Gyro SE suspension problem...

I have a Gyro SE MkII with a SME 309 tonearm (purchased 12/2009) and was finding that in order to get the platter level I was having to raise the spring opposite the motor considerably higher than the other two suspension springs. The spring ends up being elongated more than the other two and this affects the “bounce”; that is, I was unable to get a perpendicular bounce because the one spring, because it’s elongated more, does not have the same springiness.

I thought maybe it’s because the one spring had lost some elasticity over time so I ordered a set of replacement springs. Today I replaced the springs but the problem is still there. The one spring suspension “nut” (nylon insert that seats into top of spring) is about 3.5mm higher on the post than the other two in order to level the platter. So the problem wasn’t the spring. Rather, it seems like the weighting of the chassis isn’t correct; as though the wrong weights were used in the chassis, especially the weight located at the motor opening. The problem is present when 1) only the chassis is in place, and 2) the platter is in place; the problem worsens when the platter is installed. This is both discouraging and irritating, since I paid $139 USD for the replacement springs and the problem is still there.

Some background:
- I ordered the turntable with a SME arm adapter plate and assume that I received the correct plate with the correct weight for the SME 309.
- The acrylic “plinth” was leveled prior to installing the suspension towers, chassis, and platter.
- I was careful inserting the nylon inserts into the springs, making sure I did not stretch the springs.
- I checked that all the suspension tower thrust balls were in place in and in the correct position.
- I checked that the white spacers were in the correct position and the spring assemblies were correctly seated into the chassis.
- I kept the suspension towers at their lowest settings for the initial installation, only raising the one suspension spring to level the platter.
- I tried rotating the spring assemblies to different positions but the spring opposite the motor opening is still the one that is more elongated.

My impression is that the weighting of the chassis is incorrect, rather than the adapter plate or spring being at fault. It’s based on my observation that the two suspension springs located on either side of the motor opening are extended fairly evenly and the spring opposite the opening is over-extended, indicating that the weight located at the motor opening is not heavy enough. It appears that additional chassis weight is needed under the motor opening ring to correctly balance out the weight of the tonearm and weight at the front of the chassis.

Anyone else experience this problem? Thoughts? Suggestions?


PS: I contacted Artech Electronics (US Distributor) and Michell Engineering to see what they say and will post their response when they get back to me.
The Arm , and plate together should weigh less
than 1 kg. Thats about the max an arm and plate can
weigh by design . It would appear to me , the balance
weight applied under the table is not too light
but rather you have too nuch weight on the arm side.

They all have the same balance weight applied. Weigh your arm and plate including bolts and see what it totals.

I have an Orbe SE with a Graham 2.2 TC with SME mount, I also owed a gyro SE mk II with an SME iv. You may need
a lighter plate made from acrylic.

Something else to check , is that your phono cable
is not adding a consciderable pulling downward force
that easily will throw the balance out .

Another thing to make sure of is that your
phono cable is not weighing or pulling the arm
down acting as added weight and restricting
bounce of the suspension.

Thanks for the reply; the suggestions you provide are things that I have considered, but I haven't had time to disassemble the tonearm and plate to compare its weight to the motor ring weight. I hope to do that this weekend.

I've been careful to be sure the tonearm cabling is not exerting force on the chassis.

I've spent some time looking at the configuration of the weights and how they are attached to the chassis. I may do some modifications to accomodate adjustments in the number and placement of the weights to allow fine-tuning to balance out the chassis. But only after checking the tonearm mounting adapter plate; it should be the corret one for the SME 309 since I ordered from an authorized Michell Engineering and SME retailer. But you never know. :-)

Solution was to buy a lightweight tonearm mounting plate...

Problem solved: Success! Lightweight acrylic plate.