Go Back   Home > Forums > >

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

AC motor drive from single-ended supply
AC motor drive from single-ended supply
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
Old 26th February 2021, 08:54 AM   #1
Airprodigy is offline Airprodigy  United Kingdom
diyAudio Member
 
Join Date: Jan 2018
Default AC motor drive from single-ended supply

Can anyone explain this to me? It's probably a really dumb question!

The schematic shows the motor drive for the Thorens TD320 turntable. the motor is 16V AC. The power supply is single ended 18V.

My question is this. The supply to the motor needs to be as in diag A, so going from + to - does it not? But if the power supply is +18V the supply to the motor will be like in diag B. In which case, how does that run the motor?
Attached Images
File Type: jpg IMG_20210226_092234.jpg (237.2 KB, 102 views)
File Type: jpg Thorens TD300 series service manual-page-011.jpg (257.6 KB, 96 views)
  Reply With Quote
Old 26th February 2021, 09:17 AM   #2
JonSnell Electronic is offline JonSnell Electronic  United Kingdom
diyAudio Member
 
JonSnell Electronic's Avatar
 
Join Date: Dec 2012
Location: The Jurassic Coast, England. GB
The motor is a 3 phase motor and gets power from Z101. The first part controls the oscillator speed where the three other op amps control the three phases. Phase offset is acheived by RC timing from the oscillator.
__________________
Support for Fender, Marshall and all Valve Equipment; Audio Innovations, Audiorama FU29, Quad and Leak. www.jonsnell.co.uk
  Reply With Quote
Old 26th February 2021, 09:22 AM   #3
Airprodigy is offline Airprodigy  United Kingdom
diyAudio Member
 
Join Date: Jan 2018
Thanks for your reply.
It's a 2-phase motor, I believe.
I'm wondering not about phase but how the AC output swings from + to - if the power supply is +18V.
  Reply With Quote
Old 26th February 2021, 09:36 AM   #4
msdin is offline msdin  United Kingdom
diyAudio Member
 
Join Date: Sep 2006
The drive board for the TD320 is a Quadrature oscillator with a zener agc which then feeds 2 H-bridge amplifiers to supply the 2 motor windings.
The transistors in the H-bridge are TO92 packages. R110 and R119 bias the opamp.

This is similar to the Phonosophie No.3

motor and circuit for diy turntable project

Last edited by msdin; 26th February 2021 at 09:43 AM.
  Reply With Quote
Old 26th February 2021, 09:41 AM   #5
richb is offline richb  United Kingdom
diyAudio Member
 
Join Date: Feb 2012
Location: Southampton
Your picture A assumes one side of a motor winding is grounded. However this circuit drives both sides of each motor winding in the range 0->18v, so we can have the case where:
- side_A = 17v, side_B = 1v => voltage AB = 17-1 = +16v
- side_A = 1v, side_B = 17v => voltage AB = 1-17 = -16v
Hope that helps!
  Reply With Quote
Old 26th February 2021, 10:00 AM   #6
Airprodigy is offline Airprodigy  United Kingdom
diyAudio Member
 
Join Date: Jan 2018
Ah! richb yes that does make sense now.
Much appreciated!
  Reply With Quote
Old 26th February 2021, 11:26 AM   #7
Arch Stanton is offline Arch Stanton  France
diyAudio Member
 
Arch Stanton's Avatar
 
Join Date: Mar 2012
It seems to be the PS800, I have one from a TD850, it is not very accurate in frequency nor stable.
  Reply With Quote
Old 26th February 2021, 01:32 PM   #8
Airprodigy is offline Airprodigy  United Kingdom
diyAudio Member
 
Join Date: Jan 2018
Oh really? I've had several TD300 series over the years and I've found the speeds very stable. I currently run a TD520 which has a built-in strobe and the speeds are solid as a rock. It has essentially the same drive circuit as the 300 series.
  Reply With Quote
Old 26th February 2021, 02:33 PM   #9
Mark Tillotson is offline Mark Tillotson
diyAudio Member
 
Join Date: May 2018
Location: Cambridge UK
Its an RC oscillator at heart, so definitely nothing like as stable as ac mains or a quartz-derived signal, doesn't mean its not good for the job though.
  Reply With Quote
Old 26th February 2021, 07:08 PM   #10
Airprodigy is offline Airprodigy  United Kingdom
diyAudio Member
 
Join Date: Jan 2018
Quote:
Originally Posted by msdin View Post
The drive board for the TD320 is a Quadrature oscillator with a zener agc which then feeds 2 H-bridge amplifiers to supply the 2 motor windings.
The transistors in the H-bridge are TO92 packages. R110 and R119 bias the opamp.

This is similar to the Phonosophie No.3

motor and circuit for diy turntable project
I realise the circuit contains an RC oscillator . However I am a bit puzzled - it seems to most closely resemble a quadrature oscillator using the two top left op amps. However a quadrature oscillator requires 3 RC segments whereas this only appears to have 2 ( consisting of the 1% toleranced caps and resistors, I assume). I'm obviously missing something here!
  Reply With Quote

Reply


AC motor drive from single-ended supplyHide this!Advertise here!
Thread Tools

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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
"Balanced" vs single ended headphone drive chris719 Headphone Systems 11 14th September 2012 06:45 PM
Lambda motor vs. XBL^2 motor vs. any other motor Thinkcat Subwoofers 16 23rd December 2008 06:23 AM
Single Ended, Single driver: In-room distortion measurements Gerrit Boers Full Range 4 27th November 2007 08:12 AM
Anyone play with the Zen Single-Stage Single-Ended Class A? Rino odorico Pass Labs 13 29th August 2002 09:01 AM


New To Site? Need Help?

All times are GMT. The time now is 04:18 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
Copyright ©1999-2021 diyAudio
Wiki