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.

Need help with a Rotel RA-970BX
Need help with a Rotel RA-970BX
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 1st May 2014, 10:03 AM   #1
dryphtyr is offline dryphtyr
diyAudio Member
 
Join Date: May 2014
Location: South of the Mason-Dixon
Unhappy Need help with a Rotel RA-970BX

I purchased my 970BX new & got quite a few years of use out of it before it died. I don't trust any local shops to do the work, so my only viable options are to send it to Rotel or to learn how to fix it myself. I could almost buy a new amp for what it would cost for shipping + repair cost to them, so I would appreciate any help I can get. I'm very good with electrical systems & have all the tools needed to get the job done. Unfortunately, I am barely a novice when it comes to troubleshooting electronics. I also already have the technical manual for it.

Anyway, the problem is that one channel has almost no output. It outputs at very low volume & has a bunch of static. Also, when I connect a DMM to that speaker tap, It shows a couple volts DC. I know enough to know this is bad, but beyond that, I don't know where to start. I don't want to have to de-solder & test every component if I don't have to. Hopefully someone can point me in the right direction.

If you need more detail, ask away.

Thanks in advance
  Reply With Quote
Old 1st May 2014, 11:20 AM   #2
wintermute is online now wintermute  Australia
just another
diyAudio Moderator
 
wintermute's Avatar
 
Join Date: Aug 2003
Location: Sydney
Need help with a Rotel RA-970BX
First thing that I would check is the volume pot. The wiper may not be making good contact with the track. Put the multimeter across one end and the wiper (middle pin) and check the resistance whilst varying the volume position.

I believe that an open wiper can also cause DC on the output due to the input not having a reference to ground.

edit: assuming of course it has a pot and is not digital volume!

Tony.
__________________
Any intelligence I may appear to have is purely artificial!
Some of my photos

Last edited by wintermute; 1st May 2014 at 11:21 AM. Reason: comment about whether it has a pot...
  Reply With Quote
Old 1st May 2014, 11:36 AM   #3
dryphtyr is offline dryphtyr
diyAudio Member
 
Join Date: May 2014
Location: South of the Mason-Dixon
Will do. I'm going to take it with me to the shop today. This is probably important, but it also had a blown fuse. I had replaced it at the time that it died, but it seems that it's missing one now. It's been probably 10 years since I've messed with it, so I'm a bit foggy on all the specifics of it. If I can find a suitable replacement in town, I'll check it out today. If I have to order one, it'll be a few days. Also, this amp is pure old school AB analog, so it's a kind of standard volume pot. The only difference is that it's a split pot, so left & right can be adjusted independently. It has 6 pins on it, so I'm assuming each set of 3 corresponds to one channel. I'll keep you posted.
  Reply With Quote
Old 1st May 2014, 11:53 AM   #4
JonSnell Electronic is offline JonSnell Electronic  United Kingdom
diyAudio Member
 
JonSnell Electronic's Avatar
 
Join Date: Dec 2012
Location: The Jurassic Coast, England. GB
In the first instance I would check for leakage, C601,602,687 and 688
__________________
Support for Fender, Marshall and all Valve Equipment; Audio Innovations, Audiorama FU29, Quad and Leak. www.jonsnell.co.uk
  Reply With Quote
Old 1st May 2014, 12:09 PM   #5
dryphtyr is offline dryphtyr
diyAudio Member
 
Join Date: May 2014
Location: South of the Mason-Dixon
Ok, 601 & 602 appear ok, unless there's a check I need to do with the meter. The two above those appear suspect. I didn't see the other 2 that you mentioned on the circuit board. 909 & 910 on the ps side also appear suspect. Thoughts? Keep in mind, I'm a total beginner at this kind of thing, so baby steps. Thanks
Attached Images
File Type: jpg 20140501_070403.jpg (982.8 KB, 134 views)
File Type: jpg 20140501_070310.jpg (891.1 KB, 116 views)
  Reply With Quote
Old 1st May 2014, 12:59 PM   #6
wintermute is online now wintermute  Australia
just another
diyAudio Moderator
 
wintermute's Avatar
 
Join Date: Aug 2003
Location: Sydney
Need help with a Rotel RA-970BX
Oh those caps look like they have leaked badly! You will probably want to at least remove and clean up the components that have had the electrolite around them as well. Test them whilst they are out!

Tony.
__________________
Any intelligence I may appear to have is purely artificial!
Some of my photos
  Reply With Quote
Old 1st May 2014, 01:05 PM   #7
dryphtyr is offline dryphtyr
diyAudio Member
 
Join Date: May 2014
Location: South of the Mason-Dixon
Will do. I just picked up crc contact cleaner & I found some glass fuses. Is there any reason not to use those temporarily until I get new ceramic ones ordered? I'll pull the bad components off & give it a good cleaning. Then I'll order replacement parts.
  Reply With Quote
Old 1st May 2014, 01:14 PM   #8
Max Headroom is online now Max Headroom  Australia
diyAudio Member
 
Max Headroom's Avatar
 
Join Date: Jan 2013
Location: West Australia, near to the beach, natural ambient sounds mostly.
Need help with a Rotel RA-970BX
Quote:
Originally Posted by wintermute View Post
Oh those caps look like they have leaked badly! You will probably want to at least remove and clean up the components that have had the electrolite around them as well. Test them whilst they are out!

Tony.
That is contact glue.....sheesh.

Dan.
  Reply With Quote
Old 1st May 2014, 01:33 PM   #9
wintermute is online now wintermute  Australia
just another
diyAudio Moderator
 
wintermute's Avatar
 
Join Date: Aug 2003
Location: Sydney
Need help with a Rotel RA-970BX
That was what I first thought but I couldn't understand why they would put it there and in such a wide patch...

The resistor legs appear to be corroded, or is that just my colourblindness?

Tony.
Attached Images
File Type: png leakage.png (83.7 KB, 100 views)
__________________
Any intelligence I may appear to have is purely artificial!
Some of my photos
  Reply With Quote
Old 1st May 2014, 01:40 PM   #10
dryphtyr is offline dryphtyr
diyAudio Member
 
Join Date: May 2014
Location: South of the Mason-Dixon
It doesn't appear to be corrosion. If the consensus is that it's just glue, then back to my other questions: crc contact cleaner to clean the board & glass fuses to temporarily substitute for ceramic? I'm at the shop now, so as long as the fuses are acceptable, I can plug it in give precise readings with the DMM
  Reply With Quote

Reply


Need help with a Rotel RA-970BXHide 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
Rotel RA-970BX problems Audiojinxed Solid State 5 6th April 2013 06:40 PM
Bypassing tone switch on Rotel RA-931 and RA-930AX lars667 Solid State 6 10th June 2012 03:39 PM
Rotel RB-970BX Upgrade? bug2k11 Solid State 10 8th September 2011 02:58 PM
Rotel RA-970BX schematic needed agoraphobic Solid State 2 26th June 2010 09:15 AM
schematics of Rotel RA-971mk11 / RA-971 digitaldiablo Solid State 0 12th June 2003 04:03 PM


New To Site? Need Help?

All times are GMT. The time now is 08:18 AM.


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