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Another AU-9500 with static sound on the left channel!

Ronald.C

Ronald.C

Active Member
So today my Sansui AU-9500 presented the same symptom of some Forum friends.
The left channel when heated, did not notice the problem with it cold, began to make noises that look like the sound of static.
I cleaned all the potentiometers, the left channel driver board and the F2006 board with clean contacts and the noise stopped, after 5 hours listening to the noise returned. What I realized is that the volume does not interfere with the noise, nor any selector switch, the noise continues and only when I turn it off.
When it cools the noise disappears and only comes back when it reaches a certain temperature!
My question is this: Has anyone been able to find out the real culprit in this problem? Or did they all recap the capacitors? I do not have the intention at the moment to change everything, so I would go straight to the source of the problem!
Here in Brazil it is almost impossible to find nichikon capacitors, and buying on Ebay is very expensive because of shipping! So I would like to change as little as possible!
 
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The 9500 is full of problematic transistors which are well-known noise makers (2SA726 and 2SC1313 in particular).

If you have some freeze spray on hand, you could let them amp warm up and when the cracking/static occurs, start to work your way through the amp transistor by transistor and give each a short spray to see which one is causing the noise.

That said, even if it’s only one which is faulty, I’d replace all of those nasty little suckers.
 
kevzep said:
Those transistors outperform the originals substantially.
I would not even give it a second thought, get them in there, get the old ones out.
Click to expand...

That's exactly what I'm going to do !!! Once again thank you very much, you are wonderful people, I wish I could live near you !!!!
 
I left my AU-9500 with an expert Mr. Masaru Isawa and he told me that sansui has not yet made any statica noise! I asked him to let the device warm up a little more!
 
Hi,

Yes, the FBU and FTA relate to how the transistors are supplied. FBU is bulk packed with straight leads, and the FTA is supplied on paper tape with outer leads bent (splayed). This is shown on the data sheets for each transistor

Cheers

John
 
The technician who is repairing my Sansui AU-9500 said that the BC550 and the BC600 would work without problems but would have a certain gain in the oscilloscope. Here in Brazil is not the Ksa992 nor the KSC1845. Actually he is doing tests on the preamplifier board with these BC550 and BC 660, but he asked me if I even want to buy the ksa992 and the KSC1845 to replace all the transistors.
 
These numbers was my technician who said, but I looking at the service manual I have another account: 8-Ksa992 6-KSC1845.
 
Personally I would have bought more than you need, they are very cheap and it's nice to have a few 'spares', otherwise the order looks fine to me.
 
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