planned obsolescence

[dedndave]

the power "packs" often include transformers
and - they generally have a fuse - probably a UL requirement
sometimes, if the output is briefly overloaded, the fuse will blow
however, i have seen it often caused by a shorted winding in the transformer
if a single winding of a transformer is shorted, it is like shorting out the entire transformer
it's electrically similar to an electric motor that is mechanically "locked up" so it won't rotate
the field of the core is broken down - and it acts like a short circuit in AC terms

the transformers are constructed using fine guage copper wire with enamel coating
when a transformer gets hot, the enamel can be displaced and - bang - a shorted winding

[MichaelW]

In recent times magnet wire insulators are much better than they used to be. For devices that are more than a few years old I think an electrolytic capacitor failure is more likely.

[hutch--]

Long long ago when I still had the eyesight to read the colours on blue 1% resistors I used to play with audio and one of the tricks with a fading power amplifier was to remove the old leaky and slow electrolytic capacitors in the signal circuit and replace them with the same value tantalum capacitors. Suddenly the amplifier became quiet again and the square wave on an oscilloscope looked like a square wave again.

In the era of differential input power amplifiers with split power supplies the only place I use electros was in the power supply where their lack of speed did not matter. a 10000 MF capacitor both sides tended to shut the power supply up in terms of noise with no problems at all.

Sad to say my very nice oscilloscope probably does not work any more, the electros would be too old and if I turned it on they would go BANG. Has the same problem with a German lab motor and cable, it ran for a few minutes then an electro went BANG and it stopped.

[BlueMR2]

It seems that no one can escape from planned obsolescence. Today, most products are disposable. Here's a familiar scenario: your washing machine or television breaks down, so you have to call the manufacturer for a spare part. However, they are informed you that the part is not available anymore, so you have to buy a brand new one rather than sending it for repair. That's known as planned obsolescence. Read it here: Planned Obsolescence.

No joke.  Even stupid simple things like bicycle chains don't last anymore.  I replaced the chain on my old beater bike about 2 years ago because it had stretched enough that it no longer shifted consistently.  This new chain is already rusting!  The old chain was 27 years old, no rust... 

[hutch--]

Our friend has been afforded the opportunity to post spam elsewhere.  :lol:

[Gunther]

 :t

Gunther