Harris and prompted them on the issue. The HT10FM transmitter was brand new in their product line and had some design quirks, oddly in that region of the filament circuit - the rheostat overheated under normal operation to the extent that the resistive elements eroded badly causing a big dent on the control that prevented the wiper from moving... that's another story.

The moral was that we learned (luckily with no more harm than that temporary flash-dazzle) that ALL power must be removed not matter how redundant the procedure might look.

Moving this into the CoCo topic, later that day I was at home and designed a full length graphic (letter sized) using CoCo MAX 3. I used the basic idea of those old TV ads about drugs -> "this is your brain, this is drugs..." putting some notes besides the drawings fashioned like:

"This is a grounding rod"
"And this is a rheostat contact point"...

the sign stood in the transmitter side entrance for a long time. Outsiders took a while to grasp the concept :-)


-=[ Rogelio ]=-
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