amp 120v-240v conversion - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 October 2003, 02:29 PM   #1
chrish is offline chrish  Australia
diyAudio Member
 
chrish's Avatar
 
Join Date: Oct 2003
Location: Sydney
Default amp 120v-240v conversion

Hello all,

Am new to the forums and have a limited knowledge of electronics so have a question that someone may be able to help with...

I have a circa 1990 Adcom GFA-555 power amp that was purchased in the USA, so runs on 120 volts. I live in Australia which has 240 volts. I am running this amp from an external step down transformer, but am interested in seeing if I can convert it to run on 240 volts and do away with the external transformer. I was hoping there may be a way to re wire the taps from the power supply torroid that would not involve too much re-working of the amp. The wires from the primary of the torroid are as follows:

Blue ------- 120 vac \
Joined - connected to power cable
Black--------120 vac/


Yellow---------------\
Joined
White---------------/


Brown------120 vac - through power switch and fuse

Orange - not used
Red - not used

Would appreciate if anyone could offer some advice / help.

Thanks guys,

Chris
  Reply With Quote
Old 20th October 2003, 03:28 PM   #2
sam9 is offline sam9  United States
diyAudio Member
 
sam9's Avatar
 
Join Date: Jun 2002
Location: Left Coast
The best approach is to contact Adcom and ask them. The description sounds like the transformer can be wired for different mains.

Without info from Adcom, it could probably be done but since you are dealing with main (240v yet!) I recommend this be done by a local tech with more experience wiyh the local power mains than you indicate you have. For one thing, there are so many ways transformers are built (and no standardization on colors - at least that I would trust), that the only sure and safe approach is to 6take some resistance measuresments on the primary side, make an educated deduction, then carefully apply power and measure what comes out the secondary. After that different fusing is required and posibly a different power switch.



Likely it is easy if done right but a potential disaster (not just to the equipment) if done incorrectly.
  Reply With Quote
Old 20th October 2003, 04:53 PM   #3
diyAudio Member
 
mrfeedback's Avatar
 
Join Date: Feb 2002
Location: Perth, Australia.
Default Mains Polarity can Be Strongly Important..........

Provided that your extenal step down transformer is generously rated, I find that the mains isolation provided by this external transformer can be sonically a very good thing.
If you want to go the last mile, fit a mains polarity reversing switch at the input connection and the output socket of your external transformer box.
This will give you 4 switch permutations to try, and because of earth leakage in unbalanced systems, expect mains input and output polarity changes to affect/effect sonics.
Further swapping the mains polarity into the CDP with will give you another 4 polarity combinations to try - if you have a CDP fig-8 mains cable this is easy.

Be sure to consult your electrical expert about fitting polarity reversal switches where appropriate if you are not completely clear on this.

Eric.
__________________
I believe not to believe in any fixed belief system.
  Reply With Quote
Old 20th October 2003, 08:40 PM   #4
diyAudio Member
 
georgehifi's Avatar
 
Join Date: Sep 2003
Location: Manly Australia (Jewel of the Pacific)
Send a message via MSN to georgehifi
Chrish, i`m also in Australia and am currently trying to get my Adcom gfa-585 up and running, it`s got some problems, but on the inside of the front pannel Adcom sticks a label with instuctions on how to wire for 100,120v,200,or 240v, It`s all rewirable on the big terminal block on the relay soft start board. Have a look you may be pleased.
__________________
Avatar : Production Lightspeed Attenuator
www.lightspeedattenuator.com
  Reply With Quote
Old 20th October 2003, 10:09 PM   #5
chrish is offline chrish  Australia
diyAudio Member
 
chrish's Avatar
 
Join Date: Oct 2003
Location: Sydney
Thanks for all the replies.

Have sent an email to Adcom, lets see what happens on that front...

Georgehifi, unfortunately no sticker describing re-wiring...
  Reply With Quote
Old 21st October 2003, 12:46 PM   #6
AJT is offline AJT  Philippines
diyAudio Moderator
 
AJT's Avatar
 
Join Date: May 2003
Location: Palatiw, Pasig City
Default check the red and orange wires

you can find out with a dmm set to read ohms if these wires connect to any other wires, wether i connect to primary or secondary windings if at all, you can also measure any ac voltage present in these wires, then we shal know...be very carefull though...
  Reply With Quote
Old 21st October 2003, 09:02 PM   #7
diyAudio Member
 
georgehifi's Avatar
 
Join Date: Sep 2003
Location: Manly Australia (Jewel of the Pacific)
Send a message via MSN to georgehifi
Chris ,ok i`ll give you my GFA-585 wiring block layout maybe it`s the same.
The block has 9 entry points
As it`s wired in mine for 240v i have 1=yellow 2=orange 3=n/c 4=blue 5=black 6=n/c 7=red 8=n/c 9=white.

Black Red and White remain constant in 5,7,and 9 regardless of what voltage you want, only yellow ,orange and blue get moved around for the different voltages.


ps this is about as clear and safe as i can explain it, if it`s the same all should fall into place with no questions.

Cheers George
__________________
Avatar : Production Lightspeed Attenuator
www.lightspeedattenuator.com
  Reply With Quote
Old 6th December 2004, 10:07 AM   #8
stu.dio is offline stu.dio  Greece
diyAudio Member
 
Join Date: Dec 2004
Location: Athens
If have the GFA 555 aswell, and need to source the wiring layout so I can convert the 120v to 240 - did you manage with yours a yr ago? do you know this post is actually here? I wait in hope that you do. Pls feel free to email me.
I also have a conrad johnson PV-5 preamp that needs the same treatment - anybody tried this? - I can say to anyone who hasn't seen inside one of these - it's beautiful... they don't make them like this anymore (etc..) wish I knew a bit more to do it myself.
  Reply With Quote
Old 12th December 2004, 08:27 AM   #9
chrish is offline chrish  Australia
diyAudio Member
 
chrish's Avatar
 
Join Date: Oct 2003
Location: Sydney
I ended up purchasing a copy of the 555 service manual from a vendor on Ebay. The last page of the manual has a diagram showing how to configure for various voltages. I will attach an image of that page. Hope this helps.

Chris
Attached Images
File Type: jpg gfa555.jpg (59.9 KB, 164 views)
  Reply With Quote
Old 12th December 2004, 09:31 AM   #10
Eva is offline Eva  Spain
diyAudio Member
 
Eva's Avatar
 
Join Date: Oct 2003
Location: Near the sea
Send a message via MSN to Eva
TIP : Connect a 100W light bulb in series with the mains supply when first powering up the amplifier after changing voltage configuration. Results will be much less harmful in case of a wiring mistake
  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
120v/240v amplifiers dsiroky Solid State 1 25th September 2008 11:58 AM
Spacedeck 240V to 120V lt_texan Analogue Source 3 10th December 2007 02:41 AM
Two 120V transformers in series for 240V ? Bernhard Power Supplies 8 22nd November 2005 12:28 AM
120v to 240v conversion for Pioneer vsx-D912 dg2176 Power Supplies 1 10th April 2005 05:24 PM
toroid rewiring from 240v to 120v pjb Parts 3 22nd February 2004 01:28 PM


New To Site? Need Help?

All times are GMT. The time now is 09:53 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