Sansui AU-111 rebuild and need some help - diyAudio
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Old 8th June 2012, 08:50 AM   #1
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Default Sansui AU-111 rebuild and need some help

I have on my hands the earliest version of this tube amp, with a load of unauthorized mods to a great extent. I'm wanting to restore it all to its original state once and for all. The wiring is quite a mess and taking ages to figure what goes where. As of now, the tone control section was completely bypassed.
I managed to find the schematic but find lacking with some details.
Does anyone have a most detailed schematic and I need to know the VR's as to which is volume, balance, bass, treble, etc. These are not stated on any schematics found online.
Any assistance to my plight is greatly appreciated.
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Old 10th June 2012, 02:55 PM   #2
dls123 is offline dls123  Canada
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Hi,
I have rebuilt a few 1000a receivers and recently did an Au-70 integrated. I just looked up the schematic which you may have. The version I just looked at has 6L6GC finals driven by 12ax7,6aq8,12bh7. It appears to have the typical Sansui SS phono stage boards for each channel. The old germanium transistors could be noisy at this point. First try just recapping the phono board electrolytics and see. Sometimes that is all they need. Otherwise you may have to change resistors and transistors. The film caps are usually still dead on, but the 'lytics need to go. The rest of the amp is pretty straightforward although they are usually pretty tight and a bit hard to work on. All the Sansui tube gear has a sort of punchy, bright sound, but great iron. So if you use oil caps on the output tubes and try to make sort of "warm" choices throughout then you will be very happy. K40 oil caps on the output are a really good choice if you can fit them in. Of course you should rebuild the power and bias supplies completely. Use good caps for the voltage doublers. The Panasonics that McShane sells are a good choice. They used a big 4 uF electrolytic in the signal path, same as in the AU70. I just used a 4.7 uF Solens to replace it. It fit. (yes, I know the Solens is not a warm choice). I tried bypassing the tones in the AU70 and to tell you the truth it didn't sound much different. They are a pain to work on, but will sound very good when done if you persevere. I may have the same schematic as you, but if you want it just email me because it exceeds the attachment limit. If it is like the AU70, the volume pot is the first one in the schematic, associated with the 12ax7, 500K. Find the tone defeat switch and follow the schematic and that will tell you with ones are the tone pots....
Good luck!
Don
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Old 10th June 2012, 05:03 PM   #3
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I got a hold of a A111 schematic. The mag. preamp section is different than the 2 BJT circuit found in other tubed Sansui units. This 1 seems to be truly hybrid. I've uploaded a schematic snippet of the mag. preamp section.

I'm a stuck record when it comes to old units with multiple mag. EQ setups. I routinely suggest 1 pair of RCA jacks be hard wired to the mag. preamp that's permanently set to RIAA. IMO, switches in the signal path at mV. levels are NOT a good thing. Make all the other inputs "line" level. Mouser carries inexpensive replacement source selector switches by Lorlin.
Attached Images
File Type: jpg A111 Phono.JPG (59.5 KB, 318 views)
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Eli D.
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Old 10th June 2012, 07:19 PM   #4
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Currently I need to rewire the volume and balance pots correctly. I can't figure which VR assignment on the schematic. The last time I did a trace, 1st pot (500k) if not mistaken, just after the Function switch is a sub volume located at the back panel.
I'm thinking VR7 & 8 is the main volume and next one is Balance. I compared 2 different schematics Earlier & later, the pots differ in resistance value.
Thanks for the response, more info is certainly welcome.
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Old 17th July 2012, 11:19 AM   #5
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Case closed. Amp restored to its original state with bits and pieces of info found in other forums. Nightmare over.
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Old 23rd July 2012, 06:38 PM   #6
TheMooN is offline TheMooN  United Kingdom
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well done CM , I have spent time under the hood with the AU-111 myself and it,s no walk in the park unpicking all those multi component mechanically wound solder points

I for one would be interested in reading a little more about your re-build and of course your impressions of it,s audio performance ?
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Old 25th July 2012, 07:41 AM   #7
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Quote:
Originally Posted by TheMooN View Post
I for one would be interested in reading a little more about your re-build and of course your impressions of it,s audio performance ?
We can take this offline through private messaging.
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Old 28th December 2012, 10:27 PM   #8
TheMooN is offline TheMooN  United Kingdom
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I hope folks won't mind my pulling this one out of the shorts drawer however I am curious as to how matters AU-111 are working out for you CM ?
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Old 7th January 2013, 10:31 AM   #9
TheMooN is offline TheMooN  United Kingdom
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Naturally , It would also be nice to hear about AU-111 user experiences from any and all members
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