Grounding a vintage amplifier - 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 4th January 2013, 02:28 PM   #1
diyAudio Member
 
Karl vd Berg's Avatar
 
Join Date: Jul 2012
Location: South side of the Sky
Default Grounding a vintage amplifier

Hi folks,

Maybe this was already discussed, but I couldn't find the proper place.

I'd like to ask if can change safely my Sansui AU-317's power cord to a more robust grounded one.

The "original" (2nd picture) is not that robust anymore and I'm afraid it will break in the case sometime.

I want to put a 250V 10A with the yellow wire (1st picture) and ground it at the amp's chassis.

Is there anything I have to avoid with the AU-317??
Attached Images
File Type: jpg P1040276.jpg (344.7 KB, 165 views)
File Type: jpg P1040277.jpg (341.8 KB, 154 views)
  Reply With Quote
Old 4th January 2013, 04:38 PM   #2
jaycee is offline jaycee  United Kingdom
diyAudio Member
 
Join Date: Apr 2004
Location: Norwich, UK
Make sure the signal ground is not connected to the chassis, otherwise you will probably get hum. Simply measure for conductivity between the case and the outer edge of one of the signal input sockets.

If there is a connection, you are best leaving the safety ground disconnected, but you can still fit an IEC socket which would allow you to use an IEC cable.
  Reply With Quote
Old 4th January 2013, 05:08 PM   #3
diyAudio Member
 
Karl vd Berg's Avatar
 
Join Date: Jul 2012
Location: South side of the Sky
Quote:
Originally Posted by jaycee View Post
Make sure the signal ground is not connected to the chassis, otherwise you will probably get hum. Simply measure for conductivity between the case and the outer edge of one of the signal input sockets.

If there is a connection, you are best leaving the safety ground disconnected, but you can still fit an IEC socket which would allow you to use an IEC cable.
Excellent! So, if there isn't any conductivity between the case and both of the input socket (with gear switched on), it's safe to ground in the chassis, right?

And remember the Rotel? I followed your instructions and put another transformer, did the Bias adjust (totally out of specs!) and now it's sounds really nice! The other transformer didn't have any thermal fuse inside, so I had to change the transformer!
  Reply With Quote
Old 5th January 2013, 12:41 AM   #4
jaycee is offline jaycee  United Kingdom
diyAudio Member
 
Join Date: Apr 2004
Location: Norwich, UK
You can test it while it's not switched on. Just use an ohm meter or so. A lot of Japanese amps did not have grounded cases.

Good news about the Rotel. They do have thermal fuses in the transformers but they are buried right inside the windings, so there's no chance of replacing them. Glad to hear the substitute works well. I have an RA-930 AX myself, a bit battered (the plastic base cracked and someone took out the rubber end cheeks) but it has a nice sound.
  Reply With Quote
Old 5th January 2013, 02:44 PM   #5
diyAudio Member
 
east electronics's Avatar
 
Join Date: Jan 2006
Location: Athens GREECE
Quote:
Originally Posted by Karl vd Berg View Post
Excellent! So, if there isn't any conductivity between the case and both of the input socket (with gear switched on), it's safe to ground in the chassis, right?

And remember the Rotel? I followed your instructions and put another transformer, did the Bias adjust (totally out of specs!) and now it's sounds really nice! The other transformer didn't have any thermal fuse inside, so I had to change the transformer!

(totally out of specs!)

expected ...wonder why ? i think there is a bias stabilizer cap that goes bad ....if you also talk about the stupid yellow capacitor in the feedback of 100ufd/6.3 Volt is also joke quality and specs

it will be much better to replace those ...
__________________
SERVICE ΕΝΙΣΧΥΤΩΝ ΚΑΙ ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr
  Reply With Quote
Old 6th January 2013, 03:22 AM   #6
diyAudio Member
 
Karl vd Berg's Avatar
 
Join Date: Jul 2012
Location: South side of the Sky
Quote:
Originally Posted by sakis View Post
(totally out of specs!)

expected ...wonder why ? i think there is a bias stabilizer cap that goes bad ....if you also talk about the stupid yellow capacitor in the feedback of 100ufd/6.3 Volt is also joke quality and specs

it will be much better to replace those ...
Hello Sakis!

Yes! the bias was out a lot! Has to be 4mV and the right chnl. was 5.8mV, while the left chnl. was 38mV!

You might be right. Do you mean those tiny yellow/orange caps near the input source?? They are the only ones in that color, the others are Black Gate (the amp is from 1994 though!)

If those yellow are behind the bias stabilizer, I can put some Panasonics FC I still have...
Attached Images
File Type: jpg rotel_ra930bx.jpg (269.8 KB, 70 views)
File Type: jpg rotel_ra930bx_bg.jpg (139.2 KB, 66 views)

Last edited by Karl vd Berg; 6th January 2013 at 03:26 AM.
  Reply With Quote
Old 6th January 2013, 12:57 PM   #7
diyAudio Member
 
east electronics's Avatar
 
Join Date: Jan 2006
Location: Athens GREECE
from 4 to 5.8 is no problem but 38 might be it seems that your amplifier doesnt use this typos of caps so you might as well be ok

the cap can be seen as the last cap to see in your phono stage right middle top side of your picture ...usually these are the caps that go bad ...

your version seems upgraded so nothing to be bothered
__________________
SERVICE ΕΝΙΣΧΥΤΩΝ ΚΑΙ ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr
  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
Amplifier grounding Kay Pirinha Instruments and Amps 6 6th June 2012 04:44 AM
Pre-amplifier grounding compendium? gentlevoice Solid State 14 26th April 2012 08:15 AM
Grounding problem of my OTL headphone amplifier ronardi Headphone Systems 1 17th May 2006 04:19 PM
pre/amplifier grounding Alkis Tubes / Valves 4 27th February 2005 07:56 PM
Grounding your amplifier? thylantyr Solid State 3 30th April 2003 07:04 AM


New To Site? Need Help?

All times are GMT. The time now is 07:26 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