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problem sansui au-919 channel cutting off

M

magoxy

New Member
Hi All!!

First post here and quite new to hifi forums...

I'm italian and based in Italy, (so sorry for language mistakes or strange way of writing.... thanks ;-) )
I have herited a splendid au-919. Very pround of it, I soon discovered that the left channel has a problem. :-(

Problem:
After a minute of listening, the left channel systematically cuts off (mute).
Switching off, waiting two minutes, turning it on, both channels works for another minute and again left channel cuts off.

Tests:
Tests showed that the problem persists on both A and B system, on headphones either, on phono 1 and thuner inputs (the ones tested), at all volume range, with all selectors (tone, mute, sub,) up and down...

More:
Also, it is necessary to do some cleaning inside the controls as "crickling" (not sure it works in en) is present on every command (volume, input, balance...) when moving or selecting them. (I suppose is dust as it has been stored without using it for some years.)

How to investigate / solutions?
I have been reading hundreds of threds about the au-919 (some of them on this forum) about so many aspects, including general restoration, the oval capacitors rebuild, and various problems...

Got a lot of informations, but till now nothing that can tell me where it might be my problem or how to look for it.

Only one old thread in an italian forum with same problem, but not the solution!! :-((
The man after many attemps finally sold the ampli...

Some of you here, I know are experts of this amp! BTY thanks guys for your posts super interestings!!!

I'm not an electronic geek and I'd love to give the baby onto the proper hands in order to take care... but I haven't discovered yet whom is THE person here where I live... investingating on this,
but in the meanwhile I'd like to understand where might be the problem (if easy I might put my hand on it) and then speak to a technician in order to understand if he can do the job.

Any advise is much appreciated!
 
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Hi, You may want to determine if you can find protection relays inside the amp. You can hear characteristic click after engaging power switch to position. They are usually tagged "Omron" when you look inside. If this is the case then delicately open plastic casing and clean contacts.
 
I think the problem is with the input selection and other switches in the amplifier. Over time these get heavily oxidised and need cleaning with a good quality purpose made switch cleaner - like DeOxit.

Please read the DeOxit sticky, get some DeOxit, and follow the procedures.

DeOxit sticky.
http://www.audiokarma.org/forums/in...diots-guide-to-using-deoxit-revisited.207005/ (The number of times I post that blasted link !)

Welcome to AK ! (please consider placing further postings about Sansui gear in the "Exclusively Sansui" sub forum here on AK ;)).
 
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Hi!

I have to thank you all for your replies! I followed the cleaning instruction, and it "magically" worked! :-)
Too happy for that. Super smile! I have my LPs turning... and a super clean sound coming out !

Doing this job, it has been also the opportunity to learn better the amp system... very good!
I'll now have to clean the other bricks as well!

as for cleaning tool in Italy I've fund this:
http://www.duecielectronic.it
it worked.

thanks again!


Ciao!
 
Hi everybody...

back on the esame post after some time...

update: all worked fine for some time, then the problems started again... same as before but on the other channel :-(...
I could clearly hear crackling when turning the volume pot, and some time after turning it while playeing both channels were restored, and then get cutted again.
So I sad, ok ! It's not well clean enogh. I reopened it, and recleaned the volume pot by sprying inside the small hole there is on the black plastic cover of the volume pot. It worked again for a while...
Then , after some time, BOTH :-(((( channels got mute. But not always! I now play and on day it's working, following day it's not... then back again for some minutes... there is no rule. When turning volume pot, I now don't hear any crackling nor is restoring channels.

The question: Can it be still the volume pot? How to clean it properly without risking to damage it? The volume pot is closed iside that black plastic box. Can I arrive to open it? is it possible to act on the contacts directly instead of just spraying inside?

Thanks for your help.

Have a good sunday!
 
Sorry to hear of the difficulty you are having with your AU-919. It is possible to open up the volume control of an AU-919, but you need to have certain special tools, (a dremel) and a special replacement push-on 'nut', and the mechanical aptitude and skills to do it. This is absolutely NOT a job for a novice, one slip and you can destroy the volume control which is no longer made or available new from anywhere. However I would suggest that your problem may be elsewhere and not actually the volume control itself. Diagnosing and repairing such a fault in an amplifier as complex and sensitive as the AU-919 is quite a difficult job even for a seasoned tech.

I strongly recommend that you seek out a good tech' to work on your AU-919, which is a special amplifier indeed. You really need someone who is 'vintage audio aware' and has the skills to make a proper job of repairing your amplifier.

Perhaps you will get more replies to confirm my analysis, or otherwise make suggestions for how you should proceed.

Good luck with it - it is a really excellent piece of vintage audio heritage, and should be treated with the greatest care.
 
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