Jump to content


Photo
- - - - -

Sansui AU-999 restoration and enhancement

Sansui AU999 Nichicon Super Through Silmic II

  • Please log in to reply
15 replies to this topic

#1 pete_mac

pete_mac

    vintage amp fiddler

  • Members
  • 3,203 posts
  • Location: NSW
  • Country: Australia
  • First Name:Pete

Posted 05 April 2013 - 09:37 AM

I'm about to embark on a thorough restoration and re-working of a very clean AU-999 on behalf of a fellow SNAer. :)

 

All of the parts have been acquired, including Nichicon Super Through top-of-the-range filter caps, Elna Silmic IIs for the preamps and signal path locations, Nichicon HEs for the power supply, Nichicon ES for the bipolar caps, some Panasonic ECQV film caps to replace the 1uf electrolytics and below, and some AXON polypropylenes for bypass duties. The troublesome 'flying saucer' transistors will also be replaced with new equivalents.

 

In addition, a bunch of new metal film resistors will find their way into a few critical locations. A few techs on Audiokarma have identified deficiencies in the original preamp circuitry, bass EQ circuit and subsonic filter circuit, and minor mods to these circuits make a tangible improvement in clarity and bass extension, whilst also ensuring that gain levels throughout the amp are better matched.

 

Apologies for the initial crappy photo, as my main camera was misplaced during our recent move.

 

I'll provide ongoing pics of the restoration process, including some pics highlighting the build quality of these older amps. There are several nice touches like prope resistor ladder stepped attenuator controls for the bass, mid and treble, as opposed to standard potentiometers.

 

473e9567-effa-407b-b374-935e5d3c3f56_zps

 

 

 


••• Logitech Squeezebox Touch > Audio-gd NFB3(2014) w/ ES9018, TCXOs and OCC upgrade > restored Sansuis (AU-X701, Sansui AU-719 and AU-7700) > JM Lab/Focal Cobalt 816s speakers > Audio Principe cables •••

#2 A J

A J

    Member

  • Members
  • 3,207 posts
  • Location: NSW

Posted 05 April 2013 - 10:48 AM

Those "Super Throughs" are a work of art - I bought 4X10,000uf for a project that never eventuated. I still take them out of the box and marvel at them though haha - nice choice of components :)


Listening to stereo & stuff............. :)


#3 pete_mac

pete_mac

    vintage amp fiddler

  • Members
  • 3,203 posts
  • Location: NSW
  • Country: Australia
  • First Name:Pete

Posted 05 April 2013 - 10:57 AM

Yeah, they are beasts and very nicely made indeed. I've used the normal 'Gold Tunes' extensively, but this is the first time I've used 'Super Throughs'.


••• Logitech Squeezebox Touch > Audio-gd NFB3(2014) w/ ES9018, TCXOs and OCC upgrade > restored Sansuis (AU-X701, Sansui AU-719 and AU-7700) > JM Lab/Focal Cobalt 816s speakers > Audio Principe cables •••

#4 blinky

blinky

    Member

  • Members
  • 796 posts
  • Location: VIC

Posted 05 April 2013 - 11:27 AM

Ha, SuperThrough, gotta love Japanglish for some odd combos.

They look great.



#5 pete_mac

pete_mac

    vintage amp fiddler

  • Members
  • 3,203 posts
  • Location: NSW
  • Country: Australia
  • First Name:Pete

Posted 05 April 2013 - 11:54 AM

Ha, SuperThrough, gotta love Japanglish for some odd combos.

They look great.

 

Indeed!

 

According to the datasheet, the Super Through offers "the highest tone quality grade by the low drag the gold plating terminal adoption".

 

:love


••• Logitech Squeezebox Touch > Audio-gd NFB3(2014) w/ ES9018, TCXOs and OCC upgrade > restored Sansuis (AU-X701, Sansui AU-719 and AU-7700) > JM Lab/Focal Cobalt 816s speakers > Audio Principe cables •••

#6 skippy124

skippy124

    Vintage doctor

  • Members
  • 1,021 posts
  • Location: NSW
  • Country: Australia
  • First Name:John

Posted 05 April 2013 - 12:21 PM

Will be watching this with interest, particularly the tweaks to the bass response. We will have to have a shoot out with my partially tweaked 999.

#7 blinky

blinky

    Member

  • Members
  • 796 posts
  • Location: VIC

Posted 05 April 2013 - 12:50 PM

Indeed!

 

According to the datasheet, the Super Through offers "the highest tone quality grade by the low drag the gold plating terminal adoption".

 

:love

Wow is the ultimate! Sweet adopting sound for the ear friends! Amplification wonderment for joy and leisure.

(just getting into the spirit of things)

Bill



#8 pete_mac

pete_mac

    vintage amp fiddler

  • Members
  • 3,203 posts
  • Location: NSW
  • Country: Australia
  • First Name:Pete

Posted 17 April 2013 - 10:21 PM

A quick update.

Top cover removed:

999recap1_zps45bd7a42.jpg


The resistor ladder networks for various controls are very cool indeed!

