Sansui AU-555A

[Sticky]

Hi all,

Long time reader, First time poster...

I have a Sansui AU-555A that i have had for about 3 or so years now (That i picked up at a local 2nd hand dealer for $25!), When i first powered it up, it worked fine, apart from some sratching and popping from the volume pot and other knobs, and the power button was a bit dicky, which i fixed. After a few months i developed a nasty pop/crackle/hum and would drop the left channel in and out and sometimes stop altogether. After reading a bunch of threads on here about what components to check/replace, I decided i would get it serviced professionally to give it a proper once over and spruce up. When i got it back, it worked well, minus some minor noise from the speakers when there was no output and the volume turned down, and i lived with that for about 12 months married to some Definitive BP8B's.

Now, It has more left channel issues, and i can only get sound if i run it in mono. I have reread a bunch of the threads i read initially to decide what i want to do, but im hoping to get some concrete facts about what caps/transistors/diodes/resistors and modifications i should be replacing/doing as im a bit conflicted with some of the info i have gathered. None of the main caps have been changed for what i can tell (all still Elna), Sanyo C875E8K are in place of the "flying saucer" transistors, and there appears to be some Nichicon Caps on the small board that sits behind the input selector.

Ive added some pics to give some ideas of what components may have been replaced.

Any help would be greatly appreciated.

Josh

PS: Sorry for the potato phone pics....

 

[Robisme]

So the amp section is fine. Sounds to me like it may be dirty controls. Try cleaning the controls before changing any parts.

Rob

 

[Alienz]

Did the tech that serviced it explain what he actually did? It looks all original to me. Like Rob said though, do a good cleaning of ALL switches and controls first.

 

[Sticky]

Stupidly, i didn't. In the excitement of getting it back, i totally forgot to ask. But he has opened it at the very least (Date stamp and some initials,and he has labeled the channels on the frame around the main board.

I'll have another go at cleaning the controls. Does anyone recommend anything in particular? Will contact cleaner be sufficient? I have a heap of that.

 

[slimecity]

Use deoxit for contact cleaning. Ummmm, He hasn't actually replaced any important transistors by the look of things - if those are new trannies in one of your photos, they are only in the phono board. You still have problematic flying saucer trannies in the poweramp section. You also have the original trimmers which should be replaced. I would personally stop mucking around with this guy and have a crack yourself if you feel confident to do some work on this amp? It would also benefit from a full recap. Clean all your controls first of course. You need to start by doing simple measurements such as DC offset and bias setting to first ensure the amp is running within spec. Also - try posting in the dedicated sansui forum for more specialised advice. If you search the forum here you will also most likely find a full parts list that other users have used to recon their 555A amps.

 

[Sticky]

I will have a go with DeOxit and test DC offset and Bias settings tonight. It looks like 2 of the caps on the Phono board (?) have been replaced with Nichicon caps, but there isn't much else i can tell that has been done. The guy i had do the work usually does good word (I use him to do guitar amps and speaker repairs), But this time around i will do it myself.

I have also posted in the Exclusively Sansui forum, so i can probably close this thread.