ok, power supply question, 230v - 117v conversion - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

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 20th July 2009, 01:31 AM   #1
diyAudio Member
 
aardvarkash10's Avatar
 
Join Date: Mar 2007
Location: Auckland, NZ
Default ok, power supply question, 230v - 117v conversion

As I posted earlier, I havre bought four Rowe-AMI stereo jukebox amps. You should have seen the look on the cook's face...

Anyway, these are all ex-USA units and the power transformer is a 117VAC primary side unit. We are 230VAC in NZ. THe PTX is a beautiful lump with a centre-tapped HV, a 5V, and 2 x 6.3V windings. It looks like it could happly power the Ginza district.

Being a cheap and cheerful type, this has me more than a little upset. I could 1) replace the entire transformer - expensive, hard to source, and wasteful 2) have the transformer rewound - expensive and wasteful 3) run a 230VAC/117VAC transformer in front - expensive, ugly, more crap hanging around the AC outlet.

Then I thought about how to manage the 230VAC such that the transformer only sees 117VAC.

So, how about I half-wave rectify the 230VAC and feed that to the existing PTX?

Comments?
__________________
"Folks, you can't prove truthiness with information. You prove truthiness with more truthiness. In a process known as truthinessiness." - Stephen Colbert, The Colbert Report
  Reply With Quote
Old 20th July 2009, 03:54 AM   #2
diyAudio Member
 
Join Date: Apr 2003
Location: Portland,Oregon
Blog Entries: 4
Send a message via AIM to DigitalJunkie
Quote:
So, how about I half-wave rectify the 230VAC and feed that to the existing PTX?
Nope. Transformers don't like (and won't work on) DC. Rectifying AC = DC.
With a half-wave rect. you'd end up with a half of a sine wave,and a DC component,and the transformers would not be happy at all.
  Reply With Quote
Old 20th July 2009, 04:46 AM   #3
diyAudio Member
 
aardvarkash10's Avatar
 
Join Date: Mar 2007
Location: Auckland, NZ
Default I realise true DC is no good

but if you consider a half-wave rectified AC sine input, it is effectively a pulse transformer with a series of positive (or negative) pulses applied to the primary.

The only "DC" component (if you can call it that) is the period when the rectifier is not conducting, so there is no current. Would that still lead to core saturation?
__________________
"Folks, you can't prove truthiness with information. You prove truthiness with more truthiness. In a process known as truthinessiness." - Stephen Colbert, The Colbert Report
  Reply With Quote
Old 20th July 2009, 04:55 AM   #4
diyAudio Member
 
boywonder's Avatar
 
Join Date: Jan 2008
Location: So.Cal.
If you were going to operate them 2 at a time, you could wire the primaries for two of the amps in series........just trying to think outside the box.
  Reply With Quote
Old 20th July 2009, 06:08 AM   #5
diyAudio Member
 
aardvarkash10's Avatar
 
Join Date: Mar 2007
Location: Auckland, NZ
Default good thinking b-dubya!

of course, then I have to build it as a HT sysyem and that means building three more speakers and all that... Hey - grreat idea!
__________________
"Folks, you can't prove truthiness with information. You prove truthiness with more truthiness. In a process known as truthinessiness." - Stephen Colbert, The Colbert Report
  Reply With Quote
Old 21st July 2009, 12:27 PM   #6
diyAudio Member
 
Join Date: Aug 2008
I do all the electronic work for a guy who repairs, restores and imports juke-boxes to the UK. If there are no tappings on the main transformers I always fit a 230-115V transformer in the base of the box [there is always plenty of space]; it is the most safe thing to do. Don't forget to connect an earth [ground] lead to the metal chassis of the box.

Another issue you may have is that some boxes use a 60Hz a.c. motor to drive the turntable so the record will run at the wrong speed at 50Hz.
  Reply With Quote
Old 21st July 2009, 01:11 PM   #7
Merlinb is offline Merlinb  United Kingdom
diyAudio Member
 
Merlinb's Avatar
 
Join Date: May 2006
Location: Lancashire
Quote:
Originally posted by boywonder
If you were going to operate them 2 at a time, you could wire the primaries for two of the amps in series........just trying to think outside the box.
If the transformers are identical, it should be possible to run the primaries in series by the secondaries in parallel, yes? Observing correct phasing of course. More iron yes, but potentially one really powerful amp?
  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
Power Transformer 110/230V Windings Question LinuksGuru Tubes / Valves 4 13th July 2009 10:26 PM
velodyne dd12 117V->230V rabou2004 Subwoofers 2 29th June 2009 09:22 PM
Rotel RMB1048 110V 230V conversion tomekajja@yahoo Solid State 5 4th March 2008 10:06 PM
120V QSC PLX 230v conversion??? bOOgy77 Class D 1 5th December 2004 07:25 PM


New To Site? Need Help?

All times are GMT. The time now is 04:38 PM.


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