999recap2_zps883e2c38.jpg


Many of the boards are mounted vertically and fit inside slots on the chassis, making this amp quite easy to work on.

999recap3_zpsd2173d95.jpg


Original grey Elna caps:

999recap4_zps25659eaf.jpg


New Elna Silmic II caps:

999recap6_zps40376e04.jpg


The caps on several boards looked fine when viewed from above, but when removed from the PCB, there are clear signs of leakage. Three capacitors were found in this condition, and many had seals which had not yet leaked but were in poor condition. This is the reason why you simply cannot judge the condition of vintage gear based upon a cursory glance, as everything looked fine from above. Put simply, any 30+ year old capacitor is simply well past its used by date!

999recap5_zps0d76b8aa.jpg

999recap7_zps978020b6.jpg


Nichicon HE caps fitted in power supply locations:

999recap8_zpsee3c90b5.jpg

999recap9_zps932e1c23.jpg


One of the original filter caps in-situ:

999recap10_zpsb5940c2f.jpg


A comparison of the original Elna cap with the new Nichicon Super Through cap. These are one step up in both voltage and capacitance, and are a direct fit for the original 40mm diameter clamp:

999recap11_zpsda72925a.jpg


Nichicon cap installed:

999recap12_zps9900d989.jpg


Next up are further capacitor replacements, wholesale transistor replacement on several boards to remove all germanium transistors, resistor changes to fix gain issues in the preamp stage, disabling the 'crowbar' protection circuit, modifying the subsonic filter circuit which affects bass response, and the installation of binding posts in place of the original spring-style speaker wire connectors.

In other words... plenty of stuff to be done, but we're getting there!

Watch this space! :)

Edited by pete_mac, 17 April 2013 - 10:56 PM.

••• Logitech Squeezebox Touch > Audio-gd NFB3(2014) w/ ES9018, TCXOs and OCC upgrade > restored Sansuis (AU-X701, Sansui AU-719 and AU-7700) > JM Lab/Focal Cobalt 816s speakers > Audio Principe cables •••

#9 skippy124

skippy124

    Vintage doctor

  • Members
  • 1,021 posts
  • Location: NSW
  • Country: Australia
  • First Name:John

Posted 17 April 2013 - 10:47 PM

Nice work so far!!!

 

Watching with interest, I still have to do a bunch of stuff to my 999.



#10 pete_mac

pete_mac

    vintage amp fiddler

  • Members
  • 3,203 posts
  • Location: NSW
  • Country: Australia
  • First Name:Pete

Posted 21 April 2013 - 10:57 PM

Another update.
 
The subsonic filter and crowbar protection boards have been removed, with the signal-carrying wire which previously connected to the subsonic boards now neatly soldered up to the connecting sockets for the plug-in boards. This removed some surplus wiring. 
 
The removal of these two tagboards has opened up the underside of the amp a bit more. Not quite as much of a rat's nest! ;)
 
au999crowbargone_zpsf972933b.jpg
 
au999subsonicandcrowbar_zps22c577bb.jpg
 
au999subsonicgone_zpsbfb1268c.jpg
 
 
Also... we have binding posts!!  :banana:
 
au999bindingpostsfinished_zps50b63e3d.jp
 
 
How did I get to this point? Well, I had a bag of smallish binding posts which appeared as though they'd screw into the holes left once the original push terminals were unscrewed and removed. I just needed to try and see if my theory held true.
 
The following pic shows one set of binding posts screwed in, and the old set of push connectors to the right hand side. To remove these, we snip off the metal solder tab and remove the fastening screw. This allows the push connector to be slid out completely, leaving us with a hole as shown in the second pic below. The shaft of the binding posts are the same size as the remaining hole, but the thread is slightly larger. This means you need to slowly screw the binding post into the rear panel and apply some gentle force at the same time. The benefit is that the binding posts are rock-solid.
 
au999bindingscrewedin_zps00bdcdec.jpg
 
au999speakerconnectorsremoved_zps5cf33cc
 
 
One set completed! You will note that I've had to use both of the poly bushes on the front of the binding post to space them out enough. Otherwise, the keyed section of the binding post fouls on the hole in the rear panel. I installed binding posts the same way on an AU-101 recently and they look decent enough too.
 
au999bindingfirstlotdone_zps8260f792.jpg
 
 
Old vs new:
 
au999oldvsnewspeakerterminals_zps55c68ca
 
 
I note that the hole which accepts the speaker wire on these new binding posts is quite small - in fact, nigh on identical to the original push connector. The posts are also very close to each other, all but ruling out the use of bulky spade connectors. Banana plugs are the connector of choice.
 
au999bindingcomparisonholes_zps336e5414.
 
