Bang & Olufsen 4002 Turntable arm not lowering - UK Vintage Radio Repair and Restoration Discussion Forum

murphy512 · 24th Oct 2020, 9:06 pm

I am trying to fix this turntable for a friend of mine.
I do not have experience of turntables and this one seems rather complicated.
The controls seem to work, but the arm would not lower.
Has anybody had this problem and managed to fix it.
Any help will be greatly appreciate.
Thanks
Aldo

Radio Wrangler · 24th Oct 2020, 9:09 pm

THere is a solenoid which raises the arm or allows it to drop at a rate controlled by a dashpot.

With the arms moved over a rotating record press up and down, you should hear the solenoid make a 'clack' noise if so and the arm doesn't lower, then you've likely got a gummed up dashpot.

The wood trim around the front and sides is a one-piece assembly. It slides towards you as you look normally at the turntable. It takes a fair amount of force and only slides about 30mm.

With the trim slid towards you, the aluminium plates on top are released. The big plate with the hole for the platter can be lifted and unhooked. The rectangular plate beyond the position scale lifts at its right hand edge and unhooks.

Protect the stylus or unplug the cartridge, these are UNBELIEVABLY expensive. Underneath there are fixings at the rear which release the lid and the rear upstand of the plinth. Now the aluminium cover can be unfastened from the pivot end of the arms. Inside here is the solenoid and dashpot.

"Rather complicated" is an amazing understatement.

I have the 4000 which has a number of differences.

David

Michael Maurice · 24th Oct 2020, 9:15 pm

It probably won't be the dashpot itself. If you look at the mechanism you’ll see that the solenoid and dashpot are connected by a lever which is pivoted. It is this pivot that causes the problem.

As you have gathered these turntables are complex, be very careful.

murphy512 · 25th Oct 2020, 2:33 pm

I have dismantled the solenoid, cleaned and lubricated all associated parts and the arm is now working.
The problem now is that the arm is sliding down the record.
I have watched a video and it shows that the motor driving the arm turns a little every few seconds. Mine keeps on turning continuously.
Getting even more complicated now!
Any idea?
Thank you
Aldo

Michael Maurice · 25th Oct 2020, 8:22 pm

There is a lamp inside that mechanism which detects when the arm has moved slightly. It will need replacing.

Radio Wrangler · 25th Oct 2020, 9:07 pm

I think they use the same type of bulb for the speed indicators and the one in the sensing arm, so maybe a temporary transplant could allow diagnosis.

Also you'll find the motor to leadscrew belt gets elongated and loses grip if you're checking things in this area.

David

PWH · 27th Oct 2020, 7:20 am

If the lamp Michael mentions is glowing, then the part that goes round it that blocks the light is misaligned. It has to be absolutely precise or the arm will keep going or lag behind if it is too far forward/behind.. The manual is available free on the web if you search and all the alignment procedures are in there.

murphy512 · 27th Oct 2020, 11:44 pm

I have finally succeeded in sorting out the problem.
As PWH mentioned, the arm has to be absolutely precise and if it has moved even slightly right or left it will not work. In fact it was not working again after reassembling the unit, but after realigning the arm it worked.

I think my friend will be very pleased with the result and I am very relieved that I managed to repair it without damaging the cartridge.
I was shocked when I noticed the price of a used one!

Thank you all for your advice.
Aldo

24th Oct 2020, 9:06 pm	#1
murphy512 Pentode Join Date: Mar 2008 Location: London, UK. Posts: 122	Bang & Olufsen 4002 Turntable arm not lowering I am trying to fix this turntable for a friend of mine. I do not have experience of turntables and this one seems rather complicated. The controls seem to work, but the arm would not lower. Has anybody had this problem and managed to fix it. Any help will be greatly appreciate. Thanks Aldo Attached Thumbnails

24th Oct 2020, 9:09 pm	#2
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,876	Re: Bang & Olufsen 4002 Turntable arm not lowering THere is a solenoid which raises the arm or allows it to drop at a rate controlled by a dashpot. With the arms moved over a rotating record press up and down, you should hear the solenoid make a 'clack' noise if so and the arm doesn't lower, then you've likely got a gummed up dashpot. The wood trim around the front and sides is a one-piece assembly. It slides towards you as you look normally at the turntable. It takes a fair amount of force and only slides about 30mm. With the trim slid towards you, the aluminium plates on top are released. The big plate with the hole for the platter can be lifted and unhooked. The rectangular plate beyond the position scale lifts at its right hand edge and unhooks. Protect the stylus or unplug the cartridge, these are UNBELIEVABLY expensive. Underneath there are fixings at the rear which release the lid and the rear upstand of the plinth. Now the aluminium cover can be unfastened from the pivot end of the arms. Inside here is the solenoid and dashpot. "Rather complicated" is an amazing understatement. I have the 4000 which has a number of differences. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

24th Oct 2020, 9:15 pm	#3
Michael Maurice Moderator Join Date: Feb 2006 Location: Wembley, Middlesex Posts: 7,224	Re: Bang & Olufsen 4002 Turntable arm not lowering It probably won't be the dashpot itself. If you look at the mechanism you’ll see that the solenoid and dashpot are connected by a lever which is pivoted. It is this pivot that causes the problem. As you have gathered these turntables are complex, be very careful. __________________ Forum Moderator http://www.michaelmauricerepairs.co.uk/

25th Oct 2020, 2:33 pm	#4
murphy512 Pentode Join Date: Mar 2008 Location: London, UK. Posts: 122	Re: Bang & Olufsen 4002 Turntable arm not lowering I have dismantled the solenoid, cleaned and lubricated all associated parts and the arm is now working. The problem now is that the arm is sliding down the record. I have watched a video and it shows that the motor driving the arm turns a little every few seconds. Mine keeps on turning continuously. Getting even more complicated now! Any idea? Thank you Aldo

25th Oct 2020, 8:22 pm	#5
Michael Maurice Moderator Join Date: Feb 2006 Location: Wembley, Middlesex Posts: 7,224	Re: Bang & Olufsen 4002 Turntable arm not lowering There is a lamp inside that mechanism which detects when the arm has moved slightly. It will need replacing. __________________ Forum Moderator http://www.michaelmauricerepairs.co.uk/

25th Oct 2020, 9:07 pm	#6
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,876	Re: Bang & Olufsen 4002 Turntable arm not lowering I think they use the same type of bulb for the speed indicators and the one in the sensing arm, so maybe a temporary transplant could allow diagnosis. Also you'll find the motor to leadscrew belt gets elongated and loses grip if you're checking things in this area. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

27th Oct 2020, 7:20 am	#7
PWH Heptode Join Date: Mar 2003 Location: Waiheke Island, New Zealand Posts: 503	Re: Bang & Olufsen 4002 Turntable arm not lowering If the lamp Michael mentions is glowing, then the part that goes round it that blocks the light is misaligned. It has to be absolutely precise or the arm will keep going or lag behind if it is too far forward/behind.. The manual is available free on the web if you search and all the alignment procedures are in there.

27th Oct 2020, 11:44 pm	#8
murphy512 Pentode Join Date: Mar 2008 Location: London, UK. Posts: 122	Re: Bang & Olufsen 4002 Turntable arm not lowering I have finally succeeded in sorting out the problem. As PWH mentioned, the arm has to be absolutely precise and if it has moved even slightly right or left it will not work. In fact it was not working again after reassembling the unit, but after realigning the arm it worked. I think my friend will be very pleased with the result and I am very relieved that I managed to repair it without damaging the cartridge. I was shocked when I noticed the price of a used one! Thank you all for your advice. Aldo