Grow your own crystal cartridges?

[cmjones01]

I was idly browsing the upcoming BVWS auction catalogue and saw a Philips record player. It occurred to me that it would probably need a new cartridge made from finest unobtanium. My train of thought continued: so if these things have a Rochelle salt crystal inside, what about replacing that crystal? Where does Rochelle salt come from?

A little Googling revealed that you can make it at home, from common kitchen ingredients (baking soda and cream of tartar). And a home-grown one can be used to demonstrate piezoelectricity. Here's the link I found:

http://rimstar.org/materials/piezo/h...ic_crystal.htm

The hard part is probably shaping the crystal and attaching wires to it somehow, but surely it's got to be worth a try, especially as supplies of ceramic cartridges start to dry up.

What do you think? Is it a mad idea?

Chris

Same stuff as in crystal earpieces, loads on the web.

[Radio Wrangler]

Depositing metal electrodes might be difficult.

I assume that a crystal could be mounted in sealing wax on a stick and then ground using a diamond wheel and a microscope a bit like diamond cutting but a lot cruder.

On the other hand, are there any consumery things that could be bought cheaply with piezo ceramic lumps in them which could be cut down in a similar way... or is lead-zirconium titanate available in handy strips?

I don't think it's impossible.

David

[Ed_Dinning]

Hi Gents have a look at Bi-morph strips, usually in a PZT material.

Ed

[emeritus]

I know from when I was involved in IC fabrication that some crystals, such as the Silicon crystals from which IC wafers are cut, are anisotropic, meaning that a crystal has to be grown and/or cut on a preferred axis in order to obtain the desired electrical characteristics. I don't know if this applies to the type of crystals used in cartridges.

[MotorBikeLes]

Anything with any properties which are directionally dependant are by definition anisotropic.
First get your suitable ceramic or other medium. Then silver it. This was always done by firing on to the ceramic surface, but why not simply use a combination of light pressure and electrical silver paint?
Suitable crystals? Any thing piezo must surely do, but its output may be of wrong order.
What about the material used in the "ten a penny" gas lighters sold for BBQs etc? I have a few old ones here out of gas fires, but never stripped one down.
I have some non-working ultrasonic tanks (mentioned in another thread here a while ago, but still waiting for a pal's help). I image a chip off one of the transducer blocks and the aforementioned silver paint could be tried. If this stuff is really becoming unobtainium, it won't be long before you see me with a diamond wheel cutting one up and doling it out in small packages for suitable remuneration (lol).
Les.

[G6Tanuki]

I'm wondering if the thin circular piezo sounders used as the beeper in things like microwave-ovens and digital alarm-clocks might be cut-downable? They've usually got one side bonded to a brass backing, the other face is silvered to take a soldered-on connection.

Ultrasonic transducers might also yield a suitable source.

[cmjones01]

There are lots of good ideas here, which I'm pleased to see. I've never looked inside a crystal or ceramic cartridge to see how they're made. I wonder if there's anything tricky about how the stylus is connected to the piezo element. If not, then a sliver of piezo sounder would be a very neat solution.

Chris

[AC/HL]

Strain gauge elements have been suggested in the past.

[Herald1360]

Electrets?

[Synchrodyne]

Originally Posted by cmjones01

There are lots of good ideas here, which I'm pleased to see. I've never looked inside a crystal or ceramic cartridge to see how they're made. I wonder if there's anything tricky about how the stylus is connected to the piezo element. If not, then a sliver of piezo sounder would be a very neat solution.

The attachment to the initial post in this thread - https://www.vintage-radio.net/forum/...ad.php?t=64264 - provides some background on the mechanical and other aspects of piezo catridge design.

Cheers,

[Mike. Watterson]

I've cut piezo sounders with a dremmel. I shall solder a cut off brass part from a lamp socket to hold the bamboo or steel needle. I'm 100% sure it works as I've used them as "crystal" microphones. The old 1960s crystal earpiece was like a record player cartridge crystal or ceramic stick glued to aluminium foil. The current ones in Maplin that look identical are actually a just a piezo disk. So I made and earphone case like old moving iron disc earphones (the 2K and later 600 Ohm telephone type) and found that cheap piezo disk with about 4.7K across it works well instead of 4K phones on 1929 radio and nearly as good as in ear 32 Ohm buds on a phone/MP3 player/Laptop!

My 1935 HMV is actually moving iron magnetic pickup, it works with bamboo or steel needle.

[Hartley118]

I've successfully repaired a rather rare early 1950s EMI 'type C' 78/33 turnover ceramic cartridge by soldering directly on to the metallised ends of the ceramic element.

The element was originally clamped to foil conductors which had disintegrated. After trying and failing to replicate those, in desperation I tried direct soldering (quickly!). It worked a treat, with no detectable damage to the piezo properties of the ceramic.

Martin

[MotorBikeLes]

Just one suggestion. If you are going to solder to silvered ceramics, take note of TEK's advice regarding their old 500 series with silvered ceramic "tagstrips", and that is to use solder with about 3% silver. They even fitted a small coil inside every 'scope. I still have a couple, used a few months ago on big ceramic piezo blocks in an U/S cleaner.
They still turn up on Ebay, or it can be bought (expensive) from such as RS components.
Les.

[Hartley118]

Originally Posted by MotorBikeLes

Just one suggestion. If you are going to solder to silvered ceramics, take note of TEK's advice regarding their old 500 series with silvered ceramic "tagstrips", and that is to use solder with about 3% silver. ...

Thanks - a helpful reminder for soldering silvered ceramics. I seem to remember though that the metallizing on the 'Double C' piezo ceramic element was a copper colour, so I used ordinary tin/lead solder. How the metallizing was done I'm not sure - presumably starting with a chemical treatment, but I'm sure that EMI Research had a few experts in the subject back in 1950.

Martin