AMi K Cut-Off Switch & Bias Spring (900 Mechanism)

Hello again,

I recently replaced the ceramic cartridge in my AMi JBK-120 with a magnetic Pickering NP/AC

I am having difficulty getting it to track properly. Some records play ok but some are skipping. I have spent hours try to find the right balance. The skipping occurs near the end of the record.

Someone suggested that I may be missing the bias spring and that resistance from the cut-off switch was causing the problem. I checked and I don't see any spring near the tone-arm. Is this the spring I need?

[www.jukebox-world.de]

My mechanism model is 900. The Stamann site says the spring will work with mech models 985 & 990. The install picture on the site looks different than mine (Please see pictures) I hope this spring will work.

Also, is my cut-off switch not original? The same person told me that if it is a standard micro-switch, it will have a much higher closing pressure and will choke off the inward movement of the tone arm toward the end of the record

Any help would be greatly appreciated!!

Thanks

Paul

Hello Paul

You have the mono version of the model K. The mono version has no bias spring and therefore is not prepared for the installation of such. For Mono the spring is not necessary.

The cut-off switch could be the cause of your problem. The switch may have been already replaced, the original is black. A very sensitive switch must be used with the lowest possible operating force.

Best regards - charly49

Ahh!! Thank you Thank you!!! That makes sense now

You have saved me again!!

I will order a new cut-off switch tonight

Cheers!!

Paul

Hello Karl,

I purchased and installed the new cut-off switch.

It is better, but I still can't get it to track around 5 grams. Is there anything else I can try? A counter-weight modification? Or maybe somehow modifying my tone-arm and adding a bias-spring?

Thanks,

Paul

Hello Paul

You can increase the tracking force on 6 or 7 grams for testing. If that does not help, there is a different fault. It may be that the pickup - cable is stiffened or badly positioned. It is also possible that the guide plate that moves the tone arm touches the cam of the gripper shaft. This happens sometimes when the Camshaft switch is set incorrectly. If the record is placed, the flat spot of the cam must be absolutely horizontal. There must also a clearance of 1 - 2 mm be present between the cam and the guide plate.

A possible cause would be that the stylus tip bent, worn or damaged. I assume that you are using the original cartridge (GE VRII). If not, it may also be that the cartridge is not suitable for this box.

Last but not least, it is also possible that the micro switch has too high operating force, even if it is referred to as "high sensitive".

Best regards - charly49