Oracle motor/controller problems - DIY turntable - diyAudio
Go Back   Home > Forums > Source & Line > Analogue Source

Analogue Source Turntables, Tonearms, Cartridges, Phono Stages, Tuners, Tape Recorders, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 29th January 2008, 05:21 AM   #1
g-horn is offline g-horn  Canada
diyAudio Member
 
Join Date: Jul 2007
Default Oracle motor/controller problems - DIY turntable

I've built a turntable using the motor, controller, bearing and sub-platter from an
Oracle Alexandria table that had been scrapped because of frame problems.

I put the motor in a separate pod, mounted the control board into a box and
ran a (cassette tape) belt to the sub-platter. The motor is spinning WAY faster
than it is supposed to be and the buttons for 33, 45 and pitch don't seem to
have any effect. The motor also has a whining noise at speed which I don't
think should be there. I don't know if these pieces worked properly before I took
it apart. Any ideas on what I could do next?
Attached Images
File Type: jpg ormotocontr3.jpg (48.9 KB, 985 views)
  Reply With Quote
Old 29th January 2008, 07:21 AM   #2
Nanook is offline Nanook  Canada
diyAudio Member
 
Nanook's Avatar
 
Join Date: Feb 2004
Location: Chinook Country.Alberta
Default where's the rest of it?

The Alex has a two piece (as in two box) power supply, besides the internal electronics to switch speed (if it was an Alex Mkll). not sure if that helps. Someplace I have my manual....
__________________
stew -"A sane man in an insane world appears insane."
  Reply With Quote
Old 29th January 2008, 08:53 PM   #3
g-horn is offline g-horn  Canada
diyAudio Member
 
Join Date: Jul 2007
Default Piece Missing?

Hi Nanook
There weren't any other parts in the box related to the motor or supply. Is it a voltage stabilizer that I need? I can ask the guy that I got it from if he knows of its whereabouts.

Are there any work-arounds if it can't be found?
  Reply With Quote
Old 1st February 2008, 12:40 AM   #4
g-horn is offline g-horn  Canada
diyAudio Member
 
Join Date: Jul 2007
Default DIY turntable pictures

Thought i would post a couple of photos of the turntable without the motor and control box.
It has an air-bearing arm - Ladegaard style - using aluminum, wenge, carbon fibre, epoxy. Platter is acrylic, lathe turned. Plynth is solid padauk, wenge, aluminum, baltic birch ply sitting on wenge cones. The base has sand-filled 2.5 inch diameter aluminum tubes, a sandbox made of wenge, with a slab of Ubatuba granite.

Don't know how it sounds yet! Need help with the motor!
Attached Images
File Type: jpg gttpic0801sml.jpg (64.5 KB, 915 views)
  Reply With Quote
Old 1st February 2008, 12:41 AM   #5
g-horn is offline g-horn  Canada
diyAudio Member
 
Join Date: Jul 2007
Default DIY Turntable pictures

Another photo...
Attached Images
File Type: jpg gtt-armsml.jpg (61.9 KB, 860 views)
  Reply With Quote
Old 3rd February 2008, 12:15 AM   #6
Nanook is offline Nanook  Canada
diyAudio Member
 
Nanook's Avatar
 
Join Date: Feb 2004
Location: Chinook Country.Alberta
Default still looking for my manual....

but did you use the Oracle's inner platter?, gimme a pix if you did or didn't please if possible.

Great looking Ladegaard arm!

thanks

stew
__________________
stew -"A sane man in an insane world appears insane."
  Reply With Quote
Old 3rd February 2008, 12:30 AM   #7
g-horn is offline g-horn  Canada
diyAudio Member
 
Join Date: Jul 2007
Yes, the acrylic platter sits atop of the Oracle sub-platter. I had a machine shop with a CNC machine set the piece in. I've attached a drawing.

The control buttons won't even switch off the motor any more. Motor spins very fast.
Attached Files
File Type: pdf g_tt-4.pdf (64.6 KB, 183 views)
  Reply With Quote
Old 3rd February 2008, 03:25 AM   #8
Nanook is offline Nanook  Canada
diyAudio Member
 
Nanook's Avatar
 
Join Date: Feb 2004
Location: Chinook Country.Alberta
Default g-horn....don't even try to make it work...YET!

Let's have a look at the complete electrical system. It almost sounds (sorry for the pun, not intended) like the power supply is putting out AC, or it is being rectified as voltage *sqrt(AC voltage). DC motors get quicker when more voltage is applied. I'll stop right now, but will look directly for my manual and also try to get some voltage numbers off of my power supply and Dynamic Isolator.

OK here's the results of the voltages. Power supply outputs 33 VDC, the "Dynamic stabilizer" puts out 23.8 VDC (at least at my house, but I think the motor is a 24 VDC one actually). My guess is that when set to 33 1/3 rpm, your turntable is spinning at about 46 rpm. Sound about right?

so a couple of alternatives: Get a "Dynamic stabilizer" from whence your turntable parts came from, or build or get a rock stable 24 VDC power supply. Surplus shops may be able to help you out there (or 2 12V sealed gel batteries, and a trickle charger). Then give it a try. Do you have a strobe disc or other means for checking speed accuracy?


stew
__________________
stew -"A sane man in an insane world appears insane."
  Reply With Quote
Old 3rd February 2008, 04:39 PM   #9
g-horn is offline g-horn  Canada
diyAudio Member
 
Join Date: Jul 2007
Thanks for your help on this Nanook, much appreciated.

I measured 33 VDC as well at the power supply. I'm still waiting to hear back from the seller about the missing stabilizer. If it is unavailable, I guess I will try to source a 24 V power supply.

I printed out a strobe disc and a parts list for that DIY hand-held strobe but i haven't got around to making it yet.

Cheers,
Mal
  Reply With Quote
Old 15th February 2008, 03:25 AM   #10
g-horn is offline g-horn  Canada
diyAudio Member
 
Join Date: Jul 2007
I'm told that since the controller contains a LM317T regulator it doesn't require the Dynamic stabilizer box. I'm going to check my wiring again but apart from that, I'm in over my head.

What kind of power supply should I be looking for if I still can't make this work? Is there something off-the-shelf that could be recommended or does someone have a plan for a simple DIY project?

Any thoughts would be appreciated.
Cheers,
Mal
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
oracle alexandria turntable HELP! fortytwo Analogue Source 6 29th April 2009 09:50 PM
WTD - DC turntable motor + controller copydex Swap Meet 0 12th December 2008 08:54 PM
Improving a turntable (motor controller circuit) ;) sek Analogue Source 26 15th September 2008 09:44 AM
Oracle MKV motor details please frank2395 Analogue Source 0 15th August 2005 12:47 AM
Oracle Delphi motor can't achieve right speed... m.parigi Analogue Source 12 10th December 2003 07:49 PM


New To Site? Need Help?

All times are GMT. The time now is 04:50 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2