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Raka 29th November 2002 07:08 AM

Change in frequency mains
 
Hi all,

I have a thorens TD160 and a TD295 MKII turntables, but they were bought in the USA, where the mains is 60Hz, and here I have 50Hz. What can I do? PLEASE HELP ME, BUAAAAHHHHH?

Christer 29th November 2002 07:19 AM

I guess the simplest solution would be to try finding a 50Hz
motor. Check out what a spare motor would cost, although it
would probably be quite expensive. A better way may be to
track down a whole TT that somebody doesn't use anymore.
If you get a functional one cheap, then fine, otherwise, if it
is not working but the motor is OK, then you can probably make
a good deal.

Other alternative, build an electronic motor control.

Raka 27th December 2002 07:52 AM

Freq. converter
 
Hi,

I've found this in another thread:

Quote
A simple Wien-bridge using opamp (1/2 of 5532) and a pair of low power PNP/NPN transistors driving a step-up ( 10:200) transformer. The dc supply to the opamp and PNP/NPN is +/- 15 volt.
The output frequency is adjusted to 50 Hz by adjusting the R in the RC Wien-bridge. The output voltage is adjusted to 110 volt by adjusting the R in the amplitude-ratio (R-ratio) of the Wien-bridge. The output power is about 1 to 1.5 watt which is enough for the TD160 motor.
The output waveform is as sinusoidal as my signal generator and is very stable. TD160 runs happier with this electronic 50Hz supply than a raw 50 Hz supply. It does give a better sonic effect to my system.
Unquote

MAybe this is my solution!! Does anyone know how this works? Any scheme? What is a Wien-bridge?

Thanks

analog_sa 27th December 2002 10:06 AM

Easiest solution is probably to change the pulley to one for 50Hz. Very likely the motor can be set to work at 220v. That said you'll get a much improved sound if you build a low-distortion oscillator. Wien bridge is fine if you don't mind lo-tech and don't require a variable frequency. Any electronics textbook will teach you how to calculate the values. Use low pass filter and a chip-amp/STK module before the transformer. This was the first PS i built and it still works fine. Then i got a bit more enthusiastic and replaced the Wien bridge with an 8015 AVR which generates the sine out of a look-up table, then a DAC and a more complex lo-pass. Is it worth the trouble? Probably not as then you have to deal with filtering digital noise as well.

cheers

peter

analog_sa 27th December 2002 10:12 AM

And another thing. The example above with the 5532/complementary pair is not a very good idea. You should get as high an output voltage as possible before the step-up transformer. This will alow you to use a step-up with a low ratio and minimise the transformer distortion.
The digital approach also allows for easy generation of a second phase-shifted wave if you decide to drive each winding of the motor directly instead of relying on the capacitor.

cheers

peter

Raka 27th December 2002 10:53 AM

Improvements?
 
Hi,

Thanks for your reply. I can't find any pulley, so I have to search more about oscillators. Besides, It will be more fun. Do you think the mains is so dirty that the wein bridge will improve sonics?

peranders 27th December 2002 11:37 AM

Re: Change in frequency mains
 
Quote:

Originally posted by Raka
Hi all,

I have a thorens TD160 and a TD295 MKII turntables, but they were bought in the USA, where the mains is 60Hz, and here I have 50Hz. What can I do? PLEASE HELP ME, BUAAAAHHHHH?

Have you checked SAIA synchrone motors? Maybe they'll fit? Check SAIA's website.

Which speed? Is it 250 rpm (24-pole)? Could also try this (just the motor).
http://www.elfa.se/elfa/produkter/se...htm?_54_490_12

Raka 27th December 2002 02:17 PM

Pulley dismountling
 
Thanks for the links

If I decide to change the pulley, I'll have to dismount the pulley from the original motor, won't I? I tried to do it with a tape deck motor lying around, thinking that the pulley system would be the same, and I couldn't. I didn't see anything to catch, no screws. I tried and tried, but all I got was a broken rotor. :bawling:

Does anyone know how to do this with a thorens motor?

dhaen 30th December 2002 12:03 PM

I don't know about this particular motor, but my experience suggests that the pulley was probably "heat shrunk" onto the shaft.
I so, you'll have to cut it off, as heating may damage the motor.
Fitting a new one won't have the same problem. You can heat the pulley alone, then drop it onto the shaft. Make sure to get the position exact - no second chance.:xeye:
Good luck.;)

Raka 30th December 2002 12:11 PM

Lucky this time
 
Yes, I was because the pulley has a couple of screws and goes out easily. One point for Thorens!
All I have to do now is to discover the poles must have the spare motor.

Nevertheless, the wien bridge is appealing to me. Why the 5532 is not a good solution? I have to step up to 110V so a 10:1 ratio will be enough. Has anyone implemented this option?


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