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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 2nd Jan 2020, 3:54 pm   #1
Pete_kaye
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Default Home made earphones

A few years ago , I made some simple crystal earpieces from old fire alarms . I fitted 47K across each one and they all worked fine . Yesterday I tried them again with crystal set and only one worked. I got readings of v. high resistance with my meter but not a peep .Do these earphones disintegrate with lack of use? Shall I just bin them?
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Old 2nd Jan 2020, 4:09 pm   #2
G6Tanuki
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Default Re: Home made earphones

do you mean you used the type of 'sounder' things that are a flat brass disc with a piezoelectric element bonded to one face?

This sort of thing: https://uk.farnell.com/multicomp/abt...30v/dp/1675548

or the similar ones in a small circular plastic case.
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Old 4th Jan 2020, 12:38 pm   #3
Pete_kaye
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Default Re: Home made earphones

Yes. I did not explain earlier very well that the high resistance readings were only when the 47 K was disconnected.
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Old 4th Jan 2020, 3:58 pm   #4
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Default Re: Home made earphones

It would be high, only ceramic twixt the probes. Ceramic sounders last for ages (as long as clay pots I suppose which is a very long time).
 
Old 5th Jan 2020, 6:26 pm   #5
Biggles
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Default Re: Home made earphones

We scrap quite a few old style (80's ish) phones at work (and yes, they really are well beyond repair!) and I have found that using two earpieces from them connected in series make a usable set of phones with medium impedance for things like crystal sets. They seem quite sensitive too. I always find crystal earpieces sound a bit thin and tinny for my liking.
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Old 8th Jan 2020, 5:07 pm   #6
Pete_kaye
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Default Re: Home made earphones

they've gone in the bin . It is easy to get bogged down in trivia.
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Old 13th Jan 2020, 5:30 pm   #7
daviddeakin
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Default Re: Home made earphones

"earpiece from fire alarm" is the most bafflingly wonderful thing I've heard all day
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