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sansui au-555a amplifier left channel not working


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I have recently bought a sansui au-555a amp and have noticed when it is on stereo mode the left channel is missing certain sounds(instruments/voices). When the amp is switched to mono mode everything works well. Amp is used for its phono output.

If anyone can give me any idea what is causing this problem and how or where to get this fixed I would be very grateful. cheers

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When I first bought it I took it in to a place called speaker bits for a service and they said they would clean out the pots and switches, but when I got it back the whole thing was still covered in dust including the pots, so not sure if they have been cleaned.

It hasn't been recapped yet only because I'm not sure where to get it done, But would like to find someone who does it in the Melbourne area?

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Hi Tim welcome to SNa.

If the amp is fine in mono then your main amplifier section is fine and the problem will be in the preamp stage.

Ortofun is correct in that old amps do suffer from dirty or worn out switches and pots. To test this simply moving your controls around quickly,my guess is the most likely culprit would be the balance control. If it is the problem you can get some electronic contact cleaner from any electronics store.

The next thing to check is swap your left and right interconnects at the back of the amp to see if the problem is before the amp.

Also try swapping to the other phono channel.

If you still have a problem the cost of repair may be more than the amp is worth so the first place to ask for help would be the people in the diy section.

It may also be worthwhile keeping an eye on the classified section for a dedicated phono stage as could be big improvement over the 70s integrated amp.

Best of luck finding the fault.

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i have played around with the knobs and switches and tried both phono channels and even plugged it into the aux channel and still getting the same problem. Just to be clear both speaker channels produce sound on stereo mode just every now and then there will be a missing instrument  normally a guitar or keyboard, and it only happens on some tracks

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I had a similar issue with this AU-555A which I recently restored:

http://www.stereo.net.au/forums/index.php?/topic/82772-fs-syd-restored-sansui-au-555a-integrated-amplifier/

 

Faulty transistors were the cause of the problem.

 

 

 

When I first bought it I took it in to a place called speaker bits for a service and they said they would clean out the pots and switches, but when I got it back the whole thing was still covered in dust including the pots, so not sure if they have been cleaned.

It hasn't been recapped yet only because I'm not sure where to get it done, But would like to find someone who does it in the Melbourne area?

Well that guy Pete above is very good at restoring these, as is his dad Skippy (John) those two guys are highly recommended.....they bleed Sansui when cut :cool:

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@timt8821  best to do this kind of discussion in private, just PM Pete and chat there. Do you know how to send a PM? Hover your cursor over Pete's avatar/name and you'll see the 'send  message' box, click that and your away.

Edited by Luc
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  • 8 years later...

Hi, - I have the same problem. The transistors in the left channel are no good. The flying saucers are 2sc1111, and the others look like Sanyo brand unfortunately indiscernible so cannot identify. What would be the best transistors to use?

In mono, the sound is so smooth, almost tube-like. Sure would love to get the other one going; looking forward to hearing it work in stereo!

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39 minutes ago, argenta said:

Hi, - I have the same problem. The transistors in the left channel are no good. The flying saucers are 2sc1111, and the others look like Sanyo brand unfortunately indiscernible so cannot identify. What would be the best transistors to use?

In mono, the sound is so smooth, almost tube-like. Sure would love to get the other one going; looking forward to hearing it work in stereo!

@pete_mac

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On 22/02/2024 at 9:18 PM, Luc said:

 

It's been a while since I worked on one of these suckers, and most of my audio tweaking gear is still packed away after moving house. My brain is a little foggy on the details.

 

@argenta I'd suggest consulting this thread on audiokarma - the leestereo restorations/upgrades are the 'gold standard' for restoring and enhancing vintage Sansuis:  Leestereo's Restoration/Upgrade of a Sansui AU-555A | Audiokarma Home Audio Stereo Discussion Forums

Edited by pete_mac
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