AC Turntable Motor Replacement

This article can help you diagnose and solve your AC motor problems.

To simply replace an AC synchronous turntable motor with the same again is not as easy as installing our DC motor kits for the following reasons.

Simple AC synchronous replacement turntable motors are problematic. There are so many derivatives that it can be difficult to specify the exact replacement as they all look similar.

For an AC synchronous turntable motor one needs to fit a pulley of exactly the right diameter and height. This is critical because the diameter dimension  dictates the speed your deck will run at. However it’s not always possible to remove your original pulley because some are press fitted. If this is the case you will need a machine shop to produce a replica pulley for you and this can be expensive.

Even if it is possible to remove the pulley without wrecking it, there is then the problem of fitting it to the new motor shaft. Many motor pulley combinations are precision bored and press-fitted which means that unless one is careful the turntable motor will be wrecked just by putting on the pulley – if pulleys are fastened on with a grub screw then it is likely to have a very slight “wobble” which is extremely detrimental to performance.

Many old decks can be given a huge leap in their performance by upgrading to our DC turntable motor kit – it is difficult to imagine the level of improvement attainable until tried, which is why we offer a money back guarantee.

Excessive Motor Noise

AC synchronous record deck motors usually run silently so motor noise is a sign of worn bushes and the motor will need to be replaced.

Identifying a Worn Cartridge

How to Set-up the Cartridge

Cartridge Alignment Systems

How to Clean Your Cartridge

Cartridge Troubleshooting and Set-up

We understand the frustration that occurs when a system malfunctions. Tonearms need to be set up correctly and are one of the more potentially problematic items of equipment. This is a list of problems and solutions to hopefully get you out of trouble. To save time just skim down the sub-headings till you get to the relevant section for the issue you need an answer for.  These notes contain over 30 years of experience and try to cover every eventuality hence they are extensive.

Please note that once this suggestions on this page have been exhausted and your arm needs fixing, then it should be returned to us.  Professional repair shops and rewiring firms should not carry out the work unless expressly approved by ourselves on a  case by case basis. This policy is not protectionism but to ensure you do not end up with a wrecked arm. Our arms are unique in many respects and outside experts are not familiar with the many pitfalls.

Electrical

Sound Quality

Mechanical

Miscellaneous

Speed Variation Issues

For Turntables Without Light Speed Controller

The following paragraphs outline possible causes for speed problems. Bear in mind that 0.3% fast or slow is not audible for most people and will not affect your enjoyment of the music. To put this in perspective, early Rega decks used to run 1% fast, as it’s harder to tell when something is running fast than when it’s running slow.

• Changing the belt tension will affect the speed instantly. Tension also affects the ability of the motor to maintain speed stability over long periods of use ( e.g 4 to 5 hours of continuous running without stopping). If a belt is too tight or loose, speed drift over time can occur. To solve this, you can experiment with belt tension by changing it a little at a time and recording the distance from the platter centre to the Motor centre. The ideal starting first trial distance is such that with the belt held as loosely as possible over your finger, it should be around 3mm from the near edge of the pulley. This means that when you hook the belt over the pulley, it stretches about 10mm.
  Note that belts stretch a lot in the first 24 hours of use, so if you are using a new belt, allow it to run in first and then reset the tension before finally setting the speed.

• A contaminated belt, pulley or platter can cause speed issues – clean running surfaces with mild soapy water and then rinse or wash off with water.

• After re-oiling a bearing, it usually takes a while to settle down completely. So allow it to run for around 4 hours before setting the speed.

• The power supply takes around 5 hours to warm up and stabilise completely after switching it on at the mains. For this reason, it should be left powered up permanently. As it only consumes about 30mA in standby, this is insignificant.

• Significant changes in room temperature affect the viscosity of the oil in the bearing, so if the room temperature is well outside normal, then the deck will run slightly slow if too cold and fast if too warm.

• Transistors that have developed temperature instability.

Note: For Origin Live decks pre-2008 it is worthwhile changing the oil to our new type – the older oil could dry out or deteriorate if not used regularly which has been known to cause speed problems.

Noisy Motor

If the motor produces a “knocking” noise, it is almost certainly due to overtightening of one or more of the three cross-head screws holding the motor. The underside of each screw head should touch the top of the rubber grommet underneath without compressing it.

If the motor has an unusually noisy “whirring” sound, it is possible that the spindle bearing has developed friction. This should not happen as the bearings are designed to be self-lubricating and run dry. However, it is an explanation, and we have found that a PTFE-loaded oil can reduce spindle noise and may solve speed variation in the odd case (we have seldom seen this to work for long, though). This oil and the video on how to apply it can be found on the link Motor bearing Oil PTFE loaded

The video can be found on the following link: https://www.youtube.com/watch?v=XrMna_UMaxM

Belt pulley with rubber debris buildup

A pulley with rubber embedded on the surface can cause flutter issues. To address this problem you can take the following action.
Note: Many belts (not just ours) leave a black deposit over years of use which means pulleys need to be cleaned every year or so.
a) Remove the belt.
b) Wrap tissue paper around the underside of the pulley to prevent any dust or debris from entering the motor.
c) Run the motor and hold a screwdriver gently against the pulley to wipe off the attached rubber.
d) If this fails to remove everything try using 320 grit sandpaper – this will not harm the pulley.

