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Dr. Know is our resident Technical guru, responsible for the free Reference Library, Technical Info, Data Sheets and the Audio Clinic. Contact the Audio Clinic at dr.know@gbaudio.co.uk 

This site has gained an award from the Stagelink Online Directory resource. They awarded a "Recommended" status for Dr. Know's "excellent Reference Library" from 2004 - 2015. 

Your Questions about turntables:

1. Where can I get a new turntable drive belt?
2. Choosing a suitable turntable cartridge
3. Vibration/hum on Pioneer turntable
4. My turntable is running slow
5. My turntable is running fast
6. Why is my turntable humming?
7. Record deck is hardly audible. What's wrong?

8. When should I lubricate the main bearing?
9. How do I lubricate the motor?
10. How can I clean up a melted drive belt?


Q1 Where can I find a new drive belt for my beloved old Dual record deck?    C.B.

Dr. Know's reply: We have a large range of replacement drive belts available by mail / email / telephone order. See the chart and measurement guide on our Drive Belt Data Sheet    top


Q2 I have a Pioneer PL12D deck, which I am recussitating so that I can digitise my old LPs.  I reckon the cartridge and stylus are probably knackered - which one of the cartridges you sell would you recommend for use with this deck? Also do you sell the rubber band that drives it - the one I have still works, but feels a bit crunchy! looking forward to your reply. regards, M.

Dr. Know's reply: Yes we sell a replacement drive belt for the PL12D. The AT95E, AT110E and AT120E/T are all suitable for the PL12D, depending what your budget will allow. The principle difference between them is the output efficiency. The higher output improves the signal-to-noise ratio as you go up the range. That results in a cleaner, quieter sound.  

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Q3 I have replaced the drive belt of a Pioneer PL-512 turntable but now there is vibration through the tone arm when the turntable is set in motion which causes a hum when playing records. I had thought it might be that the drive belt is too tight but I've tried two slightly different belts and it hasn't made any difference. Could it be a problem with motor bearings? Thanks, D.N.

Dr. Know's reply: Hum and vibration are two distinctly different issues. Hum is electrically generated noise, either picked up by the player or noise induced on to the connecting leads and then amplified by the amplifier. Vibration or resonance is a mechanical issue which can manifest itself as a sort of buzzing or humming noise. To clarify the exact nature of your problem, we suggest you check all the following points:

1. Is the hum present even before you turn on the turntable motor? If "yes", check that the tonearm earth wire is connected to the amplifier earth post.
2. If there is still hum, check that the cartridge wiring to the headshell is colour-correct and all wires are well connected.
3. How is the turntable supported? It must be level and without wobble. Then there are two schools of thought about the support structure. Briefly, it should be either a firm, lightweight, low mass shelf (eg 12mm plywood) or a high density, heavy, high mass base (eg marble slab).
4. Check the tonearm bearings. The arm should move smoothly horizontally and vertically with no play on the bearings. If the arm is sticky or wobbly, the bearings may be damaged or worn and will probably need replacing as they are usually not user-serviceable.

For the next check points you will need to remove the rubber mat and platter.

5. Does the deck vibrate when you switch the motor on? If "yes", go to point 8.
6. Does the motor pulley turn easily between finger and thumb, when switched off? If "no", the motor may need lubricating with a high viscosity, heavy duty motor oil intended for high speed shaft application. It should be non-evaporative, non-foaming and with good temperature stability.
7. Does the centre spindle turn easily and smoothly between thumb and finger? If "no", the spindle may need lubricating with light oil designed for low friction areas. It should be a non-evaporative, non-gumming type.
8. What condition are the motor rubber mounting bushes? If they are hard, cracked or perished they need replacing to isolate the motor from the plinth - and stop motor vibration transmitting to the tone arm. 

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Q4. I have replaced the drive belt on my old turntable and it is still running slow. What am I doing wrong?

