• 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

AU-9900 replacement parts recommendations?

thanks for your excellent posts about my question on FG caps....there sure was a lot of good information in them... .!
...I'm currently reading up on how to do bias on the 9900...this link was a puzzle....seems like the trimmers are backwards in the manual and do cause
frustration when setting the bias and dc offset. I also read Dr.Audio's way and it's not totally clear to me as yet....

https://www.audiokarma.org/forums/index.php?threads/sansui-au-9900-bias-help.520954/page-2

thank-you both very much.
 
MacMillan said:
thanks for your excellent posts about my question on FG caps....there sure was a lot of good information in them... .!
...I'm currently reading up on how to do bias on the 9900...this link was a puzzle....seems like the trimmers are backwards in the manual and do cause
frustration when setting the bias and dc offset. I also read Dr.Audio's way and it's not totally clear to me as yet....

https://www.audiokarma.org/forums/index.php?threads/sansui-au-9900-bias-help.520954/page-2

thank-you both very much.
Click to expand...
I just follow the service manual. I have not had a problem setting bias that way.

Dr.Audio seems to be suggesting 40 mA for bias instead of the 50 mA stipulated by the SM, which equals 20 mA using his method. The problem with his method is if you put new Bourns trimmers in, they can only be set with the amp turned upside down, since access to the trim pots is only from the bottom. The original pots have a slot all the way through the trimmer disk, so you could technically turn them from top or bottom. However, it's clear from the configuration of the driver board Sansui's intent was that it be done from the bottom. I'm sure you could do Dr. Audio's method with the amp upside down, but again, I didn't see the need to follow his method.

I replaced the trimmers on my driver board, so I can only set bias from the bottom. I set the bias after all the restoration work, but before I put the filter caps in. I played music through the amp for about a half hour with all the covers on. Then turned it upside down to set the bias, then DC offset. The main issue, as I understand it, is to run the amp long enough to get it up to normal operating temperature. For that you have to have the covers on.
 
Just an update. The amp (and TU-9900!) is playing nicely. I was getting some static on the L channel, but that turned out to be a dirty filter switch. The sound is amazing! The more I listen to it, the more I want to listen more. I've been doing some comparison to my Eight, which had been my standard for comparing all amps/receivers, but I'm now liking the 9900 more. It just seems to handle any type of music I throw at it. With my other amps/receivers, they do well with certain types, but then there'll be something I don't like, or just doesn't sound as good. However, so far the 9900 has been handling them all and shining. The detail is wonderful, excellent channel separation, very clear, the right emphasis on the respective ranges. You have to like an amp that makes you want more and keep turning it up. :music:

It's a little bit sad, but I think the Eight has been dethroned as my favorite amp!

Neither the AU or TU 9900 were difficult to work on (restored the PS on the TU). All of the boards are "plug in" on the AU-9900 and most are easily removed, the tone boards being the most difficult. QRXrestore states on their website it is a difficult amp to work on, but I can't see why. They also state there are no plug-in boards (wrong) and the wiring is a "nightmare." I don't agree, and I only mention this here because at first that description put me off from working on the amp, but after doing my own research, it looked very doable, which I can confirm it is.
 
Hyperion said:
They might have only seen models where the 'Crimp Smasher' has been at work. :rolleyes:
Click to expand...
Good point, John. Maybe that is far more common than I would have thought. :eek:

sanjib said:
There is a nice video (4 parts) of AU9900 restoration on youtube.
Click to expand...
Yes, and I watched those a couple of times before starting mine; however, a few things to be aware of:

1. He never uses a DBT when testing after each board is recapped.
2. He does not replace anything other than e-caps, no transistors, diodes, or trimmers.
3. He does not replace the filter caps.
 
Yes, you are right. The video is very good to have an idea about how to access all boards!
 
sanjib said:
Yes, you are right. The video is very good to have an idea about how to access all boards!
Click to expand...
That's pretty much why I watched them. I didn't pay any attention to the caps he was using, though he gives generic advice on that. Pretty much a "re-cap" rather than a real "restoration."

I see in your signature that you have both AU-9900 and 717. I'm curious if you've compared the sound quality of the two, and if you've noticed differences?
 
I just finished the full restoration of AU-717. It is pretty much following Lee's Stereo thread but also changes some transistors. It is really sounding big! Regarding AU-9900 it has a problem with preamps, one channel is cutting out (main amps are working fine) so I never listened to it well. I will start the restoration of AU-9900 soon and then I can compare.
 
Planning the next step in the restoration, which is upgrading transistors on the F-2580 driver board.

TR05/6 are 2SC1628, and from my searching consensus is clear that replacement is KSC3503.

TR07/8 are 2SA818, here I've seen recommendations for both KSA1381ESTU and KSA1220AYS. Any recommendation on which should be used in this application? I've got KSA1220AYS on hand, but not KSA1381.

I don't know if I need to replace TR15/16, which is 2SC1124. Looks like replacement is KSC2690AYSTU, which I have on hand.

TR17/18 is 2SA706, and replacement I've seen is KSA1381ESTU, which again I don't have, though not seeing that those need to be replaced.

Basically, what I can gather is that TR05/6 and TR07/8 should be replaced as they often go bad according to advice @dr*audio has posted elsewhere, but might not need to do TR15-18?

Any help/advice on these transistor subs would be appreciated! Any diodes need replacing? I've replaced D05/6 on advice of @Hyperion.
 
You only have to replace the transistors that have the Uniwatt style case.
MPSU45.jpg
 
dr*audio said:
You only have to replace the transistors that have the Uniwatt style case.
MPSU45.jpg
Click to expand...
OK, well that would included all of the transistors I mentioned. Heres the listing from the service manual:

Screen Shot 2021-04-12 at 5.47.57 AM.png

I saw multiple posts about the need to replace 2SA818 and 2SC1628, but not necessarily 2SA706 or 2SC1124.

Also, can 2SA818 be replaced with KSA1220AYS, or do I need to use KSA1381ESTU for TR07 and TR08?

Thanks!
 
KeithD said:
I replaced the trimmers on my driver board
Click to expand...

Hi Keith,
Can you recall which suffix 3386 trimpot you used?
And was the adjustment CCW to lower? I'm looking at the 3386V as that matches the originals offset pinout but wanted to cross check with what you used. Thanks
 
AnalogueBen said:
Hi Keith,
Can you recall which suffix 3386 trimpot you used?
And was the adjustment CCW to lower? I'm looking at the 3386V as that matches the originals offset pinout but wanted to cross check with what you used. Thanks
Click to expand...
Hi Ben, here are the parts I used:

Screen Shot 2021-07-24 at 7.08.29 AM.png

I don't recall which direction is increase or decrease, but that's easy to check either on the data sheet or using a DMM.
 
Thanks for posting this Keith,
I'll look at those, the data sheet is a little ambiguous as in it shows that there are indeed different directions, "1 -2 - 3 & 3 - 2 - 1" , though not what that does. I believe it increases resistance, so I'll check my spares and I'll know.

20210724_224228.jpg

How's the 9900 running?
 
Clockwise increases the resistance between 1 & 2, while decreasing the resistance between 2 & 3.

I hope this is shat you’re asking but I suspect not.
 
You must log in or register to reply here.
Back
Top Bottom