Hi, I am reviving this thread from 2012 since I am experiencing the same problem and no possible solutions were suggested back then.

I recently decided to make all necessary mechanical adjustments to my BG4002 deck as per service manual. All adjustments were made and before putting the deck together I checked the tracking force using my gauge. Then I realized I couldn’t increase the tracking force more than 0.9 gr even when I set the dial knob at 1.5 gr and the counterweight as close to the back of the tone arm as possible.

Is there any way I can increase tension in the torsion spring located behind the little dented gear next to the tracking force bushing so as to increase the tracking force of the tone arm at least up to 1.2 gr? What am I missing here?

It sounds like your counter weight got out of alignment or your tracking force knob gears slipped out of position or are stripped.

Check the back of the tonearm (have to remove the dust cover and the tonearm cover). Look at the counter weight there. It has an adjustment screw that is addressed in the service manual. The manual calls to calibrate it for 0 grams on the tonearm but I typically calibrate mine for the tracking force knob between 1 and 1.2 grams since that is the most used setting. I have seen cases where the tracking force knob (the one with the spring and gears) is loose and doesn't fit snug enough. There is a really tiny set screw for attaching that knob so be very careful when working with it. Also, there is a limit to moving the counter weight in the back. You and extend the counter weight too far (inwards and outwards) where the tonearm function is messed up. There have been a couple of instances where I had to remove the tracking force knob, set the counter weight position where it needed to be, then reattach the tracking force knob. That takes some practice to get right and again, be very careful of the small set screw. Never torque any of the screws. They should gently be set into position.

link I posted shows the tracking force counter weight adjustment screw (about half way down the page).
Beolover has a

Thanks Sonavor! Your thread was among the first I looked at for advice. However, as I wrote before I have already moved the counter weight as close to the tonearm as possible. So, there is no more room for adjustment there. This leaves me with the tracking force knob adjustment which - by the way- seems tight enough, as the only way to increase tracking force. Now, I suppose you are referring to this tiny screw shown in the picture. My only fear is what will happen if I unscrue this tiny screw and remove the knob. Will the tiny torsion spring suddenly unwind? And, finally how can I increase tension in the spring? Just by resetting the counter weight?

Milton

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Sorry for asking, but I have seen many things....
You do have a cartridge fitted - right?

Martin

Of course Martin! I have an MMC 20EN cartridge fitted. I had to repeat all mechanical adjustments on the BG 4002 because I want to use a quite sensitive cartridge ( a refurbished MMC 20CL with a nude Shibata stylus mounted on a beryllium cantilever) and I don't want any unpleasant surprises. All adjustments are now perfect except for the tracking force one. It is so simple yet so puzzling. I will go with Sonavor's advice and hopefully I will not see any springs jumping in the air when I take the knob off!

Have you done the arm lowering limit adjustment? With everything out of the way (platter removed, deck covers removed) and the Beogram power plug not connected, what happens when you manually pull the solenoid lever so the arm can lower? Does it move a little then stop? Double check the lowering limit screw and the lowering damper. Maybe you have one of them set incorrectly. What happens when you manually lower the tonearm (very gently...don't force anything) by hand?  Can you detect an obstruction?

I found an old picture from a Beogram 400x project where I had to reassemble the tonearm from the ground up. This photo shows all of the tonearm tracking force components disassembled. Note that the tonearm counter weight adjustment screw doesn't have the locking nut on it so obviously that will need to already be in place. I am also not 100% sure that is the correct set screw in the photo. However, the photo shows the starting position I usually begin the counter weight and tracking force adjustments at. You can manually turn the tracking force gear that has the spring to where you initially want it, then slide on the adjustment knob (its gears mesh with the spring loaded gear) and screw in the set screw. I will emphasize again not to torque down the set screw. It isn't there to apply downward force. It just fits into the groove of the adjustment knob to keep it from sliding out. 

The tonearm adjustments all affect each other so try and start with things in a neutral position so the components that require adjusting don't have to be adjusted all the way to their limit. The counter weight needs to provide the proper balance to the tonearm for the tracking force gear to allow setting a force from 1.5 grams to 0 grams but it also has to allow free travel when the arm is lowered. To get there might take a few iterations of adjusting...in small steps. I try to calibrate my tracking force adjustment knob where it is as accurate as I can get it between 1.0 and 1.2 grams as that is the most useful range for the cartridges I use.  I hope that helps.

I didn't think the set screw looked right in the previous photo. I found another photo of the same tonearm assembly but with the correct set screw. You can see how small the actual one is. Like I said, it just fits down into the adjustment knob mounting post groove.

Also, regarding the counter weight adjustment screw. There is normally a small, locking clip that is not visible in the photo that holds the adjustment screw in position. I mentioned a locking nut because I take the adjustment screw all the way out and replace the clip with a nut. When I have the weight adjusted where I want it I apply some locking nut fluid to the threads.

One more thing -
Looking at your photo again.... your counter weight looks too far forward. In that position it will hinder the tonearm pivot from lowering.