Fairchild 412 (or other Papst Aussenlaufer) Motor Controller

[watt]

Been getting reacquainted with the turntable below after Wardsweb worked his magic (thread here). I'm thoroughly enjoying it with the Roksan Nima and Rega RB-something that I have on there now. And I found an OMA graphite mat in my closet that works pretty nicely with the paperstone plinth. Tons of drive and authority, but it's also pretty quiet.

The point of this thread, though, is to investigate potential motor controllers that I could use with this table. Its motor is a Papst Aussenlaufer, which AFAIK appears on some other decks as well. As it stands, this particular Fairchild--a 412-2--runs at one speed. The majority of my record collection is 33 1/3, but I'd like the flexibility of playing 45, at least, and possibly 78 rpm.

Has anyone out there experimented with a motor controller for their 412 (or another turntable that uses a Papst)? I do know that Fairchild sold a model with a tube-based electronic drive unit, and the schematic for it is out there. But I also wonder if anyone has investigated other options, even some of the off-the-shelf speed controllers. I'm not that familiar with what's out there--been listening more and reading/buying less over the past few years.

I welcome any advice or comments. Thanks!

 

[Pio1980]

If member Bill Carlin of Phoenix Engineering was still active, he could talk the technical factors involved.
Basically, afaik these things don't "like" being run too far outside their design parameters range.

 

[watt]

If member Bill Carlin of Phoenix Engineering was still active, he could talk the technical factors involved.
Basically, afaik these things don't "like" being run too far outside their design parameters range.

I've seen some of the Phoenix products. Didn't realize that he once posted here.

About the design parameters, I wonder if that might be an argument for building one of the Fairchild ED controllers (or attempting to).

 

[Pio1980]

The PE ''Eagle" was the higher power controller for Thorens 124 and the like. Dunno if it had enough power for the Pabst, it iirc didn't do 78.

 

[bob smog]

Over the last 10-15 years, I recall several attempts, both tube and solid state, to create or recreate electronic drives for the 412.

Not an easy nut to crack, and certainly not cheap. Lots of good efforts, but ultimately abandoned.

It's a great table, enjoy it in all its single-speed glory.

(Disclaimer: I own 3 1/2 412s)

 

[Pio1980]

Basically, a stable variable frequency source into a power amplifier matched to the average load characteristics of the motor, which varies with the frequency. For motors with a capacitor, the capacitance should also be shifted.