New AU-11000 score, no sound left channel.....

Committed

My smoke got out again
So it's been an incredible week on craigslist. Picked up a Sansui AU-X501 and JBL L100T's in mint condition, minus a refoam needed for the woofs. Also picked up this AU-11000 which was very dirty and only plays on the right channel. I've always wanted one and this one cost me nothing.

Hooked up some test speakers and it played real well out of the right channel. There is some sound out of the left but it is very faint and you have to crank it all the way up to hear. No static or popping.

So I cleaned it up last night, cleaned all the pots and switches and gave it a once over. Found fuse #F604 on the power supply board for driver amp is blown. Also noticed 2 caps that look pretty toasty(in pics below) on what I think is the protector circuit board. DC offset was 2 - 10 mv on the right channel(was floating up and down) and -14mv on the left channel. I don't have a bias reading yet as the manual had me a little confused where to check at. Hoping someone here can direct me to the right contact points.

I'm dying to get this running. I think it will be a good match for the L100T's. Got the woofers for those packed up today and sending them out to Midwest speaker this week. Any advice on where to start on the 11000 is much appreciated. I'd like to get as much done myself as I can. I'm no tech
but I can read a schematic and know how to solder. I had a year of electronics in my first year of college back in 1981.

Or maybe I should just bite the bullet and send it to someone, I guess that depends on what it will take to get it running. If it's simple stuff I can handle it and rather do it myself. This one's for sure a keeper for me so I'd like it in good shape. Recommendations?

Thanks in advance! Scott



The fuse that is blown, screwdriver is pointed to it.



Found these dark burnt looking spots on the back side of the power supply board for driver amp. The burnt spots are at each end of D601 diode, which is near the burnt fuse.



Here's the 2 caps that look bad on the protection board. The other side is burnt brown, wanted to post this side for the markings.

 
Scott,
The unit obviously comes out of protection so the protection THINKS the power amp is ok. On the side there is a pre / main switch, this connects the preamp to the main amp...
1) Take an iPod put it in the AMP in jacks ( KEEP THE IPOD VERY LOW LEVEL) this will be going into the power amp stage with NO gain control. See if both channels play. You MIGHT need to excersice & spray that switch as well.

IF that works try the pre amp out into another power amp (If available) and see if you have both channels works. If the pre doesn't pass signal... try to switch the filters in & out, same with the tone / filter. the BROWN goo is the dreaded Sansui glue.. which ( in this state ) turns mildly acidic and does eat into and thru the leads of diodes and resistors... etc etc. so that bears close inspection. otherwise looks GREAT
 
Additional... not " burn " marks... maybe a cap leaking...
Sometimes the protection relay will not make " proper connection " and it's worse after the unit sits.. for a LONG time... give it a tap and see if that helps ( upper left of 2nd pix )
 
ok so with ipod hooked to "main in" and switch set to "separated" both channels are working.

I did replace the blown fuse mentioned above and it blew immediately after turning it on.
 
Additional... not " burn " marks... maybe a cap leaking...
Sometimes the protection relay will not make " proper connection " and it's worse after the unit sits.. for a LONG time... give it a tap and see if that helps ( upper left of 2nd pix )

It powers up just fine and comes out of protection. The 4 contacts in the protection module thing are all kicking in and look to be making good contact. Something is letting too much current flow through that fuse. Voltage on the supply side of all the fuses is the same. There is a diode right next to those fuses that looks fried, it's the one with the dark marks on the traces on the backside. Looks like it got real hot. Probably replace that for starters.
 
That fuse is part of the protection circuit.....
3 seconds ( or more ) post turn on... do you hear a relay CLICK
Does the LED go green ?
 
That fuse is part of the protection circuit.....
3 seconds ( or more ) post turn on... do you hear a relay CLICK
Does the LED go green ?

Yes the relay clicks and light goes green. At that time I can play on the right channel. The fuse however blows instantly after turning the power on.

Agreed petehall, need to find the cause of the fuse blowing.
 
Power down take out the BLOWN fuse
measure the diode (s) ...
You do have a meter that has a diode check in it .... correct?
 
Yes, out of D601 - D606 they are all good except for 603 is shorted. I didn't disconnect any of them though.
 
Well that's a different kettle O fish

That is preamp power
 

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