pete_mac

Sansui AU-999 restoration and enhancement

16 posts in this topic

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

 

 

 

1 person likes this

Share this post


Link to post
Share on other sites

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 :)

Share this post


Link to post
Share on other sites

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'.

Share this post


Link to post
Share on other sites

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

They look great.

Share this post


Link to post
Share on other sites
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

Share this post


Link to post
Share on other sites

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.

Share this post


Link to post
Share on other sites
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

1 person likes this

Share this post


Link to post
Share on other sites

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
4 people like this

Share this post


Link to post
Share on other sites

Nice work so far!!!

 

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

Share this post


Link to post
Share on other sites
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
1 person likes this

Share this post


Link to post
Share on other sites

Magic!

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

Share this post


Link to post
Share on other sites

Great work Pete. Looking forward to your listening impressions.

Share this post


Link to post
Share on other sites
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
1 person likes this

Share this post


Link to post
Share on other sites

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.

1 person likes this

Share this post


Link to post
Share on other sites

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

1 person likes this

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now

  • Recently Browsing   0 members

    No registered users viewing this page.

  • Similar Content

    • By Snapper()
      Item: 1980 Sansui 719
      Location: Melbourne, Bulleen 3105. Travelling to Sydney Monday
      Price: $SOLD
      Item Condition: 7/10 - some defects but this is definitely reflected in the price!
      Reason for selling: Selling everything that isn't being actively used!
      Payment Method: Pickup - Cash, Paypal, COD Only
      Extra Info:
       Sounds as it should. Articulate but grunty. The 719 is the upgrade to the AU-717. it is less 'raw' than the 717, with a more refined top end. Similar build quality, dual transformers and DC/DC coupled. No shortage of information.
      Cosmetically has some defects - but looks pretty good from the front. 
      Operates and sounds as it should with one exception - when powering on for the first time you simply need to flip the switch again. I believe this is related to a very well known issues with these integrateds, but it is by no means a fatal flaw - it just means that it takes an extract 5 seconds to power on. You can buy eBay kits to fix this for (from memory) with instructions for around $US 30. The previous owner said it was like that for the past 20 years he used it!
      This would have to be close to the best sounding amp for $500 you'll find. 
       
      Considering i've had various offers in the low $500 from my gumtree add and here as well I think it's well price, and certainly less than what I paid for it! 
      I *may* be driving to Sydney on Monday for work, but otherwise happy to pack and courier. 
      Pictures:
       
       
       
       
       
       
       
       







    • By CCallil
      Hello all.

      I'm looking for: Sansui 7900.
      Preferably in very good to mint condition, but happy to consider all options. 
      Mainly looking for one that hasn't been altered, all original parts.
      Will pay a good price.

      Cheers.
    • By BrunswickBurt
      Hi all,
       
      I'm after some advice. I have a Sansui SR-20500 turntable run through a Sony TA-1055 amp and floor standing acoustic research speakers.  All bought from Classic Hifi in Sydney 5ish years ago.  It's all old but sounds good, although I now need to replace the stylus (again).
       
      I recently had a chat instore at a shop in Melb and they recommended buy a new cartridge and made a few recommendations. 
       
      I'm now trying to decide whether to buy a new cartridge for ~$250 (Ortofon 2M Red PMP) or buy a new turntable - Rega RP1 Performance for around $570, which has the 2M red cartridge and seems to be well regarded. 
       
      I love my Sansui but it seems that for an extra few hundred dollars it might be better just to upgrade my turntable. Does anyone have experience as to the difference a new cartridge makes to an older turntable? 
       
      Any thoughts?

      Thanks, Dan
       
       
    • By Vintage_Hi_Fi
      Wanted to buy one Sansui au-5500 power switch the toggle kind not push button if you can assist please send me a pm thanks!
    • By Em84
      G'day all
       
      Just asking some questions on behalf of dad, who's Sansui AU-4900 has just started playing up today.
       
      After having it play today, it suddenly cut off and wouldn't come on no matter what we tried. After 30 minutes or so it would turn on but we wouldn't hear the "click" it usually makes, so it looked like it stayed in protection mode possibly.
       
      Then after a longer time period (couple hours) it would start playing fine again and then a quiet "roaring" sound came out of the left speaker and then 20 seconds later the amp cut off again. Speakers are fine (tried with another amp afterwards).
       
      Just a few queries (on behalf of the old man):
       
      1. What could it be ? I know it's best to get a tech to look at it but just an idea.
       
      2. Any recommendations for a Sansui guru that could help fix/service it in Melbourne? I saw some old threads with a couple recommendations but wanted to ask in case there's been any updates in terms of recommended Melbourne Sansui repairers.
       
      3. If it's capacitors that might need replacing, what are the recommended replacements for the AU-4900 capacitors? Or are the originals still available (Panasonics?)
       
      Any advice/recommendations greatly appreciated
       
      Cheers in advance! Sean
       
      @skippy124
      @pete_mac