**UPDATE**
I've got the Bias Current adjustment in-progress...
I immediately found that Initially with VR's 3 & 4 all the way Clockwise, with the Multimeter between the Emitters of each channel, they were over 15V!! [Holy crap!]
I Cranked the VR's COUNTER Clockwise, down to about 1/3 from being all the way Counter-Clockwise. I am warming-up that amp now, with the Multimeter on the Left Channel.
I'm Monitoring the mV on that channel's emitters, and the mV's are Dropping.
I got it to about 13.2, which moved around abit. It's fallen in the last 5 minutes to about 11.2mV. This is the Left Channel. I cannot feel any heat from the amp yet!! :^D
I've been told that the Bias Current actually goes Up. And I know this is mV.
But what did you get you mV (Or mA) up to on your Bias Current Redrooster??
I've got the Bias Current adjustment in-progress...
I immediately found that Initially with VR's 3 & 4 all the way Clockwise, with the Multimeter between the Emitters of each channel, they were over 15V!! [Holy crap!]
I Cranked the VR's COUNTER Clockwise, down to about 1/3 from being all the way Counter-Clockwise. I am warming-up that amp now, with the Multimeter on the Left Channel.
I'm Monitoring the mV on that channel's emitters, and the mV's are Dropping.
I got it to about 13.2, which moved around abit. It's fallen in the last 5 minutes to about 11.2mV. This is the Left Channel. I cannot feel any heat from the amp yet!! :^D
I've been told that the Bias Current actually goes Up. And I know this is mV.
But what did you get you mV (Or mA) up to on your Bias Current Redrooster??
Are you serious? The photo shows one heatsink on and the other one off and sitting on the capacitors so you can see where it goes? It goes on the heatsink thats already there on the transistor,it just makes it better by disappaiting more heat. The 5W resistors have nothing to do with it.I mentioned them because they give off a lot of heat
Have a good look at the photo and what do you see? Youll see a computer heatsink thats been taken off another transistors heatsink and its sitting on the caps next to it,expressly put there so you can see where it came from and how it was attached. The other computer heatsink is still attached to the other transistor heatsink. So you have two heatsinks, one on and one off to show you how it goes on.The little square on the computer heatsink fits into the little square hole on the transistor heatsink.
NEW Sansui AU-11000 Adjustments with F-2583 Bias Board!! :^)
THIS is my Finalized Version!! Altered Trim-Directions for VR03 & VR04, as well as Corrected DC-Offset & Bias Current Trim Labels on Figure 3-2. Board #'s are changed to F-2583.
I also switched the order of operation, so that Bias Current comes first.
Figure 3-1 has been changed to show Multimeter Leads going to Terminals for Speaker A instead of B.
Hopefully, this will help someone out in the Future....
THIS is my Finalized Version!! Altered Trim-Directions for VR03 & VR04, as well as Corrected DC-Offset & Bias Current Trim Labels on Figure 3-2. Board #'s are changed to F-2583.
I also switched the order of operation, so that Bias Current comes first.
Figure 3-1 has been changed to show Multimeter Leads going to Terminals for Speaker A instead of B.
Hopefully, this will help someone out in the Future....
Attachments
![Sansui AU-11000 Output Adustments [F-2583] [CORRECTED!].PNG](/community/data/attachments/518/518246-340709131007bfcca7288ae0afad2352.jpg)
Yes - That's why I changed it to Counter-Clockwise as shown in my UPDATED Adjustments Procedure in the Pic Above.
WTF? Are you serious? How can you not comprehend that! And another thing youve hijacked my thread.How about starting your own because Im trying to get my own amplifier going.
**Update**
After completing the Bias Current Adjustment, via measuring mV from the Transistor Emitters, I Zeroed the DC-Offset.
I took 3 Hours to get the Bias Current to the Tightest and most Stable Spec at around 20.3mA. (measuring ~13.3mV at the Emitters of each Channel)
It took only 30 minutes to adjust the DC-Offset.
It seems the Bias Current floats around abit, even after the Amp was on for over 2 hours. It seemed that anything below 13.2mV was Dropping allot, and anything above 3.5mV was going up quite abit.
I could have just called it good enough between 13 & 14mV. But I wanted to see if I could make it as Stable as Possible. And I did it, though it took WAY longer than I anticipated.
I also got the DC-Offset down to below the ±10mV Spec, floating between -.7mV & .8mV.
I didn't get a chance yet to actually connect Speakers and an Input-Source yet to actually listen to it. It should sound Amazing, since I definitely got it to Tighter-Specs than required. Hopefully no noise/THD. Before opening it up weeks ago, it has some 'snow' in the background. That should be totally Gone now.
But I can Definitely say that after over 3 hours of Operation at Minimum-Volume while doing the Adjustments, this amp doesn't overheat anymore!