 
Fixing nuts and split washers installed, and wiring installed and soldered up. I had to install new wiring for the negative binding posts as the original wire was too short to reuse.
 
au999bindingpostssecured_zps5e3694d9.jpg
 
 
She's slowly getting there! More recapping to be done, along with transistor replacements and also the resistor swaps for the bass and preamp mods.
 
au999day2finished_zps654f3e0c.jpg
 
au999day2finished2_zpsa4c4f9b3.jpg

••• Logitech Squeezebox Touch > Audio-gd NFB3(2014) w/ ES9018, TCXOs and OCC upgrade > restored Sansuis (AU-X701, Sansui AU-719 and AU-7700) > JM Lab/Focal Cobalt 816s speakers > Audio Principe cables •••

#11 Luc

Luc

    Don't pat... he bites.Yeah really.

  • Members
  • 3,647 posts
  • Location: NSW
  • Country: Australia

Posted 22 April 2013 - 05:46 AM

Magic!

Certainly a tight fit with those binding posts. Be great if there was such a thing as offset binding posts wouldn't it.


Line of Fire     fav song and slightly disturbing video.

 

Equipment:  A whole heap of stuff,mostly black. No idea what to do with it. Hit play does it for me.


#12 Gonzalo

Gonzalo

    10+ Post Club

  • Members
  • 43 posts
  • Location: NSW
  • Country: Australia

Posted 24 April 2013 - 09:32 PM

Nice job! looks very tidy :)



#13 lebowski

lebowski

    The Dude abides

  • Members
  • 2,347 posts
  • Location: VIC
  • Country: Australia

Posted 25 April 2013 - 06:05 AM

Great work Pete. Looking forward to your listening impressions.
the Dude abides

#14 pete_mac

pete_mac

    vintage amp fiddler

  • Members
  • 3,203 posts
  • Location: NSW
  • Country: Australia
  • First Name:Pete

Posted 13 May 2013 - 09:03 PM

Ok, she's done!
 
All transistors (apart from the outputs) have been replaced.
 
Kevzep's preamp mods have been undertaken, along with the bass EQ mod and the deletion of the crowbar protection circuit and the subsonic filter circuit. 
 
The bias was set quite low (8mA) and is now set as per the required 28-32mA in the service manual.
 
The result is a very clean and detailed sounding amp, with a really nice tone to it. It has seriously made me reassess my expectations of what the very early Sansui gear is capable of. I hope to have a longer listen during the week.
 
I'm impressed and I hope that the owner will be impressed too! This is now one of the most thoroughly restored and tweaked AU-999s in Australia (if not the world) and one of the best sounding too. 
 
au999boardsfinished_zpsc8fb3123.jpg
 
au999preampmods_zps6de1c3b4.jpg
 
au999phonoboard_zpsb44570b7.jpg
 
au999finishednaked2_zps6ad63ad9.jpg
 
5003fa68-7886-4111-9933-ce65fa60ce66_zps
 
au999finishednaked1_zps179a16d1.jpg
 
au999finishednaked3_zpsb0844351.jpg
 
au999finishedfront_zps3013d7dd.jpg
 
au999finishedrear_zpsa03a001f.jpg

Edited by pete_mac, 13 May 2013 - 09:10 PM.

••• Logitech Squeezebox Touch > Audio-gd NFB3(2014) w/ ES9018, TCXOs and OCC upgrade > restored Sansuis (AU-X701, Sansui AU-719 and AU-7700) > JM Lab/Focal Cobalt 816s speakers > Audio Principe cables •••

#15 soundfan

soundfan

    Member

  • Members
  • 6,194 posts
  • Location: Brisbane, QLD
  • Country: Australia
  • First Name:Chris

Posted 13 May 2013 - 09:30 PM

Fantastic thread and pics.Kudo's to you Pete.
I'm a luddite when it comes to electronics, but your explainations with pictures make the process you go through relatively easy to follow.

One good thing about music. When it hits you, you feel no pain. Bob Marley


#16 pete_mac

pete_mac

    vintage amp fiddler

  • Members
  • 3,203 posts
  • Location: NSW
  • Country: Australia
  • First Name:Pete

Posted 19 May 2013 - 03:51 PM

Thanks mate, I appreciate your comments!

 

Ok, the 999 has a few hours under its belt now, and I've put it through its paces in my main system.

 

She sounds very nice indeed! Compared to my AU-X701 the midrange is more forward, and I believe there's less detail and a less defined sound stage. The bass extension is very good (no doubt helped by the removal of the subsonic filter circuit which is more of of a hindrance than help) and the tweaks to the preamp circuit mean that you can crank the volume right up and avoid the early clipping that plagues the standard 999. The bass EQ mods also mean that you can really rock the house with a few clicks of the bass knob if you are that way inclined. FAR better than the mild original EQ slopes.

 

Overall, it's a very impressive sounding amp and I could very happily have it as my main amp. It's not necessarily better or worse than my AU-719, AU-X701 etc... just 'different'.

 

The 999 is in the foreground and the 701 is giving it the evil eye from behind:

 

au999vs701_zps06b54a33.jpg


••• Logitech Squeezebox Touch > Audio-gd NFB3(2014) w/ ES9018, TCXOs and OCC upgrade > restored Sansuis (AU-X701, Sansui AU-719 and AU-7700) > JM Lab/Focal Cobalt 816s speakers > Audio Principe cables •••