tabs touching, no output - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

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 23rd June 2003, 08:26 PM   #1
diyAudio Member
 
Matttcattt's Avatar
 
Join Date: Feb 2003
Location: Bristol
Default tabs touching, no output

has anyone else found that when the tabs of two gainclone chips are conected electrically, one channel has no output? both my gainclones are mouned directly on the heat sink, but they are on seperate heatsinks. today, i tried connecting both heatsinks together with a pice of metal, and one channel stoped working! i immediatly disconnected power, and felt the chips, they were not even warm, so i tried again, with the same result. has anyone else noticed this? i do not know why this would happen, because both tabs are at -v.
__________________
If it aint broke, don't fix it. If it is broke, fix it.
If you can't fix it, take it apart and see how it "worked".
  Reply With Quote
Old 23rd June 2003, 08:40 PM   #2
diyAudio Member
 
Cradle22's Avatar
 
Join Date: Jan 2003
Location: Dortmund, Germany
Hi!

One thing that comes to my mind is that even if you connect both to the same supply, I bet you still use seperated filter caps for supply voltage.

So both ships are not "really" sharing the same supply, because of their own filters...

I will not check this out, but on my P3A I have one toroid, but apart from that totally seperated power supplies... and I bet that my P3A woult not like it very much if I connected V- from one supply with V- from the other...

They still share mass, though...


But maybe someone else can shed more light on this...


Bye,

Arndt
__________________
************************
A Sacrifice For Freedom
  Reply With Quote
Old 23rd June 2003, 09:00 PM   #3
diyAudio Member
 
Matttcattt's Avatar
 
Join Date: Feb 2003
Location: Bristol
no, one chips -v pin is connected directly to the other's -v pin.
__________________
If it aint broke, don't fix it. If it is broke, fix it.
If you can't fix it, take it apart and see how it "worked".
  Reply With Quote
Old 23rd June 2003, 09:38 PM   #4
raindog is offline raindog  Romania
diyAudio Member
 
raindog's Avatar
 
Join Date: May 2003
Location: Timisoara
Send a message via Yahoo to raindog
to what pin is the tab conected (if so?)
  Reply With Quote
Old 24th June 2003, 06:32 AM   #5
diyAudio Member
 
Matttcattt's Avatar
 
Join Date: Feb 2003
Location: Bristol
Quote:
Originally posted by raindog
to what pin is the tab conected (if so?)

pins 3 and 4.
__________________
If it aint broke, don't fix it. If it is broke, fix it.
If you can't fix it, take it apart and see how it "worked".
  Reply With Quote
Old 24th June 2003, 07:51 AM   #6
Jennice is offline Jennice  Denmark
diyAudio Member
 
Join Date: Jun 2003
Location: Planet Earth
Hi folks,

I haven't built a gainclone, so I'm taking a wild guess about the typical IC amp circuits here...

Am I right in assuming that the inputs are (somewhere along the electrical path) connected at the audio source or pre-amp?

In that case the circuits have at least one common reference level.
Connecting the heat sinks (and thereby taps) you create a second common level (more or less). Since this is not at precicely the same potential, it causes a fault current, which is sensed by one of the sensing circuits on the chip. This triggers it's alarm state. This, in turn, shuts off the output to avoid self-destruction or un-intentended operation.

Try checking for multiple electrical paths for the same signals/potentials...

Jens
  Reply With Quote
Old 24th June 2003, 01:52 PM   #7
zobsky is offline zobsky  India
diyAudio Member
 
zobsky's Avatar
 
Join Date: Mar 2002
Location: Dallas, Tx, USA
on the side, ..... does anyone have 2 chips mounted on the same heatsink? ..i thoght i saw some pictures on the www with this arrangement

because this is what i intend to do, ..scrounged a working transformer from an old reciever and got my 3845 chips yesterday.
  Reply With Quote
Old 24th June 2003, 02:05 PM   #8
tiroth is offline tiroth  United States
diyAudio Member
 
Join Date: Dec 2001
Location: Pittsburgh, PA, USA
Generally the chips will be isolated from the heatsinks at any rate. These amps usually stay cool enough that you can afford the insulator.
  Reply With Quote
Old 24th June 2003, 02:11 PM   #9
Banned
 
Join Date: Mar 2003
Location: Lisbon, Portugal
Matttcattt,
You forgot to say what power op-amps are you talking about.
I think you use OPAs, don't you?

I remember reading on one datasheet (don't remember what) that the tabs shouldn't be used do conduct power.
That is to say they should be isolated.
But if you used a single supply (+ and ground) the tabs would be at ground potential and no problems.
  Reply With Quote
Old 24th June 2003, 03:39 PM   #10
diyAudio Member
 
Matttcattt's Avatar
 
Join Date: Feb 2003
Location: Bristol
Quote:
Originally posted by carlosfm
Matttcattt,
You forgot to say what power op-amps are you talking about.
I think you use OPAs, don't you?

I remember reading on one datasheet (don't remember what) that the tabs shouldn't be used do conduct power.
That is to say they should be isolated.
But if you used a single supply (+ and ground) the tabs would be at ground potential and no problems.

oops, forgot

yes, OPA541, free samples
__________________
If it aint broke, don't fix it. If it is broke, fix it.
If you can't fix it, take it apart and see how it "worked".
  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
3C24 in a SE output stage - output transformer impedance recommendation !!! aldovan Tubes / Valves 15 6th September 2008 10:18 AM
Adding secondary of output transformer into cathodes of output stage ? Eico ST-70 freddymac406 Tubes / Valves 3 21st April 2007 06:15 PM
Soldering Binding Posts - Solder Tabs disconnec Multi-Way 5 20th September 2005 02:28 AM
I2S digital output in Marantz CD4000 and four TDA1541A with balance analog output iklari14 Digital Source 30 18th July 2003 12:57 PM


New To Site? Need Help?

All times are GMT. The time now is 03:40 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