AU 9500 service/recap recommendations please

ChrisAZ

Active Member
I have an AU 9500 that just started some crackling out of one channel. I’d like to get it repaired and would consider getting it recapped and any recommended upgrades.

Can anyone recommend a tech who really knows this model? I would consider shipping it if it was necessary.

I’m also looking for recommendations for upgrades if you have any.

I’d also consider working on it myself but would need to be walked through it. Any good tutorials out there? Would you recommend against it for a first project?
 
If you were going to work on this yourself, I'd be looking at fixing the problem before doing a general recap.

Crackling in one channel indicates either dirty controls that need cleaning, or a failing small signal transistor (usually).

If you are going to do this, see Lee's links above, clean all controls/switches/pots with deoxit, register and download the service manual at hifiengine.com, then test the amp by separating the power and pre stages (and using another poweramp and music source) to localise where the problem lies).
 
You might want to give the speaker relay a look. I've experienced what sounds like the same symptoms you are describing. After some trouble shooting and advice from members here on AK, it turned out to be just that. Lots of good suggestions on what to look for. Good luck.
 
If you were going to work on this yourself, I'd be looking at fixing the problem before doing a general recap.
Crackling in one channel indicates either dirty controls that need cleaning, or a failing small signal transistor (usually).
If you are going to do this, see Lee's links above, clean all controls/switches/pots with deoxit, register and download the service manual at hifiengine.com, then test the amp by separating the power and pre stages (and using another poweramp and music source) to localise where the problem lies).
What he said, +2!
If that clears the unwanted noise, the recap can be relatively easily done by a tech, as most of the boards are of the plug in variety and can be removed for easy access.
I’d also consider working on it myself but would need to be walked through it. Any good tutorials out there? Would you recommend against it for a first project?
This amp is one of the easier amps for a noob to work on due to the pull out boards.
 
You might want to give the speaker relay a look. I've experienced what sounds like the same symptoms you are describing. After some trouble shooting and advice from members here on AK, it turned out to be just that. Lots of good suggestions on what to look for. Good luck.
Yesterday I did replacement of speakers relays on my 907 mos limited and this helped. So simple solution to fix the cracks from one of channels which I was experienced about two years
 
These amps are riddled with noisy transistors, the one I had, on the preamp board there were a few transistors 2SC1313 comes to mind....
In my experience, crackling is not caps or relays. Almost always, hissing, crackling and noise is Transistors or diodes....
 
I recently repaired an AU-8500 that had an extremely noisy FET on the preamp board. I believe the AU-9500 uses the same board. Unfortunately it's also the hardest board to access in the amp. That board is also populated with 2SA726 and 2SC1313 transistors. Both of which are known to get noisy.

That said, the first step is to thoroughly clean all the controls. The #1 source of noise and channel dropout are dirty controls. In most cases, just a good cleaning with fix it. As was mentioned earlier, do not start a recap until you find and correct the source of the noise. Replacing the caps will not eliminate your noise.

- Pete
 
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