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Old 26th Sep 2018, 9:56 pm   #39
1100 man
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Join Date: Apr 2016
Location: Ventnor, Isle of Wight, & Great Dunmow, Essex, UK.
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Default Re: Transformer safety?

Quote:
Originally Posted by kalee20 View Post

There is one aspect which hasn't been considered with respect to safety - and that's failure! Transformers often fail with a shorted turn or turns, getting hot, smoking, catching fire even if wax impregnated (which they often are), without drawing enough current to blow a fuse.

Dropper resistors, on the other hand, when they get old, just go open so they are fail-safe.

If you want to leave a radio running unattended, make sure it's an AC/DC one!
Having played with TV's since I was a kid, live chassis is, to me, the normal state if affairs. There are very few TV's with mains transformers.

Some years ago, a friend, who is very conversant with old tech, had left a 1950's woody radio on downstairs in the kitchen. He had been using it for some years and it had never given any problems. He had been upstairs for several hours when he became aware of a strange smell. Going to the top of the stairs, he could see a wall of smoke. Taking a deep breath, he plunged down in to the kitchen, to find the radio pouring acrid smoke!

The mains transformer had developed shorted turns and overheated. Fuses are usually no use in this case .

So failures do occur with old transformers! I would not leave any old tech, whether it was live chassis or transformer, operating unattended.

I'm not sure how happy I'd be giving any old mains tech to someone who I was not confident was experienced enough to understand the hazards.
We, as repairers, have the responsibility to ensure any items used by other people are as safe as reasonably practical.

A case in point was recently a friend gave me a 1920's art deco heater he had bought."Can you fit a new mains lead"? I declined on the basis that there was minimal guarding to the exposed element and no mains switch. I assessed the shock hazard as being unacceptable. He would have used it without any worries as he, like most untrained people, is not competent to assess the dangers.
All the best
Nick

Last edited by 1100 man; 26th Sep 2018 at 10:14 pm. Reason: more text added
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