To clean the belt you must avoid placing any stress on the joint. We suggest gently wiping with soap and water then a thorough rinse in water alone to remove any soap residue.

Avoid the use of powerful solvents like Acetone (nail varnish remover) on the belt and pulley.

Bearing Contamination causing speed variation (highly unlikely if oiled properly)

Check that your bearing is properly oiled.

To further check that the bearing is functioning correctly please see the video on how to check your turntable bearings – https://www.youtube.com/watch?v=NlFotLCS3kA

Sometimes a bearing house needs a good clean and new oil (every 3 – 6 years depending on usage)

Belt Vibrates

This is often caused by oil on the belt or pulley. Clean the belt and pulley with a diluted solution of isopropanol or Acetone (nail varnish remover) – anything which leaves no residue. Soap & water may suffice but you must rinse thoroughly with water afterwards.

Platter Wobble

Hum Problems

See Tonearm Troubleshooting

Noisy Motor

Possibly the spindle bearing has developed friction. This should not happen as the bearings are designed to be self lubricating and run dry. However it is and explanation and we have found that a PTFE loaded oil can reduce spindle noise and may solve speed variation in the odd case (we have seldom found this to work for long though). This oil and the video on how to apply it can be found on the link Motor bearing Oil PTFE loaded

The video can be found on the following link: https://www.youtube.com/watch?v=XrMna_UMaxM

For Setting Up Linn LP12’s

See LP12 Set Up (PDF document)

Foot Fall Problems Causing Stylus To Skip

If your turntable is sited on a wooden floor there are sometimes problems with a heavy footfall causing the stylus to skip in the groove. Sometimes at higher volumes there are also problems of low frequency feedback through the floor causing the headshell end of the arm to oscillate visibly in the groove.

Solution: The most obvious cure all is to place the turntable on a wall shelf (preferably on a solid wall rather than stud partition. However before adopting this course of action there are a couple of other possible solutions.

a. Try moving the table to a different location – even a few inches can make a difference.
b. Try weighting the table down with a heavy object – slab of marble, etc.
c. Try using something like the Seismic sink which is essentially a rubber tyre inflated inside a platform.

Stylus Oscillation

Sometimes at higher volumes there are problems of low frequency feedback through the floor causing the headshell end of the arm to oscillate visibly in the groove. Look to above section for solutions to this problem.

An alternative explanation that has been known to cause this problem is motor vibration caused by a pulley foul or similar problem causing excessive sub-chassis vibration.

Static

For “Popping” Noise Through The Speakers

See Troubleshooting Motors & Power Supplies

Static, causing your turntable mat to lift off with records or give you a shock when touching the headshell

Static problems are aggravated in particular environments. The cause of static can be due to a number of factors and solving any problems. Tracking down the source(s) demands a multi-faceted approach.

Dry atmosphere

Air conditioning often causes problems so a humidifier can help or introduce pot plants with plenty of water.

Synthetic carpets or clothing

Try wearing different footwear. Rubber soled shoes allow you to build up thousands of volts of static. Also check out different clothing. Maybe put a non-synthetic mat where you stand to change your records.

Record sleeves that put static on the record when they are removed

Use genuinely anti-static sleeves. Try anti-static guns that remove static charge from records. Zap guns are available on our website.

Records that have not been cleaned.

We strongly recommend clean your records with L’Art du Son cleaning fluid. This does the job without damaging your records.

Equipment placed on surfaces that have exceptionally high insulation and capacitive characteristics

There may not be much you can do to solve this problem but if experimentation is possible then try a few things.

Earths that are not connected or not functioning

If you have a continuity tester then check that earth leads are working. For example you should get conduction between an exposed metal part on the tonearm and the earth lead on the end. Don’t make the mistake of thinking an anodised part should conduct because it won’t (anodised surfaces are non-conductive).

Solutions:

In the rare occasion that static continues with tonearm earths attachefd and functioning, you can try attaching an earth lead to the bolt on the underside of out turntables bearing house.

Bearing Noise

Very slight bearing noise can sometimes occur – the oil must overflow to eliminate noise. If this does not do the trick then there may be a nick on the shaft perhaps caused by poor handling. Feel the spindle carefully for a rough patch. This can be rectified by lightly using 800 grit wet and dry paper on the defective area only of the shaft. If the defect is a small dent you need not get rid of the whole dent – just abrade the edges to get rid of the raised points.

Marks inside the bearing house can be caused by inserting a spindle at a slight angle but they are very slight and usually bed in with the bearing.

People invariably get focussed on audible noise and producing a silent bearing or motor is EASY. However silent bearings can sound dreadful on audition in comparison to a high rigidity “noisy” design.

Never tamper with the bolt in the bottom of the bearing or oil leaks will occur and you will probably not succeed in re-tightening it.

