Anti skating SME V

Normally I rather laugh at people who re-awaken zombie threads, but this was the first hit on a search for "SME V IV anti-skate"! I searched because I have been finding it awkward to set the anti-skate of late, so to be a bit more scientific about it I used a smooth grooveless record. I know, anti-skate counteracts skating force, and a grooveless record is not going to show the full stylus-groove interaction. For the sake of argument, let us agree it gets you in the ballpark (even the nine different ways of setting anti-skate tested by the maker of the Parks Puffin in a YT video showed the grooveless record as getting very close to all the other methods).

Now the grooveless record showed two SME IVs and an SME V still let the stylus wander slowly towards the centre even with the anti-skate set to the maximum of 3. The fourth arm, an SME M10 (call it a 309 with a cheaper sliding mount), can hold its position mid-disk with the anti-skate set to 2.5. This makes me think the first three arms have their anti-skate spring weakened by age, and perhaps should make a visit to West Sussex to have the spring replaced. But spending £1k per arm for a 10¢ spring seems extravagant. I shall ask my contact at SME if such a spring can be bought and fitted at home.

Question for the smart people here: I am right, am I not, in assuming the anti-skate on these arms is spring-loaded and not magnetic?

Got a reply from SME:

Dear Chris,

Thank you for your email to Elaine.

The anti skate spring can only be fitted / calibrated here at the factory due to unique tooling and measurement equipment used.

If you would like to send the arms for checking we would be happy to help.

Whilst writing we should mention that blank test discs are not recommended or suggested by SME due to inconsistent results leading to poor set up.
Best regards,
Brian

Decided to do it properly and ordered a Wally Skater....

I'd love to see how they calibrate a new spring.

Per ordering the Wally Skater, do what properly?  Set antiskate? With that response from SME, I think it adds weight to the idea not to use a blank LP to set AS.  And yet, the posts on doing it that way will keep on coming.

These SME arms have the usual set-up for spring-loaded anti-skate: turn a dial until it is set to a number corresponding to the VTF in grams. My issue is that doing this appears to be inaccurate—the stylus touches down and skates inwards into the middle of the first track. If I increase the anti-skate setting to a higher value it does not do this. But if I set it too high the stylus starts to mistrack about the middle of the record, by skipping back and refusing to go onwards. Turn the anti-skate down a little and it continues to play.* There is a happy medium where there is enough anti-skate at the start of a side, but not so much that it refuses to play right through the side. This seems to be a little higher than the expected value on the anti-skate dial. If I use a grooveless disk, I tend to get it set too high and I end up with mid-side mistracking. If I follow Peter Ledermann's method, I am setting the anti-skate just a little low for the run-out area in the hope it will be just right in the middle of the disk. Having just one ear and no ability to hear stereo I cannot  look for distortion in one channel or the other. So, yes, I am hoping to use the Wally Skater to get it set correctly. No doubt for each arm/cartridge combination there will be a correct spot in the suggested 9-11% of VTF it aims for, and I'll have to make a note for each one to save future experimentation. If it saves me one premature re-tipping it will have paid for itself. At the end of the day, I'll be happy to know I can set it simply so I find that happy medium where there are no issues at stylus touchdown or at mid-side.

*I have made sure the platter, tonearm panel and headshell are all horizontal.

@dogberry what you're describing suggests to me that the problem is more likely in the arm's bearings or wiring than in the antiskate mechanism.