how to add 78 RPM and/or variable speed pot to DD turntable motor?? - diyAudio
Go Back   Home > Forums > Source & Line > Analogue Source
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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
Thread Tools Search this Thread
Old 8th February 2010, 11:19 PM   #1
diyAudio Member
Join Date: Feb 2010
Question how to add 78 RPM and/or variable speed pot to DD turntable motor??

I'm making a dreamachine and need a 78RPM turntable....don't have one and would like to add 78 RPM to my old DD sony that I tore apart (33 and 45 RPM). I'd love to make it spin at 78RPM and if possible make it adjustable with a pot up to maybe 90 or 120 RPM

When I hit the speed select button I'm sure it switches between two different circuits. Is there just a resistor I can change or something and add a pot in there somewhere? ....I bet I would be able to figure it out on my own if it was belt drive.
  Reply With Quote
Old 9th February 2010, 07:28 AM   #2
diyAudio Member
Join Date: Sep 2009
Location: Central NY
Usually the speed switch changes the input frequency of a syncronous motor, thus changing the speed. Most have a feedback loop from a photo-tach and a fine adjust pot.

Lacking a circuit diagram, look over the speed switch circuit and fine adjust to see if it is indeed the resistance that sets the speed. If the speed switch changes fixed resistors, based on those 2 values you can calculate an approximate value to produce 78 rpm. Another option would be making a new tach wheel (usually opto-interupptor setup under the platter) for 78 and switching between opto-interupptors with a 4pdt switch.

All this assumes it'll go to 78 (motor controls/motor limitations) - experimentation will tell.

Why would you want to go to 120rpm? You'd need a laser to track at that speed. Disk brakes. And asprin. Lots of asprin.
Whatever it takes.
  Reply With Quote
Old 9th February 2010, 02:05 PM   #3
diyAudio Member
Join Date: Feb 2010
thanks. I'm making a dreamachine. it doesn't play records... it plays light!
  Reply With Quote


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
turntable motor & speed control space-cake Analogue Source 0 22nd September 2007 07:51 PM
Add-on for MM-RIAA to EQ 78 RPM records? DeonC Analogue Source 17 31st July 2007 09:54 PM
Modifying RIAA playback for 78 rpm/45rpm ashok Analogue Source 5 16th January 2007 10:23 PM
78 RPM recommendation anyone ? jackinnj Analogue Source 19 2nd February 2006 01:31 AM
When you don't have a 78 rpm turntable... Circlotron Analogue Source 7 24th November 2002 11:10 AM

New To Site? Need Help?

All times are GMT. The time now is 07:48 PM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2