• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Sansui 907 DC at speaker terminals

I saw a 907 service manual on Yahoo auction in Japan. But I was too late. It was sold for ¥4000. Yes! I was kicking myself.
 
Been a long time…
I uploaded this AU-a907i service manual. I still have this problem with my AU-a907 (previous version of 907i). If you look in the attached screenshot, you’ll see the circled test points. I can adjust them to be 0v. But it goes up when I connect the amp to 8ohm speakers. I‘ve swapped the two 2sk289 on one side. Checked all the transistors. swapped electrolytic caps. Input to this board doesn’t go up but output does.
What else is there to do?

I got the SM by the way if anyone needs ;)
 

Attachments

  • Open Sansui AU-a907i_sm.jpeg.png
    Open Sansui AU-a907i_sm.jpeg.png
    611.5 KB · Views: 26
Good day you all !!
Can I restart this one more time….
I have this AU—a907. It was produced in 1986. In Japan you can see the service manual here
I’ve replaced all the E-caps And trimpots. Power amp works without a problem when I isolate it. in other words, run it on “powr amp direct” mode. It has no problems on integrated mode either on idle. Output DC is few millivolts. Problem starts when speakers Connected. DC from the pre-amp goes up and amp goes to protection mode. Then it restarts.

What am I missing here?? Could it be a problem someplace else????

I’m desperate and really appreciate any help.
 
Hi bolero
Sorry, I couldn’t reply sooner. I work away from home.
anyways, I checked it and headphones work fine. Problem occurs just on integrated mode when connected to speakers.
help! Help!! Help!!!
 
Well that could be a clue. It looks to me like the headphones take the same signal as the speakers, other than their own dedicated relay ( RL3 ) and kT1 transformer.

I wonder if the speaker relays RL1, RL2 could be culprits? Or switch S8
 
Last edited:
You must log in or register to reply here.
Back
Top Bottom