What do I see on my scope? - diyAudio
Go Back   Home > Forums > Design & Build > Parts

Parts Where to get, and how to make the best bits. PCB's, caps, transformers, etc.

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 28th December 2006, 08:14 PM   #1
diyAudio Member
 
Onvinyl's Avatar
 
Join Date: Aug 2002
Location: Germany
Default What do I see on my scope?

While checking an amp, feeding it with a pure sine wave, I can see that sine wave in ok shape but painted in a thick line. What should that tell me?
Without a signal, the amp shows only background noise,
Rüdiger
__________________
"I can feel what's going on inside a piece of electronic equipment. I have a sense that I know what's going on inside the transistors." Robert Moog
  Reply With Quote
Old 28th December 2006, 08:23 PM   #2
diyAudio Moderator
 
pinkmouse's Avatar
 
Join Date: Apr 2002
Location: Chatham, England
Oscillation.
__________________
Rick: Oh Cliff / Sometimes it must be difficult not to feel as if / You really are a cliff / when fascists keep trying to push you over it! / Are they the lemmings / Or are you, Cliff? / Or are you Cliff?
  Reply With Quote
Old 28th December 2006, 09:21 PM   #3
diyAudio Member
 
Onvinyl's Avatar
 
Join Date: Aug 2002
Location: Germany
Argh, always my darkest dreams come true
Rüdiger
__________________
"I can feel what's going on inside a piece of electronic equipment. I have a sense that I know what's going on inside the transistors." Robert Moog
  Reply With Quote
Old 28th December 2006, 10:39 PM   #4
diyAudio Moderator
 
pinkmouse's Avatar
 
Join Date: Apr 2002
Location: Chatham, England
It may not be as bad as you fear. That kind of problem with low level oscillation may well be solvable by lead dress or better PSU decoupling.
__________________
Rick: Oh Cliff / Sometimes it must be difficult not to feel as if / You really are a cliff / when fascists keep trying to push you over it! / Are they the lemmings / Or are you, Cliff? / Or are you Cliff?
  Reply With Quote
Old 28th December 2006, 10:40 PM   #5
diyAudio Member
 
Join Date: Jan 2006
Location: Fairmount, GA
Harmonics?
__________________
Poor stereo mix? Switch to mono! Perfect.
  Reply With Quote
Old 28th December 2006, 10:47 PM   #6
diyAudio Moderator
 
pinkmouse's Avatar
 
Join Date: Apr 2002
Location: Chatham, England
Quote:
Originally posted by davidlzimmer
Harmonics?
Possibly. Crank up the time base on the scope and see if you can resolve a waveform. If it's harmonics then it will likely not be that much higher in frequency. Harmonics will also change with the input frequency, wheras oscillation is unlikely to. However, I personally have never had a problem like this due to harmonic distortion, but there's always a first time!
__________________
Rick: Oh Cliff / Sometimes it must be difficult not to feel as if / You really are a cliff / when fascists keep trying to push you over it! / Are they the lemmings / Or are you, Cliff? / Or are you Cliff?
  Reply With Quote
Old 28th December 2006, 11:46 PM   #7
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Depending on the test frequency, it can also be hum/ripple. Try synching to the line and play with the trigger level to see if there's some low frequency stuff in there.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 29th December 2006, 04:16 AM   #8
diyAudio Member
 
I_Forgot's Avatar
 
Join Date: Jan 2005
Location: Phoenix, Az.
It may also be a crappy scope. A lot of old scopes get fuzzy as the capacitors in their power supplies go bad. A good scope will display a thin, sharply focused line. Does the scope have a 1 kHz square wave calibration signal you can look at?

I_F
  Reply With Quote
Old 29th December 2006, 04:43 AM   #9
Pano is offline Pano  United States
diyAudio Moderator
 
Pano's Avatar
 
Join Date: Oct 2004
Location: Milliways
Blog Entries: 4
If it's a Class-D amp, it the switching RF!
__________________
Take the Speaker Voltage Test!
  Reply With Quote
Old 29th December 2006, 05:41 AM   #10
diyAudio Member
 
Join Date: Apr 2004
Location: 12km off the alaska highway in northern BC
Quote:
What do I see on my scope?
most likely a trick question.


Quote:
What should that tell me?
easy - somethings wrong somewhere


sorry, hard to refrain with question like these....
  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
Great deal on Digital scope. Is this enough scope? hifimaker Pass Labs 1 1st May 2007 09:59 PM
My first scope! bigwill Equipment & Tools 3 7th July 2006 05:10 AM
can your 'scope do this? jackinnj Equipment & Tools 6 30th June 2006 02:21 PM
10 Mhz Scope enough ?? Henrik Juhl Equipment & Tools 24 20th October 2004 06:05 AM


New To Site? Need Help?

All times are GMT. The time now is 05:31 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