Dr. Know's reply: We’re sorry to hear that your turntable is not running well with the belt we supplied. Before you return the belt it would be worth checking the following points:

1. Is the drive belt tension correct? If it is slack or slipping, that would account for the speed running slow and the solution is to select a shorter, tighter drive belt. See our guide to calculating the correct drive belt length at www.gbaudio.co.uk/data/belts.htm
2. If the tension is correct, then you should check that the belt is correctly lined up – running on the centre (widest part) of the barrel-shaped motor pulley and not fouling on the mechanical speed-change arm.
3. The motor may be seized up; with the platter removed, check that the motor pulley turns easily between finger and thumb, when switched off? If "no", the motor may need lubricating with a high viscosity, heavy duty motor oil intended for high speed shaft application. It should be non-evaporative, non-foaming and with good temperature stability.
4. The centre spindle bearing may be seized up; with the platter removed, check that the centre spindle turns easily and smoothly between thumb and finger? If "no", the spindle may need lubricating with light oil designed for low friction areas. It should be a non-evaporative, non-gumming type.
5. Certain turntables have an electronically controlled DC motor, rather than a mechanical shifter to change the speed. These models may have a “fine tune” speed adjustment under the platter which is normally accessed with a preset adjuster tool (or a mini screwdriver).
 

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Q5. I have an old belt drive turntable [MICRO] which I recently purchased a replacement belt for, from yourselves, which arrived promptly thank you.
Unfortunately the turntable revolves too fast at 33 rpm. Regards, J B

Dr. Know's reply: Sorry to hear you are having problems with your turntable. From the measurements you gave, we would agree that BELT435 is the correct length. The length of the belt does not have any effect on the speed, however, the belt width can sometimes be a factor if the belt is so wide that it fouls on the motor pulley or other mechanical parts. It would be a good idea to check if the belt is correctly lined up on the motor pulley and clearing the speed changer lever. Also check that the old belt has not left any deposits stuck on the motor pulley because this would cause it to run fast. If there is any old black rubber mess stuck to the pulley, clean it off with solvent eg Isopropyl Alcohol (IPA) cleaner or methylated spirits or nail polish remover.

On an AC motor, this is usually a slightly convex (barrel shape) brass spindle with two stepped levels. The speed selector switch is usually linked to a mechanical arm under the platter with two guide prongs at the end near the motor pulley, which lifts the belt up or down onto one or other pulley.

When the belt is running on the fatter (lower) part it will turn the platter at 45rpm, whilst on the smaller (top) part it will turn the platter at 33rpm. The spindle will often have a top and bottom flange to prevent the belt from slipping off the motor pulley. I would guess that your belt is dropping on to the lower flange which is effectively gearing up the platter and causing it to run faster.

With the power switched off, remove the rubber mat and look at the motor pulley through the inspection hole in the platter. If the belt is running too low on the pulley, you will need to lift the platter off the centre spindle and slip the belt up the drive hub a few millimetres. Refit the platter and stretch the belt over the motor pulley, taking care to route it through the prongs of the speed changer arm. This should solve the problem.   

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Q6. there is some buzzing interference which increases in loudness as the amplifier (Quad) volume is turned up. Any ideas? N.C.

Dr. Know's reply: Your buzz is quite possibly an earthing issue, meaning that the signal cable is not properly screened against interference. Alternatively it could be picking up mains interference by induction from a strong electro-magnetic field (EMF). Here are the main points to check:

Earthing:
1. Check that the four cartridge wires are correctly orientated according to colour.
2. Using a continuity meter, check that the earth wire (beside the phono lead) is well connected to the tonearm tube.
3. Make sure that this earth wire is well connected to the special turntable earth point on the amplifier.
4. Make sure that the amplifier is properly earthed to its mains plug.
5. Check that the earth/screen is well connected on each of the phono connector plugs.

Induction:
1.
Check that the phono lead is not routed next to any mains cables or power supplies.
2.
Check that there are no mains leads or power supplies sitting close to the rear of the amplifier.    
 

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Q7. My vinyl record deck is hardly audible when i connect it to my hi-fi amp. What's wrong? B.C.

Dr. Know's reply: There are a few common issues when connecting up turntables, mostly to do with gain matching. Here are the main points to check:

Cartridge/Stylus:
1. Check that the four cartridge wires are correctly orientated according to colour.
2. Check that the phono cable screen is well connected to the phono plugs. A good earth connection is essential for proper screening against noise and also as the reference for the signal. Without a good earth/screen the sound will be unstable.
3. Check that the stylus tip is not broken off or the cantilever tube its mounted on is not bent or damaged.