Motor noise

The “whirring” noise of the motors we use is the noise of brushes contacting the motor rotor and cannot be helped. It’s better to have great electrical contact which improves your motor’s smooth operation even if it results in a slight audible noise. Brushless motors may seem an ideal answer but they are in fact much worse in terms of performance as we’ve tried them. Your cartridge picks up vibration not audible noise and silent motors can have terrible vibration.

Having said this there are sometimes intances where motor develop a kind of “rumbling or grumbling or even knocking noise” This is discussed and a solution put forward in the Youtube video at the bottom of the following link Motor rumble

Hum problems in audio can be notoriously difficult to track down. Usually they result from earth loops between equipment that creates a mains derived voltage oscillation that feeds into the signal path in your amplification. This is then amplified internally by your amplifier to produce hum through your speakers.

Over the years we have compiled a list of the various causes that can give rise to hum problems and their solutions. To save time just skim down the sub-headings till you get to a relevant section.

Electro-Magnetic Interference

Mains cable or transformers and amplifiers in the vicinity of low level signal cable can easily cause hum so ensure the arm cables and any phono stage interconnects and phono stage are spaced well away – you will hear hum diminish as they move so you can judge how far is safe enough.

Connection of earth leads to equipment

Never tamper with earth lead connections from the mains. These are critical to ensure that you are not exposed to lethal electrical shock and they are often essential for equipment to function correctly.

This section deals with separate earth leads that connect to the outside of equipment. These are leads that screw onto a rear binding post on the back of your amp. They may come from a tonearm, turntable, interconnect cable (if it has an external shield) or other item of equipment.

It is usually a bad idea to add a wire to join items of equipment like a pre-amp and power amp but this is a matter of experimentation as to whether it does any good. It should also only be done where a rear binding post exists on the rear panel of any item of equipment. The reasons why some equipment carries an earth terminal and some do not is complex and certainly not something that can be explained here.

Ensure there is no break, bad termination or poor connection in earth wires.

You should also connect external earth wires to different equipment as well as experimenting not connecting it to others. For example the earth lead from a deck or arm is best connected to the phono stage binding post or if you don’t have one, the pre-amp. If you only have an integrated amp there is only one choice so you can’t go wrong.

Deck sub-chassis not earthed to arm

Some decks need an earth connection between their chassis and the tonearm to prevent hum. The Technics 1200 series is one such case. Although Linn decks have this option it is seldom necessary.

Mismatch of Amp Input

If you are using a moving magnet cartridge make sure that the phono stage setting is correctly set for moving magnet input and vice versa for a moving coil cartridge.

Unshielded Cartridges

Grado cartridges are unshielded and this can cause problems with A/C turntable motors which kick out quite a strong magnetic field. The only solution is either to change the cartridge or use a DC motor.

Earth Loops

You can experiment with attaching and detaching earths – particularly if you have a pre-power combination – sometimes it is best not to link the two together by an earth wire.

Fault Within the Cartridge or the Amp

Cartridges can sometimes develop hum as can amplifiers. To eliminate this possibility you can swap channels if the problem is only on one channel and hear the result or you can substitute the cartridge or arm if possible.

Areas of Very High RF

(i.e. residences near radio transmitters –) Try enclosing the cable in a large diameter braid earthed to the arm or pre-amplifier. You can try it in foil but it is limited in its screening effectiveness. Once something works, a more elegant solution can be found – If you are stuck for braid try Maplins.

Earth Lead Connection Between Arm & Deck (Technics 1200 Especially)

When we internally rewire an arm then a separate ground lead is installed which enables easy connection of the arm to earth. However for the OL1 without any modifications, the arm earth is attached to the return signal of the left hand channel i.e the outside metal of the black plug (at the other end – the wire with the blue cartridge tag on the end). Try touching the earth wire from the deck to the outside metal part of the black phono plug with everything playing. If this eliminates hum then you can splice into the arm cable for permanent attachment.

Tonearm Wiring

We test all our arms and rewiring jobs for hum before they are dispatched, however faults can very occasionally develop in transit, fitting or subsequent use. From time to time there is an internal wiring fault that may develop which causes hum – this is something that is often possible for you to rectify. However, before trying to fix or return the arm to us, it is worth listing the other causes of hum – this list is not exhaustive.

Unshielded Cartridges

Grado and Music Maker cartridges can hum when used on turntables which have an A/C synchronous motor not positioned on the far side of the platter. You can either change the cartridge of fit one of our DC motor kits which emit a very low electromagnetic field.

Tonearm interconnect issues

Occasionally there can be an impedance mismatch of tonearm cable litz wire capacitance with the pre-amp input – if you have another pre-amp or can get hold of one it is worth checking this.

Troubleshooting Hi-Fi systems can be tricky. We have compiled information which we hope you’ll find useful and always welcome new contributions.

Troubleshooting Hum

Troubleshooting Turntables

Troubleshooting Tonearms

Troubleshooting Cartridges

Motor and power supplies

Cleaning Records