Decca DPS8: Motor Issue? - 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 4th September 2013, 03:25 AM   #1
slor is offline slor  United States
diyAudio Member
 
Join Date: Jul 2007
Default Decca DPS8: Motor Issue?

I've been restoring a mid-50s Decca DPS8 turntable for a friend, and I'll be damned if this isn't one of the most frustrating jobs I've taken on.

Every relevant component (electrolytics, tubes, speaker) has been replaced, the motor disassembled and relubed, motor mounts replaced. But speed is erratic, and the motor runs very hot.

I saw that the motor was rated "90V, 60Hz" and as an experiment, I subbed in an identical motor (but rated 117V).

Still runs hot, and eventually erratically.

I'm going to try dropping resistors on the motor circuit, but it's a bit of a shot in the dark. Does anyone with an education have a better suggestion?

Many thanks,
Seth
  Reply With Quote
Old 5th September 2013, 12:05 AM   #2
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Does it run hot out of the turntable? What sort of motor is it? Synchronous or shaded pole induction with provisions for variable speed (adjustable)

Are you sure the table is up to snuff mechanically?

This would probably be better off in analog source so I will move it there.
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 5th September 2013, 12:13 AM   #3
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Should you come up empty here try Vinyl Engine | The Home of the Turntable - you have to be a member.
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 5th September 2013, 12:40 AM   #4
slor is offline slor  United States
diyAudio Member
 
Join Date: Jul 2007
I believe it is a synchronous motor; speed change is effected by altering the position of the idler wheel against the stepped capstan.

After further testing, I found that both motors run quite hot outside the turntable (both run off a variac at correct voltage, and removed from the mounting plate so as to remove that as a culprit).

So I'm going on the assumption that both are, to put it unscientifically, fried. I'm sad, as the 117V motor was a spare, and I believe was strong. For that matter, the 90V motor seemed strong when I first serviced the turntable. I can't think of anything that I did to change this, but evidence suggests otherwise.

Sadly, at this point, I think the turntable is junk.

Many thanks,
Seth
  Reply With Quote
Old 5th September 2013, 08:56 PM   #5
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
One last shot, and service the motor bearings as explained in the TD124 thread. Check alignment as well. See if motor runs hot when everything not tightly bolted together.
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 5th September 2013, 09:56 PM   #6
diyAudio Member
 
Join Date: Dec 2012
Location: The Jurassic Coast, England. GB
Send a message via Skype™ to JonSnell Electronic
When the motor is out of the chassis, can you spin it without any friction?
__________________
www.flyingmole.co.uk For World Wide support for Flying Mole, Class D, Refurbishment and Repairs. www.jonsnell.co.uk
  Reply With Quote
Old 6th September 2013, 02:06 AM   #7
slor is offline slor  United States
diyAudio Member
 
Join Date: Jul 2007
Yes, the motors (both the 90V and 117V models) spin fine. But after 10 - 15 minutes powered up, they are both very hot.

When I disassembled them initially, I cleaned the shafts with a clean rag, then poured a few drops of sewing machine oil into the felt surrounding the plain bronze bearings.

Kevin, thanks for the pointer. I am poring through that very long, but very informative thread now!
  Reply With Quote
Old 6th September 2013, 03:33 PM   #8
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Are they plain bronze or sintered? In any event either way all old lubricant should be removed.

Can you post a few pictures of these motors? Trying to figure out if the rotor is at the root of the issue.
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  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
Decca Blue barclay136 Analogue Source 10 1st April 2013 07:58 AM
Decca Portable Record Player model DPS8 Filter cap replacment starblazer123 Tubes / Valves 34 10th November 2012 03:33 AM
Lambda motor vs. XBL^2 motor vs. any other motor Thinkcat Subwoofers 16 23rd December 2008 06:23 AM
Decca FFSS DavidSC Analogue Source 11 17th December 2006 06:23 PM
DECCA unipivot tonearm Merijn Analogue Source 19 3rd February 2003 11:07 AM


New To Site? Need Help?

All times are GMT. The time now is 03:20 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