Level Matching:
1.
Most old school hi-fi amplifiers or pre-amps have a turntable or "phono" input. This gives the correct level and impedance matching for a moving magnet cartridge. Always use this input for your turntable and always connect the little earth wire to the turntable earth terminal on the back of the amp.
2.
More recent amplifiers only have line level inputs. The connectors are the same but they will only work with sources which produce standard line level signal such as CD players, DVD, MD, tape, cassette, MP3, iPod docks. This is the same for PCs with a 3.5mm mini jack line input. If you connect a turntable to a line level input you will only get a barely audible signal because the cartridge output is tiny (typically about 5 millivolts) compared to a standard line level (typically 775 millivolts). However, it is possible to connect a turntable to a line or aux input using a phono pre-amp such as the BT26, which boosts the low cartridge output up to a standard line level. These can be mains or battery powered.
3. Alternatively, you can use a digital convertor such as the AC-1 which combines both phono pre-amp and digital conversion in one unit and connects to a PC or laptop via USB.
4. A digital convertor is also the perfect solution for connecting a turntable to a laptop which has no line input socket.  
 
 

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Q8  When should I lubricate the main bearing on my turntable?

Dr. Know's reply: Remove the platter and check if the centre spindle turns easily and smoothly between thumb and finger? If "yes", your bearing does not need to be lubricated. If there feels to be any resistance, stickiness or roughness, the spindle may need lubricating with light oil designed for low friction areas. It should be a non-evaporative, non-gumming type, like sewing machine oil for example, not WD40.

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Q9. How do I lubricate the motor?

Dr. Know's reply: Remove the platter and check that the motor pulley turns easily between finger and thumb, when switched off? If "yes", your motor does not need to be lubricated. If "no", the motor may need lubricating with a high viscosity, heavy duty motor oil intended for high speed shaft application. It should be non-evaporative, non-foaming and with good temperature stability.

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Q10. My old belt has melted into a blob of sticky tar. How can I clean it up?

Dr. Know's reply: Depending on the conditions in which a turntable deck has been stored, sometimes drive belts will dry out and crack or snap and sometimes they will "melt" into a tarry mess which sticks to the platter, and motor and may even drip on to the sub-chassis. Before installing a new drive belt, check that the old belt has not left any sticky black deposits on the platter or motor pulley because this could affect the playing speed and create wow & flutter. The motor pulley should look like clean, shiny brass or steel. If there is any old black rubber mess stuck to the pulley, clean it off with solvent eg Isopropyl Alcohol (IPA) cleaner or methylated spirits or nail polish remover. Ensure that all drive surfaces are clean and free from any tarnishing before installing the new drive belt.    

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Dr. Know aims to reply individually to your sound system queries sent to his Audio Clinic. No appointments necessary. Some queries may be published.

Unsolicited Customer Quotes: 

"Thanks again for your quick response... I found you on the Web using Firefox/Google. I was impressed by the detailed information and range of products on your web site... I think your web site and the service you provide is first class. Regards" Anna (13/01/2014)

"Hello... I would like to say thank you for helping me get the right belt for my turntable and the stylus as well. It is a pleasure to put my lp's on again and listen to music I thought would be lost. Wishing you a merry Christmas and a happy new year." M Albus  (16/12/2013)

"Excellent quick service and help getting a belt that worked on my deck. Thanks to you my old Pioneer deck lives to play again." RW Sussex (10/12/2013)

"To thank you for the excellent turnaround on the item I purchased on Tuesday January 3rd. - an item which I ordered on your advice. It was delivered on Monday 9th. which, considering that Friday 6th was a national holiday here in Spain was sooner than I expected. The item is working perfectly. Many thanks". E Robinson (11/01/2012)

"Dr Know, Thank you for your time and for your wise advices". Gauthier (15/11/2011)

"That's brilliant! Thank you so much for the excent and speedy service. Best wishes," Lance. (03/09/2011)

"Dear Dr Know, Many thanks for your prompt and reassuring reply. Best wishes, B Bensley" (05/02/2010)

"I would just like to say that when I did a uk google search (drive belt), your site was the easiest to use and understand, with good, clear insructions. I especially liked the link to Pi, it made me smile". Best wishes, Ben UK (26/03/2009)

"hi, just bumped into your web site (through a search on some microphone specs i think) and its really nice. if more people actually put up some useful information on their sites then the web would be a better place..."  a.f. brussels

 

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