Did you believe this?!

[Herald1360]

Originally Posted by Focus Diode

I should've added when told this I was trying to work out what were the black and white aerials WITH a BBC2 were!

Brian

They're the ones on top of the coax to an early dual standard set

They just look like they've shrunk in the rain

[threeseven]

How many have heard the comment "you can't earth there, aluminium doesn't conduct electricity" ??
This has been said to me on quite a few occasions over the years, the only reason for it I can think of is that some people get confused with magnetism and conductivity ?

Also, some people think that you can get a dangerous shock from a car battery !! One friend of mine came around for me to test his car battery and I asked him to hold some meter probes on the terminals while I cranked the engine to which he said "no way, I'll get a shock" !! Even when I held both terminals to demonstrate he wouldn't he still wasn't convinced. He said "your trying to trick me" !! This from an IT professional !!

[Dave Moll]

Originally Posted by threeseven

...aluminium doesn't conduct electricity" ??

That would be a bit of a shame, as one property in which I'm involved has an armoured cable with aluminium conductors running from one building to another.

[ppppenguin]

Originally Posted by threeseven

Also, some people think that you can get a dangerous shock from a car battery

Indeed you can't but try getting a metal watch strap caught between +ve and chassis. Your trip to casualty will be unpleasant. I have not suffered but I knew somebody who did.

[threeseven]

Have seen a long 17/19 mm ring spanner blown in two by virtue of falling across the terminals of large car battery !! Quite spectacular !

[Herald1360]

Think about what might happen to an object hit by a 1 tonne mass after it fell about 200 metres

That's roughly the same amount of energy as is stored in a car battery.

I wonder just how many of those spanners said battery could blow apart?

[chipp1968]

Yes Car Batteries should be treated with caution.. Ok to touch the parts.. but shorts!! Im always careful when working on the vehicle .

[bluepilot]

HCF - I vaguely remember this was part of a proposed alternative instruction set for IBM computers. Others that occur to me were PED (punch and eject disk) and WWR (Write wrong-length record) but there were dozens of them. Anyone who has programmed an IBM old mainframe will understand what they were about.

[ppppenguin]

Originally Posted by ppppenguin

I think you could get close to that on some of the Commodore Pets which had software control over the line scan speed of the integral monitor. Set that very low or to zero and watch the line timebase overheat and die.

Possible evidence on the subject, suggesting that my ill remembered scrap from the early 1980s may have been true:
http://en.wikipedia.org/wiki/Killer_..._Commodore_PET

HCF seems have a fair amount of history:
http://en.wikipedia.org/wiki/Halt_and_Catch_Fire

[bluepilot]

You could set light to the monitor on IBM PCs as well by entering the wrong scan parameters into the video card (a 6845 chip?). In the early days, a lot of people (including my wife) were a bit frightened of these new fangled things and it was common for software instruction manuals to include comforting words to the effect that it didn't matter what mistakes you made in typing, you couldn't break anything. Messing around with the video card was an exception to this rule.

[kalee20]

Originally Posted by Herald1360

Think about what might happen to an object hit by a 1 tonne mass after it fell about 200 metres

That's roughly the same amount of energy as is stored in a car battery.

I didn't believe that - but I've just done the calculation - it's true!!

[brianc]

In the early days of colour at BBC Television Centre, there were a couple of fires in studio observation galleries caused by a certain type of colour monitor line output stage catching fire while free running (flywheel sync!!!). The free running, sometimes overnight, was caused by the monitor not being on the same mains supply as the studio apparatus room.

[ppppenguin]

Originally Posted by kalee20

I didn't believe that - but I've just done the calculation - it's true!!

For the record here are some specimen calculations.

For the falling mass:
Potential energy = 1000kg * g * 200m = 2MJ approx (g taken as 10, is really about 9.8)

For the battery:
Stored energy = 40Ah * 12V * 3600s = 1.7MJ

TBH, I don't even want the battery dropped on my foot, even from a couple of metres.

Originally Posted by bluepilot

In the early days, a lot of people (including my wife) were a bit frightened of these new fangled things and it was common for software instruction manuals to include comforting words to the effect that it didn't matter what mistakes you made in typing, you couldn't break anything.

I have written machine control software, here a mistake can bend metal, yes I've done it!

[ppppenguin]

Originally Posted by merlinmaxwell

I have written machine control software, here a mistake can bend metal, yes I've done it!

One hopes that the low level software that controls the drives for large motors doesn't foul up. The thought of the odd 1000hp of motor going gaga doesn't appeal. But I'm sure the power semiconductors will protect the fuses

[Lucien Nunes]

"After cooking food in a microwave oven, you have to let it stand while the residual microwaves escape from it."

"Nicad batteries have a built-in memory to remember how much charge you have used. If you don't completely discharge them, the memory tells the battery not to charge so much next time."

"When we went to France, the house we were staying in had these amazing fuses. If the fuse blows, you simply flip a small lever on the front and it automatically threads a new fuse wire in. There must be a little reel of it inside."

"When installing TV aerial sockets in a number of rooms, if you wire the coax like a ring main all the way back to the aerial, you can connect more TVs without using an amplifier." (The only installation I've seen where the multipath occurred after the aerial. Pictures looked passable but teletext didn't work at all.)

"Valve radios were very unreliable, every week or two you had to take the valves to the shop, have them tested and exchange any that had worn out."

"Hunts Capacitors, manufactured in modern factories in England, have a world-wide reputation for reliability and good service." (From the 1955 catalogue, at which date it might have been true. The statement on page thirteen about Moldseals being '...unique in their rugged construction and completely reliable' sounds a little optimistic.)

Lucien

[vinrads]

I remember my old boss collapsing the field scan on a 405 line t/v then rotating a mirror in front of the screen ,and as if by magic the the reflected image was nearly full screen , how cool was that.

[G8HQP Dave]

CD - "perfect sound forever" (provided the metallisation stays intact, and the record producer does not use too much compression)

DAB - "crystal clear digital sound" (at 256kbps and above)

[paulsherwin]

Originally Posted by Lucien Nunes

"After cooking food in a microwave oven, you have to let it stand while the residual microwaves escape from it."

There are an amazing number of myths surrounding microwave oven use. A good friend of mine (a maths graduate) refused to use a microwave for many years because he was convinced the microwave energy would make the food carcinogenic.

[chipp1968]

I remember being told not to look in the window of a microwave while it was running ...