Studer A807 motor bearings - UK Vintage Radio Repair and Restoration Discussion Forum

Linnovice · 25th Mar 2016, 5:50 pm

Hi all, I've had a problem develop on my Studer. In fast rewind there is a low drone and vibration coming from the left hand spooling motor (supply side). I've stripped out the motor and run it out of the machine and the noise and vibration are there. It's ok on overrun with no load but as soon as the power goes on the drone starts. Question. How difficult is it to change the bearings? Are they readily available?
Also, I noticed when I took the motor out of the chassis that there is a plastic toothed ring on the back of the motor. Mine has one tooth missing, would this effect performance?
Any advice and guidance would be gratefully received. M.

Michael Maurice · 25th Mar 2016, 11:59 pm

As far as I'm aware, the only bearing that is replaceable is the bottom bearing, the top bearing being sintered. it may be that it is this bearing thats causing the problem and putting the correct oil in may solve your problem.

I've no idea what the plastic ring does but I doubt one missing tooth would give you the problems you describe.

joebog1 · 26th Mar 2016, 12:23 am

Sewing machine oil is suitable for the bearing.
Are you sure the "toothed ring" is not the fan ?

When lubricating the motor, one drop is sufficient.
To check whether the bearing is the cause, try and "rock" the motor shaft from side to side. By that I mean push the shaft sideways with your fingers, feeling for any movement. A good bearing will have no movement that is discernible with the fingers.

These motors generally last forever ( almost) and lubrication will be all that is necessary.
One other thing to check is the brake!! make sure it isnt dragging.
Best of luck
Joe

Ted Kendall · 26th Mar 2016, 11:39 am

The toothed ring is for a tacho which feeds the transport software. Whether one broken tooth matters I wouldn't like to say.

flywheel · 26th Mar 2016, 12:39 pm

I don't know the design of A807 motors but this sounds a bit like a problem I've seen a couple of times on other, small tape deck induction motors, where the rotor has slipped slightly on the shaft. When energised, the magnetic 'pull' from the stator then lifts the rotor and shaft so that the bottom end of the shaft bounces against the lower bearing end in a vibrating movement, instead of being slightly thrust against it, as it should when the rotor is correctly positioned.

25th Mar 2016, 5:50 pm	#1
Linnovice Hexode Join Date: Jun 2014 Location: Chelmsford, Essex, UK Posts: 386	Studer A807 motor bearings Hi all, I've had a problem develop on my Studer. In fast rewind there is a low drone and vibration coming from the left hand spooling motor (supply side). I've stripped out the motor and run it out of the machine and the noise and vibration are there. It's ok on overrun with no load but as soon as the power goes on the drone starts. Question. How difficult is it to change the bearings? Are they readily available? Also, I noticed when I took the motor out of the chassis that there is a plastic toothed ring on the back of the motor. Mine has one tooth missing, would this effect performance? Any advice and guidance would be gratefully received. M. __________________ Small Scotch, New Aids and Happy Ears

25th Mar 2016, 11:59 pm	#2
Michael Maurice Moderator Join Date: Feb 2006 Location: Wembley, Middlesex Posts: 7,224	Re: Studer A807 motor bearings As far as I'm aware, the only bearing that is replaceable is the bottom bearing, the top bearing being sintered. it may be that it is this bearing thats causing the problem and putting the correct oil in may solve your problem. I've no idea what the plastic ring does but I doubt one missing tooth would give you the problems you describe. __________________ Forum Moderator http://www.michaelmauricerepairs.co.uk/

26th Mar 2016, 12:23 am	#3
joebog1 Banned Join Date: Jun 2015 Location: Mareeba, North Queensland, Australia Posts: 2,704	Re: Studer A807 motor bearings Sewing machine oil is suitable for the bearing. Are you sure the "toothed ring" is not the fan ? When lubricating the motor, one drop is sufficient. To check whether the bearing is the cause, try and "rock" the motor shaft from side to side. By that I mean push the shaft sideways with your fingers, feeling for any movement. A good bearing will have no movement that is discernible with the fingers. These motors generally last forever ( almost) and lubrication will be all that is necessary. One other thing to check is the brake!! make sure it isnt dragging. Best of luck Joe

26th Mar 2016, 11:39 am	#4
Ted Kendall Dekatron Join Date: Jul 2008 Location: Kington, Herefordshire, UK. Posts: 3,671	Re: Studer A807 motor bearings The toothed ring is for a tacho which feeds the transport software. Whether one broken tooth matters I wouldn't like to say.

26th Mar 2016, 12:39 pm	#5
flywheel Tetrode Join Date: Aug 2005 Location: Leicester, Leicestershire, UK. Posts: 68	Re: Studer A807 motor bearings I don't know the design of A807 motors but this sounds a bit like a problem I've seen a couple of times on other, small tape deck induction motors, where the rotor has slipped slightly on the shaft. When energised, the magnetic 'pull' from the stator then lifts the rotor and shaft so that the bottom end of the shaft bounces against the lower bearing end in a vibrating movement, instead of being slightly thrust against it, as it should when the rotor is correctly positioned. __________________ Andrew B.