Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Solid State Talk all about solid state amplification.

Why not ground everything straight to chassis?
Why not ground everything straight to chassis?
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 2017, 01:26 PM   #71
billshurv is offline billshurv  United Kingdom
diyAudio Member
 
billshurv's Avatar
 
Join Date: Mar 2014
Why not ground everything straight to chassis?
I would as I said make flying leads back to the miniDSP and see what happens. Work back up the chain one step at a time until the cause is found then fix that.
  Reply With Quote
Old 20th October 2017, 04:20 PM   #72
uzernaam is offline uzernaam  United States
diyAudio Member
 
uzernaam's Avatar
 
Join Date: Oct 2010
Location: Phoenix Arizona USA
If you look closely at the black wires soldered to the shield tabs, you can see strands of the ground wire running right next to them soldered to the same point.

I did this per tomchr's instructions here:
Attached Images
File Type: jpg rcashield.jpg (270.2 KB, 58 views)
  Reply With Quote
Old 20th October 2017, 04:37 PM   #73
tom2016 is offline tom2016
diyAudio Member
 
Join Date: Feb 2016
If this were my board, I would try two things:

1) Place 1K resistors in series with both the plus and minus inputs at the modulus input connector. See if hum decreases/disappears.

2) if that doesn't work, then try this: Connect the black wire and shield AND one leg of a 100K resistor to the minus input and the other leg of the resistor to the ground input on the modulus input connector.

Both of these approaches are trying to isolate the negative input of the differential amplifier from the ground loop issues. One of them hopefully will work for you.
  Reply With Quote
Old 20th October 2017, 04:42 PM   #74
Chris888 is offline Chris888  United Kingdom
diyAudio Member
 
Join Date: Sep 2017
Location: Cornwall UK
IS the shield connection at J2 ground on the PCB?
There is a big old ground loop mains > box > PCB > J2 > shield > box?
Does the transformer have a screen connection?
  Reply With Quote
Old 20th October 2017, 04:52 PM   #75
billshurv is offline billshurv  United Kingdom
diyAudio Member
 
billshurv's Avatar
 
Join Date: Mar 2014
Why not ground everything straight to chassis?
Quote:
Originally Posted by uzernaam View Post
If you look closely at the black wires soldered to the shield tabs, you can see strands of the ground wire running right next to them soldered to the same point.

I did this per tomchr's instructions here:
I saw that, but on the offchange that the RCAs are accidentally also connecting to the case a flying lead direct to the miniDSP is a worthwhile check. We know that works as miniDSP is used quite a bit with the Mod-86.
  Reply With Quote
Old 20th October 2017, 05:08 PM   #76
uzernaam is offline uzernaam  United States
diyAudio Member
 
uzernaam's Avatar
 
Join Date: Oct 2010
Location: Phoenix Arizona USA
Ok,

First I'd like to thank everyone for their contributions and effort. None of you get paid for what you do here, so I hope it's at least been interesting and fun.

Second, I've discovered a phenomenon I simply can't explain. I left the amp playing all night last night in the garage because I was simply too tired late in the night to have remembered to go back and turn it off after I made a trip to the loo.

I came back in to check on it this morning after I noticed sound coming from the direction of the garage. I walked in and listened for a bit and thought "sure sounds great, wish it didn't have noise." I turned the volume down in preparation to shut everything off and didn't hear anything.

After a good 15 minutes of touching, adjusting, turning on and off, and general screwing-around-with this morning... I've discovered I now have an amp that is near-silent. The little bit of noise that's left is low enough that I can't hear it any further away than about 2 feet from the speakers.

I swear to all that is holy I didn't change a thing from the last time I heard noise in this system. All I did is let it play overnight.

I've just moved it back into my listening room, and it's still working great connected to PC, miniDSP.

All I can do right now is shake my head, call myself lucky, and thank all of you.

And Tom, great work. As I said, these amp boards sound fantastic.
  Reply With Quote
Old 20th October 2017, 05:23 PM   #77
billshurv is offline billshurv  United Kingdom
diyAudio Member
 
billshurv's Avatar
 
Join Date: Mar 2014
Why not ground everything straight to chassis?
Great news. Fingers crossed it stays that way.
  Reply With Quote
Old 20th October 2017, 05:32 PM   #78
scottjoplin is offline scottjoplin  Wales
diyAudio Member
 
scottjoplin's Avatar
 
Join Date: Dec 2015
Location: Penrhyndeudraeth
The only thing that springs to mind is a poor connection to ground somewhere
__________________
Woofer Assisted Wideband is the New Testament renounce the anachronistic acronym FAST
  Reply With Quote
Old 20th October 2017, 05:50 PM   #79
tom2016 is offline tom2016
diyAudio Member
 
Join Date: Feb 2016
Two things spring to mind when you told me this. The first thing is that you may have a bad capacitor somewhere and it charged up by being on for an extended period of time. The other thing that comes to mind is a thermally related issue where once things warmed up they expanded and a connection was made perhaps a bad resistor somewhere. When I have these sorts of problems I cool the unit down and then use a heat gun at certain spots to find the problem. If your problem doesn't return then all is good.
  Reply With Quote
Old 20th October 2017, 05:51 PM   #80
tom2016 is offline tom2016
diyAudio Member
 
Join Date: Feb 2016
One more thing. Jiggle all connections vigorously before you put that cover on.
  Reply With Quote

Reply


Why not ground everything straight to chassis?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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Should I directly connect my signal ground to chassis ground? Bricolo Solid State 4 18th March 2014 10:42 PM
Voltage between chassis ground and earth ground haselphlunk Instruments and Amps 17 19th November 2012 05:21 AM
TT signal ground v. chassis ground and hummmmmmm texaslonghorn Analogue Source 0 25th November 2009 03:30 AM
~14 VDC between chassis ground and signal ground... StalfoS Chip Amps 3 5th May 2007 09:26 PM
Chassis Ground = Circuit Ground --> Problems? rhildenbrand Pass Labs 5 23rd April 2004 02:08 AM


New To Site? Need Help?

All times are GMT. The time now is 02:06 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio
Wiki