Home repair for a 1940s low mass crystal cutting head

by **st2580smile** » 23 Sep 2004 14:58

Great to have a completely turntable frendly site to post and ask questions.

I buy/sell/trade vinyl and turntables. It is hard to let any of the tables go.

I have several home record cutters and all the cutting heads are dead. I know that West-Tech http://www.west-techservices.com/index.htm will completly re-furbish to original specs these dinosaurs but I love to save a buck.

Anybody have advise?
Thanks,
PETE

by **cgb** » 26 Sep 2004 00:52

Hi,

these home-recording cutterheads are rather simple devices IMHO. They don't have feedback coils as the more modern, pro units.
The most common damage to cutter-heads happens to the coils. To wind / rewind these one should consult an expert in this field.
There's a guy who is doing cutting and on his site there's a page where he illustrates how he rewound a head. The url is http://www.aardvarkmastering.com/ . Maybe he can give you a hint.

Best,

cgb

by **st2580smile** » 26 Sep 2004 02:29

These units used Rockshell Crystal (pre Piezo) elements. In other words no voice coils. ASTATIC used to have replacements but is out of business. WEST-Tech will refurbish this completely but I would like information to see if I can repair it.
PETE

by **cgb** » 26 Sep 2004 03:02

Maybe I should have read the headline more thouroughly...

All of those home-recorders used Piezo ? I've got no clue about them Piezo things...
I only once saw on an AES historic section demo of a Telefunken home-recorder from the 30s. We spoke into the funnel, and the guy played it back through some small speakers from the same era. Sounded astonishlingly good! Guess that must have been a Piezo too, now that you told me...

Best,

cgb

by **st2580smile** » 26 Sep 2004 06:03

Rockshell Crystal (pre Piezo) elements. Piezo is crystal used in sonar invented by Motorola.
Most less expensive record players used Piezo elements elimitating the step up pre amp for magnetic cartridges.
I just need information about Rockshell Crystal cartridges. Can they be re-furbished without replacing the crystal?
PETE

by **nat** » 27 Sep 2004 16:45

Don't have any specific advice, but you might have more luck looking up Rochelle Salts. I think you may have misunderstood the name -- they are named after a french scientist of that name I believe. There is quite a lot of information about them out there, including on their structure, but I don't know of any info on how to make or repair them.
I'd be interested in what you find -- I think it would be great if someone would reintroduce the MicroAcoustics cartridge designs, which used piezo elements, but in a refined way.

by **st2580smile** » 27 Sep 2004 18:31

Nat your idea is the same as mine. I tried taking apart a stereo Piezo cartridge and applying it as the element in place of the Rochelle Salt but the input to the element was too high and melted the element. I did cut one record this way it was low in volume but was clear!
I tried using a Piezo element from a Radio Shack buzzer that has a copper backing problem with it is the solder connection to the foil top pops off due to the high amounts of watts to make the stylus move.
I did find a company that sells long strips of Piezo material but they only sell in LARGE quanities. These can be cut to any size or shape and are laminated front and back. It would still be cheaper to have the old heads re-furbished by WEST-TECH ($35.00 each). West-Tech also has all the cutting needles and blank acetates (laquers)
Whew...
I will dig into researching the Rochelle Salt crystals, wish me luck. If it works I'll send you an acetate!
Thanks,
PETE

by **nat** » 30 Sep 2004 14:39

How about using the element from a piezo tweeter -- motorola or others? Must be able to handle large amounts of power, and I think that the crystal responds to lower frequencies, but doesn't change shape enought to produce low frequencies at audible volumes, but of course you don't need such excursion.

by **euclid** » 08 Oct 2004 19:20

I do not know of a source of piezo electric crystals. The ones from pickup probably failed because the power required to drive the cutter head is much greater what they were designed to handle,
If there is an old wax-paper or moulded capacitor between the driver tube and the cutter, replace it with a modern cap. They tend to become leaky and even short out after many decades. I would only leave it in only if I was sure it was OK. A shorted cap may destroy your new crystals

The old piezo crystals that were very popular years ago are hydroscopic. They pick up water from the air. Most of them will fail after many years. Keeping them in a sealed box with a dessicant may extend their life greatly.

Crystal cartridges, microphones, and other devices were very popular from the beginning of electric amplification. Their primary advantage was cost. Crystal cartridges were replaced by ceramic cartridges in the 60s. Their output is less but they still can drive most line inputs without a phono stage. Neither crystal or ceramic cartridges require equalization for use in most cheap record players.

by **st2580smile** » 08 Oct 2004 23:02

Thanks for all imput. I just dis-assembled a Motorola Piezo horn and the element is very different than the Piezo element from a phono cartridge.
This horn will handle over 100 watts rms without crossover! I believe I'm onto something. I would be fun if it works.
Keep the finger crossed...
PETE