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Old 14th Sep 2018, 12:37 pm   #1
David Simpson
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Default GECoPHONE Crystal Set No1

Just been given this old 1922 gem for repair, from a close friend. Its in my R-R 3rd Edition on page 39. Would it have been GEC's first venture into crystal sets ? Its an "open detector" version, with a spare galena crystal mounted in the lid, and a set of 3 ebonite connectors.
Haven't delved inside, but it needs a jolly good clean, and there is a bit of damage to the lid & r/h hinge. But otherwise in jolly good condition for its age. Temp rigged it to my 80m doublet & E, & plugged in a pair of Brown's, but no reception. I do have some GEC loading coils somewhere, for a 1927 TRF, but another box of coils are mainly Revophone ones.
Any advice most appreciated, please.

Regards, David
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Old 14th Sep 2018, 12:46 pm   #2
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Default Re: GECoPHONE Crystal Set No1

You might want to temporarily but a OA81 or someting similar in place of the detector its possibly gone HR and needs a new part of the crystal exposed.

If it doesnt work then look deeper.

Cheers

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Old 14th Sep 2018, 1:14 pm   #3
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Default Re: GECoPHONE Crystal Set No1

You only need the extra loading coil for long wave, for medium wave it should work as is with link fitted.

The headphone sockets appear to have the broken remains of previous plugs still inside!

The set is designed so that a single headphone is plugged vertically into the left most pair. Two headphones are plugged in horizontally and are thus wired in series.
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Old 14th Sep 2018, 1:14 pm   #4
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Default Re: GECoPHONE Crystal Set No1

I have a similar model which performs well on MW without the need for a loading coil.

IT NEEDS A GOOD EARTH CONNECTION to provide capacitance to the aerial wire.

More info here:-

http://earlywireless.com/gecophone_no1_picinfo.htm
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Old 14th Sep 2018, 3:24 pm   #5
David Simpson
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Default Re: GECoPHONE Crystal Set No1

Many thanks Graham for the link.
Right enough guys, an OA81 is a handy galena substitute. I'll give the crystal's surface, and the spare's, a gentle clean with a wee st. steel brush. Likewise the whisker. Thankfully there is nothing stuck inside the sockets,'cept that one has some white oxide deposit around the inside. The info card in the lid describes the orientation for headphone fitment. I've a heffin good earth connection to an outside sub-soil matrix of rods & buried bare copper wires - which I need for my old ex maritime AM Tx to work 80m. Everything getting a good clean is priority now, then fixing the wee split in the lid's corner.
The GECoPHONE is sat on the bench next to my u/s Hameg 203/5(still not repaired). But then late 20th century TTL circuitry, falls into insignificance compared to a lovely original crystal set. Me knowing almost SFA about TTL etc. doesn't help.

Regards, David
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Old 14th Sep 2018, 4:39 pm   #6
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Default Re: GECoPHONE Crystal Set No1

Hi David,
There's not much to go wrong with these. Certainly worth trying a Germanium diode as has already been suggested. Mine did have an intermittent on one of the variometer connections - just need cleaning ISTR. As the LW loading coils are like hens' teeth you might want to try the trick that I used (see http://www.tibblestone.com/oldradios/Gecophone.htm ).
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Old 14th Sep 2018, 5:26 pm   #7
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Default Re: GECoPHONE Crystal Set No1

Once again - thanks to Graham for his link, and now thanks to Keith for his tibblestone link.
Circuitry now removed & everything looks un-touched. The lovely variometer, and the hand-built capacitors are a revelation.
In the past, I've already restored a Revophone & an Ediswan crystal sets from that era, plus a Tottenham spark-gap wavemeter. So here we go again.
I've a box of old loading coils, but their plug arrangements are different. So will have to follow Keith's example regarding a LW coil adaption.
What an exiting vintage radio world we live in. At the beginning of the week I was banging-on about old BBC valve testers, and a modified Mullard HSVT. Now - a wee gem of a crystal set is dropped into my lap. Back to basics, great.
Gentle wiping with a piece of kitchen roll & meths has already removed some evil looking crud from the top of the lid, and all the mahogany will hopefully polish up a dream. Yep - I've been quick & careful(as the actress said to the Bishop) regarding using meths - to avoid lifting the original varnish. Usual scratches here & there, but nothing serious considering the set is 96 years old.

Regards, David
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Old 15th Sep 2018, 11:01 am   #8
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Default Re: GECoPHONE Crystal Set No1

Just a note to warn others that meths dissolves french polish and you can end up in a real sticky mess if you are not careful.
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Old 20th Sep 2018, 5:12 pm   #9
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Default Re: GECoPHONE Crystal Set No1

Once again Guys, thanks for advice. Set now working fine & cleaned up a treat. Like Keith, who didn't like Radio 5 dominating the wavelengths, I was pestered with Radio Scotland, who normally aren't too bad, but today in particular had Nicola Sturgeon banging-on. Thankfully, by means of an adaptor I've built, an additional coil helps in getting Radio 4 on LW. But then I seemed to be getting weak adjacent channel interference from an Arabic sounding channel.

Regards, David
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Old 21st Sep 2018, 9:25 am   #10
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Default Re: GECoPHONE Crystal Set No1

Quote:
Originally Posted by PJL View Post
Just a note to warn others that meths dissolves french polish and you can end up in a real sticky mess if you are not careful.

Been there, done it! I now only use warm water with a splash of washing up liquid. Apply with a cloth, and dry off with another cloth before liquid has time to soak in any joints.


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Old 21st Sep 2018, 11:00 am   #11
David Simpson
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Default Re: GECoPHONE Crystal Set No1

As PJL & John says - be very careful with meths. Just a piece of nice absorbent kitchen paper roll with not too much meths on it. Meths is fine on ebonite, but again be careful around etched lettering, then a dab of MrSheen multi-surface gives a nice polish.
As you'll see from yesterday's picture 2, the woodwork & ebonite haven't suffered from my initial quick wiping with meths, & have polished up jolly well.

Regards, David
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