My suggestion for a reverse wired variac could be dangerous if you don't know exactly what you are doing
Here are a couple less risky alternatives (no risk to the variac etc!)
1. Rewire for 120V and use an variac the normal way around.
I've been told that it is possible to rewire the connections on a 401 motor for 120V operation (I've not personally seen this, but then I haven't looked either). Then use a variac the normal way, wiring the ends of the variac to 0 and 120V and the motor to 0 and the wiper.
My only concern with this is ensuring the motor will have sufficient torque at the sub 120V. Since I don't have a Garrard 401 with induction motor, I can't check it out.
2. Get a Step up transformer and use a variac the normal way to reduce the voltage
This way you can leave the motor connections alone. Then you can get a step up transformer to take the 120 up to 240V and then use a variac in the normal way to bring it down to a lower and slower value.
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Both of these pose less risk of poppencorken, blowenfusen etc!
Step up and variacs rated at about 250-500W should be finea
Here are a couple less risky alternatives (no risk to the variac etc!)
1. Rewire for 120V and use an variac the normal way around.
I've been told that it is possible to rewire the connections on a 401 motor for 120V operation (I've not personally seen this, but then I haven't looked either). Then use a variac the normal way, wiring the ends of the variac to 0 and 120V and the motor to 0 and the wiper.
My only concern with this is ensuring the motor will have sufficient torque at the sub 120V. Since I don't have a Garrard 401 with induction motor, I can't check it out.
2. Get a Step up transformer and use a variac the normal way to reduce the voltage
This way you can leave the motor connections alone. Then you can get a step up transformer to take the 120 up to 240V and then use a variac in the normal way to bring it down to a lower and slower value.
-----------
Both of these pose less risk of poppencorken, blowenfusen etc!
Step up and variacs rated at about 250-500W should be finea
All the Garrards I've seen could be configured to run from 120V or 240V simply by changing links under the motor's mains connection cover. I believe there are some people who say that a 401 configured for 120V and driven from 120V sounds better than one configured for 240V and driven from 240V.
While the motor is a shaded pole induction motor, and as was pointed out to me that at 50Hz it runs at about 1475 RPM and at 60Hz it runs at about 1770 RPM, there remains sufficient torque to cope at lower voltage.
Now people familiar with motors will shout that the increased speed slip that the lower voltage induces will make the motor run hotter. This is strictly true, but for the fact that the amount of iron and copper in the motor is designed for 50Hz. Running at 60Hz actually makes the motor more efficient (and if run at 60Hz would actually run much cooler!), therefore the net effect is little difference.
Many years ago, while I was at University, our campus radio station ended up running on modified square wave power at times because of a series of rotating power outages. The turntables with shaded pole induction motors ran just fine. Microphone circuits were the only ones that complained with a bit of buzz.
We have a box fan that we ran during the hot summers BAC (before AirConditioning) that was TOOOOOOO noisy during sleep. So we put it on a variac and slowed it down at night. That motor did run warm since it was designed for 60Hz, but not excessively hot.
Now people familiar with motors will shout that the increased speed slip that the lower voltage induces will make the motor run hotter. This is strictly true, but for the fact that the amount of iron and copper in the motor is designed for 50Hz. Running at 60Hz actually makes the motor more efficient (and if run at 60Hz would actually run much cooler!), therefore the net effect is little difference.
Many years ago, while I was at University, our campus radio station ended up running on modified square wave power at times because of a series of rotating power outages. The turntables with shaded pole induction motors ran just fine. Microphone circuits were the only ones that complained with a bit of buzz.
We have a box fan that we ran during the hot summers BAC (before AirConditioning) that was TOOOOOOO noisy during sleep. So we put it on a variac and slowed it down at night. That motor did run warm since it was designed for 60Hz, but not excessively hot.
Why Variac
Why would one use a variac to get the right voltage
Before the power op-amp is a pot. With this you'll set the voltage which goes into the step-up transformer, and with that also the voltage which comes out.
In this way I adjusted the voltage to my thorens to something which gives me adequate torque and silent running.
Am I missing something?
cheers, MArco
Why would one use a variac to get the right voltage
Before the power op-amp is a pot. With this you'll set the voltage which goes into the step-up transformer, and with that also the voltage which comes out.
In this way I adjusted the voltage to my thorens to something which gives me adequate torque and silent running.
Am I missing something?
cheers, MArco
Yup you are ... You can run the motor directly off the 60Hz mains without creating an electronic speed control by using a variac.
As explained, although these are synchronous shaded pole induction motors, when fed from a 60Hz source, they can be slowed by lowering the voltage with enough stability and accuracy. No need at all for creating a special power supply to generate 50Hz.
You can't go the other way though! More volts won't make them run faster!!!!
As explained, although these are synchronous shaded pole induction motors, when fed from a 60Hz source, they can be slowed by lowering the voltage with enough stability and accuracy. No need at all for creating a special power supply to generate 50Hz.
You can't go the other way though! More volts won't make them run faster!!!!
Glad you like it. With the right LED it is very bright and perfectly visible even in bright (British) sunshine with the strobe positioned 6" from the platter. Have a look for LEDs where the brightness is measured in cd rather than mcd. I use a red LED that claims about 6500mcd (6.5cd) and allows me to run the thing off a pair of AA cells continuously for over a week.
Cheap Garrard Power Supply
I have experienced that feeding my Garrard 401 with 200VAC lowers the noise from the motor without sacrificing any dynamics from the player. I include a circuit for optaining 200V from a 30V transformator by reducing the 230 voltage by 30V. Hope someone like this simple circuit. Only make shure that the 30V secondary voltage is reducing the 230V voltage and not increasing it. The same can be done using a 15V transformator with a 115V primary winding. The transformator has to be rated at 20VA or more.
I have experienced that feeding my Garrard 401 with 200VAC lowers the noise from the motor without sacrificing any dynamics from the player. I include a circuit for optaining 200V from a 30V transformator by reducing the 230 voltage by 30V. Hope someone like this simple circuit. Only make shure that the 30V secondary voltage is reducing the 230V voltage and not increasing it. The same can be done using a 15V transformator with a 115V primary winding. The transformator has to be rated at 20VA or more.
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