After the tonearm sets down on the record the sensor arm doesn't move across the disc.

Reply

mfcole Posted: Wed, Oct 6 2021 10:15 PM

rated by 0 users

Hello Beoworld,

I hope someone can help me with the following problem with my 4002 turntable.  After the tonearm sets down on the record the sensor arm doesn't move across the disc.  Thus, the tonearm is carried towards the sensor arm by virtue of the record grooves.  Once the tonearm sets down on the record the motor diving the platen supporting the tonearm and sensor arm does not run.  I assume that the platen must move to allow the tonearm/sensor arm complex to move across the record.

All help/advise appreciated.

Mike

Reply

sonavor replied on Thu, Oct 7 2021 3:29 AM

rated by 0 users

Hi,

The Beogram 4002 is an analog control system (meaning no digital computer controlling it :-) ).  
B&O engineers use a couple of motors, switches and some light controlled sensors to perform all of the necessary functions of the Beogram 4002.
That is a simplified answer of course but it means that a number of things could affect the problem you are experiencing.

The Beogram tangential arm is controlled by a servo motor (separate from the platter motor).
The fact that your Beogram tonearm moves into position to play indicates the belt for that motor is still attached.
The problem where the servo motor doesn't advance your tonearm could be as simple as the tracking sensor adjustment is way off.
The tracking sensor is one of those light driven sensors I mentioned.  That sensor needs to be calibrated per the service manual to advance the tonearm as it navigates the grooves of a record.
Another possibility with your problem is that the lamp source for that sensor burned out. In that case the tracking cannot be adjusted until the lamp is replaced.

If your Beogram 4002 is still operating on its original, forty plus year old parts then it really requires a complete restoration to return to the operating condition it is capable of.

There are a lot of posts on this forum and on the Beolover Blog that show Beogram 4002 restorations in detail.

-sonavor

Reply

Mark replied on Thu, Oct 7 2021 5:06 PM

rated by 0 users

It could be a couple of items. First I would check to see that the sensor bulb at the base of the tonearm is lit. It is covered over by its black plastic holder but light does leak. If it is then I would look art the shutter adjustment. This is detailed in the service manual and is also illustrated on Rudy’s site at beolover.blogspot.com. If it is neither of these you are going to need to dig into the electronics so check back.