Sansui AU-9900 / AU-11000 Repairs

[dr*audio]

I know this is an older post but I would like to know if the onsemi mje350 and mje340 transistors would be suitable substitutes for failure prone motorola uni-watt transistors

Those should be fine. I don't know why there is no bandwidth rating for them on the data sheet. This concerns me because if the bandwidth is lower than the original part it could cause the amp to become unstable and oscillate.

 

[miromustang]

MJD340,Electrically Similar to Popular MJE340 and MJE350...
http://www.onsemi.com/pub_link/Collateral/MJD340-D.PDF

 

[dr*audio]

If they are made with the same die, then they should have the same Ft of 10MHz which is fine.

 

[miromustang]

If they are made with the same die, then they should have the same Ft of 10MHz which is fine.

Thank you very much dr*audio!

 

[miromustang]

I have another question regarding transistors. Which are those critical transistors? On pre-driver boad I noticed that there are 2*C1124, 2*A706, 2*C1628-0, 2*818-0. Which of those should be replaced? I also noticed C1124 and A706 transisor on relay board.

 

[dr*audio]

I have another question regarding transistors. Which are those critical transistors? On pre-driver boad I noticed that there are 2*C1124, 2*A706, 2*C1628-0, 2*818-0. Which of those should be replaced? I also noticed C1124 and A706 transisor on relay board.

All the transistors that look like this should be replaced.

 

[Jcatsweeney]

Hello, Looking for some help here... I have a Sansui AU-9900A that my service guy has had for over a year now. It does work but seems to run very hot on one channel. Is that normal for the A series or can this be a result of bad transistors or improper Bias adjustment?

 

[Binkman]

Hello, Looking for some help here... I have a Sansui AU-9900A that my service guy has had for over a year now. It does work but seems to run very hot on one channel. Is that normal for the A series or can this be a result of bad transistors or improper Bias adjustment?

welcome to AK but start your own thread? However it seems your 'service guy' has been 'enjoying' your piece of equipment for "over a year"?
.....????
bink

 

[Rotoflex4]

Hello, I was wondering if someone might be able to confirm for me that I have this set up correctly (see pic). I'm trying to check/set the bias on my AU-11000 as per the instructions earlier in this thread. I believe I have the alligator clips in the correct positions (at the bottom of the resistors which corresponds to the emitters of the transistor pair). If I have this correct, I should be looking for 13.2mv DC on my DMM? I realize I need to have the bottom on with the feet and the cover also, etc). Thanks!

 

[Binkman]

Greetings; I suggest you pm dr. audio.

 

[Rotoflex4]

Greetings; I suggest you pm dr. audio.

Thanks...I'll try that.

 

[dr*audio]

I have been meaning to include pictures of the ground mod. Now I have an AU-11000A on the bench so I took some pictures. To recap, there is a screw beneath the front panel that completes the ground path for some of the preamp circuitry. As I recall, if it gets loose you lose audio or the tone controls don't work or something odd like that. To get to the screw you have to remove the front panel. It's smarter and a more reliable fix to simply solder a ground braid from the pc board to the chassis. Here's the location of the screw:

To add the braid, scrape the soldermask off the board and scrape the plating off the inner front panel where shown below:

Now solder a braid to both places. Use a large soldering iron tip or a solder gun but do not overheat the board. Apply solder to the chassis first, using plenty of heat to make sure the solder flows onto the chassis. Tin the braid and solder in place.

Here is the location of this mod.

 

[zati]

hello
I'm from France and i'm happy to join this forum and dicuss with others. Then sorry for my bad english, t I don't speak very well english. I 'm used to speak french.
I have a Sansui au 11000 from a long time but recently i have lost the sound of my right amplificator. No more sound come throught the right exit.
What could that be?
Thank's

 

[Ronito6]

I have been meaning to include pictures of the ground mod. Now I have an AU-11000A on the bench so I took some pictures. To recap, there is a screw beneath the front panel that completes the ground path for some of the preamp circuitry. As I recall, if it gets loose you lose audio or the tone controls don't work or something odd like that. To get to the screw you have to remove the front panel. It's smarter and a more reliable fix to simply solder a ground braid from the pc board to the chassis. Here's the location of the screw:

To add the braid, scrape the soldermask off the board and scrape the plating off the inner front panel where shown below:

Now solder a braid to both places. Use a large soldering iron tip or a solder gun but do not overheat the board. Apply solder to the chassis first, using plenty of heat to make sure the solder flows onto the chassis. Tin the braid and solder in place.

Here is the location of this mod.

Truly worth a thousand words.

 

[dr*audio]

hello
I'm from France and i'm happy to join this forum and dicuss with others. Then sorry for my bad english, t I don't speak very well english. I 'm used to speak french.
I have a Sansui au 11000 from a long time but recently i have lost the sound of my right amplificator. No more sound come throught the right exit.
What could that be?
Thank's

The first thing to do is to clean all the controls with a product called De-Oxit. You open the unit up and inject the cleaner into any opening you see in each control, then operate the control 30 times. If that doesn't work, tap on the speaker relay with a non metallic object, like a plastic pen. If the sound comes back or cuts out, replace the relay.