Have you checked the actual tracking force of the tonearm with the cartridge?  Don't just go by what it is set at. Actually measure the weight with a stylus gauge.

Sounds more like a burned lamp in the tracking opto.
This opto sits inside a black plastic housing at the foot of the carriage.
An interrupter (metal arm) goes through a slot in the top part of the housing, swinging together with
the tonearm to interrupt light from the lamp shining onto the sensor, both inside the plastic housing.

Under normal circumstances, with the metal covers off the Beogram, you should be able to see
the light from the lamp shine out fmo the plastic housing. 

Martin

Martin, thanks for the reply, yes the lamp is illuminated. And the tracking force was checked with the B&O gauge. When the arm

begins its movement to the left does it not activate a contact that starts pulsing   the carriage motor to track?

Just to make sure that we are talking about the same lamp;
It's a common mistake that the light that shines down onto the record surface has anything to do with the tracking of the recird grooves.
It's only function is to determine if a record is present - and its size.

The tracking takes place at the foot of the carriage.
The "contact" you mention is in fact an optical "contact";
Inside a plastic housing (we are now below decks - at the foot of the carriage), shielded from ambient light, a lamp
shines onto a sensor.
Between the lamp and the sensor a metal arm (still below decks) can interrupt the light according to the arms angle.
The arms angle is determined by the angle of the tonearm (above decks).

When correctly adjusted, as the tonearm tracks the record grooves it moves away from being tangential to the
record grooves (away from parallel to the deck).
This causes the sensor light to be interrupted which in turn causes the servo motor to start rotating to allow
the carriage to "catch up" and make the tonearm tangential to the record grooves again.

I am talking about the lamp inside this plastic housing. Not the lamp inside the arm next to the tonearm.

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Martin

Martin many thanks, I will check the one indicated. I was initially referring to the one that shines through the plastic ruler( seen in the pic parallel to your arrow. Did not even realize that there was another lamp and sensor under the tone arm I thought the lever operated contacts down there. Other than the disassembly of the tone arm is this difficult to replace.  

Martin, Bingo! The lamp does not illuminate. Shinning a small pen light through the slot causes the arm to begin movement. So that checks out.  The lamp seems to be soldered in or IS that a socket in the lid (cover) of the lamp assembly. The circuit board is showing that is a 24V lead going to the lamp. Next and last question what is a good source for this lamp?  My hats off to you sir you do know these machines. I watched a demo of a 4002 TT in 1975 and was in awe at the time however could not afford it (along with the power amp preamp and tape deck) that I purchased at the time wanted one ever since. Many thanks for your help.

It can be a socket or it can be soldered, depending on the version.
If you can provide a photo, maybe we can see what type you have.

Martin

Here is the picture of the underside of the cover with the bulb. Is it possible to test the bulb say with a small

battery to verify its function and rule out another circuit issue?  On the circuit board the lead going to the bulb indicates

24v.

With a DC voltmeter, you can measure the voltage across the lamp when it is supposed to light up.
If you have voltage but no light the lamp is defect.
If you have no voltage, the fault lies elsewhere.

Martin