Yamaha M-80 - 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 10th February 2006, 06:01 PM   #1
Tejaus is offline Tejaus  United States
diyAudio Member
 
Join Date: Oct 2005
Default Yamaha M-80

I had originally posted this under EW's dc offset thread on Audiokarma but I thought it might be kinda buried there. Any help would be appreciated as these amps are chock full of components. I have a service manual and am planning on doing a recap since these amps double as space heaters.


I have adjusted the bias per the service manual to 15.5mV +/- 1mv and now have about 50mV dc offset on the left channel still. It will start out around 29mV then increase as the amp gets hotter. The left channel is also running about 10 degrees hotter than the right channel. The right heatsink measures about 147, the left about 157 degrees at idle. The manual also states for confirmation of Auto-A function using the same emitter resistors test points that the bias should increase to more than 31mV when you turn on the Auto A button. However, I get only a very slight increase, just to over 16mV then back down to 15.7mV. This happens on both channels so I'm not sure what's going on. Anyone have any ideas?
  Reply With Quote
Old 10th February 2006, 06:21 PM   #2
diyAudio Member
 
Tube_Dude's Avatar
 
Join Date: Mar 2002
Location: Aveiro-Portugal
Default Re: Yamaha M-80

Quote:
Originally posted by Tejaus



I have adjusted the bias per the service manual to 15.5mV +/- 1mv and now have about 50mV dc offset on the left channel still.

Hi Tejaus

-Have the offset begun only after the bias adjustement?

-Have the M80 a pot for adjusting the offset?

- What are the value of the emitters resistors (where you have measured the bias ).?

But anyway , 50mV offset voltage is nothing to worry about...
__________________
Jorge
  Reply With Quote
Old 11th February 2006, 03:24 AM   #3
Tejaus is offline Tejaus  United States
diyAudio Member
 
Join Date: Oct 2005
Jorge,

The offset was there before I did the bias adjustment. I was having issues with the protection circuit not releasing when I would first turn it on. I traced that problem to the adhesive used to glue the 1000uf 100v caps to the board. The right channel doesn't have any dc offset at all so I would like to get the left channel to match.
  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
Yamaha AX-930 jleaman Analogue Source 6 21st November 2010 11:43 AM
Yamaha cdx 900 stex Digital Source 4 23rd January 2010 11:44 AM
Yamaha RX-777 quasi Solid State 4 15th November 2007 12:58 PM
Yamaha A-550 angel Solid State 4 18th January 2006 01:22 AM
Yamaha CDX-490 newbie123 Digital Source 1 3rd December 2005 03:31 PM


New To Site? Need Help?

All times are GMT. The time now is 12:58 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