Redpoint Motor Controller


I seem to have developed a speed drifting issue, I can not seem to get it right. I have changed the bearing oil installed a new belt but, still have a speed drift over time. When I first turn on the TT the speed is fast for the first five minutes or so, then it settles down and is good for an hours or so. Then all of a sudden it is running slow, today after 2.5 hours of constant running it was running fast when I checked it. I am at a lost for what's causing this, I am sure it is the controller but what can go cause this when all else seems to be working?
jsman
The Redpoint uses a brushed DC motor.  They all drift.  Since the controller is open-loop - meaning there is no feedback from the platter (using a tachometer type device to send corrections to the controller), the speed will invariably drift due to stylus drag, thermal changes in the controller components and the motor itself.

I've been down this road, and have tried various open and closed-loop DC and AC controllers (Mark Kelly designs), as well as offerings from  Origin Live and Walker.  All are compromises - brushed DC motors are very difficult to control, and AC motors introduce the issue of cogging and vibration transmission.

Your best bet would be to implement a different controller architecture altogether.  Talk to Thom at Galibier Design.  His latest controller is a brushless, electronically commutated design, with hall-effect sensors around the motor spindle itself sending instantaneous feedback to the controller electronics.  It is one of the most significant upgrades I've ever made to my Galibier, and Thom should be able to help you out.  
Palasr,
Thank you for this information this is best description and info anyone has ever given me. So tell me what did you do for your Galibier? This has become so tiresome I can't stand it.

Jay
I think my last paragraph sums up what I've done - this (so far) is the best option I've found.  My second choice would be an open-loop AC controller capable of driving a 7W, 600 RPM AC motor, preferably a Premotec or Airpax/Phillips - lots of heavy lifting involved with my second choice. 

Contact Thom.  You'll be pleased.  
Hi Palasr,
I spoke with Thom the cost of a complete motor is more than I am willing to spring for. Gonna look at a few other options, maybe Thom and I can work something out he is more than willing to help it seems.

J
How much was the motor from Galibier?

You can build your own 3 phase BLDC controller for ~$100.  A compatible motor is ~$60.

http://www.diyaudio.com/forums/analogue-source/307918-3-phase-class-amp-diy-bldc-motor-drive.html
That's for sure a possibility, thanks for the link..