I think that the VR-Trims, which are OEM rivet-style, would be Better if they were Multi-Turn. Fine-Tuning this Amp would have Probably taken less than HALF the time it took me, if I had replaced the Trims. But, the original ones work. And I guess my Philosophy is, that if it isn't causing a problem, then don't 'Fix' it. Especially in my years of experience working on TV's and Audio-Sources, replacing things that Work tends to result in unwanted results.
Replacing all 8 of the Sanken TO3 Power-Transistors with OnSemi MJ21193's & 94's, as well as all the Electrolytic Caps on the Bias Board solved the true Initial Problems once I PROPERLY Adjusted the Bias Current.
Although the Initial Overheating Issue was due to Intermittent Shorting of 2 of the Sanken Power-Amp Transistors, the overheating after replacing all of them & all 14 Caps on the Bias Board was due to a Misguided Service Manual Procedure for setting the Bias-Current. Which is Required when replacing critical things like Power-Transistors.
Had the Service Manual been at least Mostly Correct, this would have been WAY Less of a headache.
None-the-less, I now have learned how to PROPERLY set Bias-Current on Sansui AU-11000's with the F-2583 Bias-Board. And Yes - That is a Major Difference from the F-2580 shown in the Service Manual!
It still makes me wonder why the Service Manual doesn't even mention that there is ANY Different Procedure for AU-9900's or AU-11000's with different Bias Boards. Sansui knew what boards they were using, but didn't have an appropriate Service Manual for everyone.
This makes me wonder how many Techs back in the day ran into the SAME Issues when working on this Amp. If the Service Manual was wrong for just 20% of these AU-11000's, just think of the number of Techs who just gave it back to the customer, and moved on to the next.
I have worked on a few Amps in the past, and have replaced allot of Capacitors, Diodes and burnt Resistors, etc. But never ran into an Amp with an incorrect adjustment procedure that was SO Far Off, that it would cause potential damage to the Unit.
Typically, a Manufacture makes sure they're Service Manual the provide is 99% Accurate not just for legal reasons, but because they're in-house Technicians who Assemble & Adjust the Amp from the Factory use the same Guidelines. Clearly, there was a serious error at some point. And I'd doubt it was Japanese to English-Translation.
I wonder if this Amp is just not 'Popular' enough to have mattered enough to the Manufacture to have an accurate Service Manual.
I've also looked at Schematics, and notice differences not only in Components, but in the Circuit itself.
For example, the F-2583 has 14 Electrolytic Capacitors, 2 of which are Non-Polar. The Schematic in the Service Manual for the F-2580 shows only 8 Electrolytic Capacitors. There are also different Resistors on the F-2582 board in this amp, which go to the Headphone Jack. And although most of the Pictures I've seen on this site and others of the Bias Board & Cables show that there are Plug-in Interfaces for all of the wiring to and from the F-2580/F-2583, THIS AU-11000 has only 4 of them, leaving 12 Wires which are Soldiered. And this Amp doesn't appear to have any signs of being serviced before. (I can usually tell)
I think it's Important that my Corrected Bias-Current & DC-Offset Adjustment Page be Added to the Service Manual. Even though I didn't change the Method on that page for reading off the Emitters instead of the Power Supply, the fact that the VR-Trims are properly Labeled for the F-2583, turning VR03 & VR04 Counter-Clockwise for Minimum instead of Clockwise, Bias Current adjustment comes before DC-Offset instead of the opposite, and that the DC-Offset measurement should be taken from Speakers-A and not Speakers-B.
(The Last one isn't that big a deal, but worth noting since Figure 3-2 ORIGINALLY showed connecting the Leads to Speaker B)
If anyone would like to Share this with others who would Benefit from this Corrected Information, that would be Appreciated. More for others than myself. No one should have to run into Faulty Service Manuals. And if this keeps people's Sansui Amps alive, then that is a Wonderful Thing. Cause that keeps them happy. No one likes to hit the bricks, and throw-away a perfectly good Amp that needs Properly Serviced. And all because the Manufacture only provided enough Information to those who have a 'Specific' Bias Board.
If anyone has any Further Advice, feel free to Post-Up!! Knowledge is Power!
Spread the Word, and don't leave people Disappointed just because they run into a BS Service Manual!!
After completing the Bias Current Adjustment, via measuring mV from the Transistor Emitters, I Zeroed the DC-Offset.
I took 3 Hours to get the Bias Current to the Tightest and most Stable Spec at around 20.3mA. (measuring ~13.3mV at the Emitters of each Channel)
It took only 30 minutes to adjust the DC-Offset.
It seems the Bias Current floats around abit, even after the Amp was on for over 2 hours. It seemed that anything below 13.2mV was Dropping allot, and anything above 3.5mV was going up quite abit.
I could have just called it good enough between 13 & 14mV. But I wanted to see if I could make it as Stable as Possible. And I did it, though it took WAY longer than I anticipated.
