A common problem on old phonographs with crystal cartridges seems to be that the Rochelle salts crystal disintegrates with humidity. I'm working on one of these phonos now. I have an idea how it might be repaired, but rather than reinvent the wheel, I thought I would ask how others have attacked this problem.
It seems to me that I might be able to use a ceramic piezo element like this one
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to replace the old crystal inside the phono cartridge. The size is just about right. Has anyone tried this? If so, is the output level and frequency response comparable to the original crystal?
Or is there a better approach (that doesn't cost more than an old phonograph is worth)?
I haven't a clue, but you should probably ask in rec.antiques.radio+phono Because there would be people there trying to keep (and revive) older equipment, and this is the sort of thing that gets discussed over there (even if I'm not sure this specifically has been discussed).
It must be a pretty big cartridge if it will take a 15mm diameter ceramic disc. In my experience, the crystal/ceramic element in a phono is quite small so I think you are not going to have any success in repairing it. The elastic suspension carrier for the element might have deteriorated as well so you will probably find this a problem.
Not to put too fine a point on it, why not just buy a new ceramic cartridge and save all the hassle? Though looking at some of the prices here
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you might not like it.
You can get better prices here but the range is smaller
Well, what is the worst that could happen if you spent a coupla bucks on a ceramic element and it didn't work as well ?
I suspect that the next step would be to find the cost of a compatible replacement cartridge and decide if it is worth the extra money.....
Probly not..... Sometimes you have to spend a few bucks just to find stuff out...
I would, personally, never consider repairing the inside of a phono cartridge. It's too tiny. Throw some bucks at the problem. That's the American way :>))))) !!!
Actually, I've already examined the failed cartridge. The old crystal seems to be a slab about 15mm long and 10mm wide, fitting into a space 15mm wide and 25mm long inside the cartridge shell. I thought I might be able to grind the sides of that circular 15mm barrium titanate piezo on a belt sander to adjust the fit. Or if it shatters on grinding, find a slightly smaller one.
My old crystal was clamped into the cartridge by two rubber blocks, one glued to the top shell and the other to the bottom. The gap between measures about the same as the crystal thickness. Are these what you mean by the elastic suspension carrier? There was also a thin, crumbly black coating on the white crumbly crystal. I took this black coating for a conductive electrode, but if this is an elastic suspension, then I might need to understand its function better. Maybe the barrium titanite can go without a coating. Or I could dip it in the kind of liquid rubber they sell for coating tool handles. This point bears some more consideration.
As for buying a new cartridge, well . . . You guessed right about my willingness to invest cash in the project. This phono isn't a fine antique, and would probably not fetch more that $25 after I finish the repairs. But more importantly, I wouldn't learn anything or have any fun by hiring a specialist to do the job for me. And we're all in this for the fun of it, aren't we?
Thanks for the comments, Andy. Actually, the cartridge in this 1952 phono I'm working on is luxuriously spacious. Overall, the cartridge is about 2" long and 3/4" wide. I only had to drill out four rivets to open the shell. The space for the crystal is over 1/2" wide and fully 1" long. This was obviously made before the word "miniaturization" took root in the electronics industry.
And I follow your logic completely. It will cost me a big 75c to try this piezo see how it works. Compare that to $50 for a rebuilt cartridge, and you can probably guess which I will try first.
But it never hurts to see what experiences others have had first. No point in learning the same lessons over again.
Looking through my junk box I have a couple of old mono phonograph shells ! Like yours the elements have long gone !
However both have a pair of screws, maybe 6ba thread and set 11/16th inch apart that holds in the cartridge. On one these the screws are tapped into the metal of the shell. On the other there is a Bakelite pad, about 3/16th thick with two holes in it for the cartridge and a tapped centre one that goes right through, with a matching hole in the top of the shell.
Maybe you could do something along these lines with yours and fit a cheap Xtal cartridge insert ?
You are better off going to antiqueradios.com forums for advice . I have tried to rebuild cartridges with poor results . It seems things get critical for good sound . Its better to take the element from another modern cartridge .
I can well understand your desire to achieve satisfaction from fixing something for little or no cost, and I certainly wouldn't try to stop anyone from "having a go".
The last time I opened up a crystal phono cartridge was back in the
50's so I don't remember all the details. I am fairly sure the Goldring cartridge I pulled apart didn't have a slab as big as in your unit. I do remember that the crystal was very easily damaged. The crystal element was superseded by a ceramic element in the 60's and these were much more robust.
You might be lucky enough - with great care - to whittle down one of the elements you are looking at as a replacement and then succeed in mounting it along with its soldered connections so that it produces an output. However, I don't think you would be pleased with the sound it produced if any. Give it ago and see what happens. You can only try and if it doesn't succeed then it hasn't cost anything except a lot of labour, and that can be considered free in your case I suspect.
I once tried a similar resurrection project with a 1930's model telephone right down to rewinding the induction coil since I couldn't find a suitable replacement. While it did work to some extent it was a failure in my estimation. In your case however, you are still able to get new replacement parts for your project, so if I were you and I really wanted to get it working as near to original as possible, I would tend to opt for a new cartridge. That way you would get the desired result and satisfaction at the same time.
1950s xtal carts sound grim and damage vinyl records, and for that reason I would seriously consider replacing either the cart or its innards.
Modern 1980s xtals are better but still poor. Modern ceramics are way better. There are 3 types of ceramics, high output, medium output and low output. If you use a ceramic as a replacement you'll need a high output one. A medium or low output one wont give the high output levels of a crystal.
Another option, which may spark disagreement, is a modern medium or low output ceramic plus a fet preamp. The plus side is best sound quality and no significant record wear.
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