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Sansui Au-555 strange issue???

Ramaknight

Ramaknight

New Member
Hi all!
I just purchased a Sansui AU-555 which is in beautiful condition physically; the internals have been maintained pretty well and by the looks of the inside its had a good life.
However, I've experienced a strange issue when hooking it up to my system where the left channel has this super aggressive crackling/popping sound when speakers A/B & A+B are selected. I've tried all the selectors, dials to left/right, switches on/off, and have pulled out the main-input links and to no avail.

Video here:

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The guy I purchased it from took it back briefly and experienced some sort of issue with the transistors and has replaced them (UFO + water tower), but the issue persists still. I recently owned/still own an Akai AA-1040 which I cleaned up and performed minor work on, so if its a fairly simple solution such as cleaning/lubing pots/switches I might be able to address this.

Does anyone have any recommendations/suggestions??? Would be greatly appreciated!

Thanks!
 

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quadmatrix82 said:
Replace the 2sc458 transistors with ksc1815 if not already done so a likely culprit
Click to expand...
Thanks! I read all over that those transistors cause common issues - is there an easy way to ID those, I had a little suss inside and most gave the impression of being ‘newer’
 
They're on the pre-amp and tone boards. Those are the boards oriented vertically, attached to the front panel. You'll have to take the front panel off and then the front of the chassis to get enough access to those boards and still there's not a lot of wiggle room on the pre-amp board. Take lots of pictures just in case you accidentally break a wire getting in there. I know that saved me when I did this. They're a little tough to get at but I agree, most likely your problem.
 
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Brian1970 said:
They're on the pre-amp and tone boards. Those are the boards oriented vertically, attached to the front panel. You'll have to take the front panel off and then the front of the chassis to get enough access to those boards and still there's not a lot of wiggle room on the pre-amp board. Take lots of pictures just in case you accidentally break a wire getting in there. I know that saved me when I did this. They're a little tough to get at but I agree, most likely your problem.
Click to expand...
Ah great! I'll have a little suss of these and do some tests. Appreciate it
 
If they're crackling and popping, they may well test fine with the standard multi-meter diode checks or a transistor checker. They're known troublemakers and are known to cause this problem though. There are about 10 of them on those 3 boards as I remember.
 
Yes spot on its best to change them and not leave them to eventually fail and potentially cause other damage too take photos of the wires so you know where they go in case you do break one easy to do on those boards
 
Thank you both for the swift replies! I'm gonna look into ordering some replacements for this beauty and get onto fixing it up :)
 
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