I also got the DC-Offset down to below the ±10mV Spec, floating between -.7mV & .8mV.
I didn't get a chance yet to actually connect Speakers and an Input-Source yet to actually listen to it. It should sound Amazing, since I definitely got it to Tighter-Specs than required. Hopefully no noise/THD. Before opening it up weeks ago, it has some 'snow' in the background. That should be totally Gone now.
But I can Definitely say that after over 3 hours of Operation at Minimum-Volume while doing the Adjustments, this amp doesn't overheat anymore!
I think that the VR-Trims, which are OEM rivet-style, would be Better if they were Multi-Turn. Fine-Tuning this Amp would have Probably taken less than HALF the time it took me, if I had replaced the Trims. But, the original ones work. And I guess my Philosophy is, that if it isn't causing a problem, then don't 'Fix' it. Especially in my years of experience working on TV's and Audio-Sources, replacing things that Work tends to result in unwanted results.
Replacing all 8 of the Sanken TO3 Power-Transistors with OnSemi MJ21193's & 94's, as well as all the Electrolytic Caps on the Bias Board solved the true Initial Problems once I PROPERLY Adjusted the Bias Current.
Although the Initial Overheating Issue was due to Intermittent Shorting of 2 of the Sanken Power-Amp Transistors, the overheating after replacing all of them & all 14 Caps on the Bias Board was due to a Misguided Service Manual Procedure for setting the Bias-Current. Which is Required when replacing critical things like Power-Transistors.
Had the Service Manual been at least Mostly Correct, this would have been WAY Less of a headache.
None-the-less, I now have learned how to PROPERLY set Bias-Current on Sansui AU-11000's with the F-2583 Bias-Board. And Yes - That is a Major Difference from the F-2580 shown in the Service Manual!
It still makes me wonder why the Service Manual doesn't even mention that there is ANY Different Procedure for AU-9900's or AU-11000's with different Bias Boards. Sansui knew what boards they were using, but didn't have an appropriate Service Manual for everyone.
This makes me wonder how many Techs back in the day ran into the SAME Issues when working on this Amp. If the Service Manual was wrong for just 20% of these AU-11000's, just think of the number of Techs who just gave it back to the customer, and moved on to the next.
I have worked on a few Amps in the past, and have replaced allot of Capacitors, Diodes and burnt Resistors, etc. But never ran into an Amp with an incorrect adjustment procedure that was SO Far Off, that it would cause potential damage to the Unit.
Typically, a Manufacture makes sure they're Service Manual the provide is 99% Accurate not just for legal reasons, but because they're in-house Technicians who Assemble & Adjust the Amp from the Factory use the same Guidelines. Clearly, there was a serious error at some point. And I'd doubt it was Japanese to English-Translation.
I wonder if this Amp is just not 'Popular' enough to have mattered enough to the Manufacture to have an accurate Service Manual.
I've also looked at Schematics, and notice differences not only in Components, but in the Circuit itself.
For example, the F-2583 has 14 Electrolytic Capacitors, 2 of which are Non-Polar. The Schematic in the Service Manual for the F-2580 shows only 8 Electrolytic Capacitors. There are also different Resistors on the F-2582 board in this amp, which go to the Headphone Jack. And although most of the Pictures I've seen on this site and others of the Bias Board & Cables show that there are Plug-in Interfaces for all of the wiring to and from the F-2580/F-2583, THIS AU-11000 has only 4 of them, leaving 12 Wires which are Soldiered. And this Amp doesn't appear to have any signs of being serviced before. (I can usually tell)
I think it's Important that my Corrected Bias-Current & DC-Offset Adjustment Page be Added to the Service Manual. Even though I didn't change the Method on that page for reading off the Emitters instead of the Power Supply, the fact that the VR-Trims are properly Labeled for the F-2583, turning VR03 & VR04 Counter-Clockwise for Minimum instead of Clockwise, Bias Current adjustment comes before DC-Offset instead of the opposite, and that the DC-Offset measurement should be taken from Speakers-A and not Speakers-B.
(The Last one isn't that big a deal, but worth noting since Figure 3-2 ORIGINALLY showed connecting the Leads to Speaker B)
If anyone would like to Share this with others who would Benefit from this Corrected Information, that would be Appreciated. More for others than myself. No one should have to run into Faulty Service Manuals. And if this keeps people's Sansui Amps alive, then that is a Wonderful Thing. Cause that keeps them happy. No one likes to hit the bricks, and throw-away a perfectly good Amp that needs Properly Serviced. And all because the Manufacture only provided enough Information to those who have a 'Specific' Bias Board.
If anyone has any Further Advice, feel free to Post-Up!! Knowledge is Power!
Spread the Word, and don't leave people Disappointed just because they run into a BS Service Manual!!
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