Need help with '63 Micromatic tonearm adjustment

I have a '63-64' Astro-Sonic with the curved black tonearm. The tonearm sometimes "slips" or "jerks" onto the first track too quickly in Auto mode. It seem to work better on records with multiple outer grooves. The needle is new. Is this something that can be adjusted? Thanks.

It's not a tone arm adjustment issue. It's all the things going on beneath. That idler wheel and all the crap attached to it. I hate to say "crap", but there's alot of stuff going on under there, and you need a Tech or someome knowledgeable about the nature of the beast that makes it work. That wheel that controls the change cycle and all its accompanying parts/linkages. I've encountered some Turntables where the arm would set down gently, but jerk violently inward with a vengance, scratching the damn record...LOL. Can't remember what the fix was, and I apologize for not being of any help at all.

Well, anyhoo, hoping all you folks have a blessed and prosperous New Year. A few blessings and prosperity never hurt anyone. I hate to sound like a worn out record, but I really enjoy and appreciate this board, and with the wonders of the Internet, we have been able to share alot with people around the world.

This is not a State of the Union address, but my heart and prayers go out to those who are still unemployed after all these years with our dysfunctional economy, and those working minimum wage just to make ends meet. I'm not living in the lap of luxury, but not exactly scraping, either, and do not take this Board for granted, and glad that I can share and receive the knowlege that's been bestowed here. You have no idea how much you all mean to me. --BB

Bobby Basham
Tucson, Arizona

It's the records.

It's called a groove guard, and is the reason Magnavox replaced the changer that can play odd sized records with changers that play only the 3 standard sizes.

They changed the design of the records, to the chagrin of the changer manufacturers. The record is thinner between the groove guard outer ridge and the label, so the grooves do not touch each other. Unfortunately, this causes havoc with older changers, because the stylus sets on the groove guard, rather than inside it. Gravity then causes the arm to slide inward, jumping the stylus into the music.

Newer changers have the 12" point set slightly farther in, but this can't be done on the changers that do odd sized records without also affecting the 7" set down point.

If you play few 7" records, you can change the setdown point adjustment with the screw in the hole in the plinth between the arm shaft and the turntable. Adjust it to land inside the groove guard.

I have been trying to design something to prevent this problem, but so far have not been completely successful.

One thing I did that helped some was to slow down the change cycle. This causes the arm to lower slower. I readjusted the change cycle idler height to engage the 33 step instead of the 45 step. I then adjusted the position of the motor assembly slightly so it would drive the cycle.

If this is happening on records without groove guards, then other effects could be occurring:

1. Skating, because the arm has overhang. Since this arm has no antiskating, the pickup drag could cause the stylus to move toward the spindle. It is worse with higher tracking forces.

2. A bent or loose locator leaf spring on the change cycle cam. This pinches the pickup arm positioning finger between the outer cam wall and the spring, so the setdown is consistent. If it is bent, it can flip the positioning finger to one side as the arm sets down.

Note: The locator spring affects 7" records too.

3. The arm height setscrews are misadjusted. There is a screw on top of the arm just above the arm shaft, and another screw at the right rear of the plinth. These need adjustment if the arm suddenly drops to the record at the end of the change cycle after lowering slower.

NOTE: If the record plays properly if it is higher in the stack, then the height adjustment is the trouble.

4. The pickup arm positioning finger is set too high off the cam face. This causes it to jump over the locator spring. The adjustment screw and nut are on the opposite side of the friction clutch from the positioning finger. Adjust for 1/32 inch between the finger and the cam face when the changer is out of cycle.

Note: The pickup positioning lever adjustment affects 7" records too.

5. Foreign matter on the cam face. There should be very little lubrication on it. Too much can drag the positioning finger to one side. It can also prevent the stylus from tracking the groove. I use graphite cylinder lock lube on mine.