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Sansui AU317 restoration


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Hi,

I have just completed a restoration on a Sansui AU317, and I thought I'd share this.

Firstly some information on the AU317.

Sansui bought out the AUX17 series in the late 70's (AU117 through AU517, and AU717). The AU117 through AU317 were "small form factor" and were not a high as the Au417, 517 and 717. The AU217 is rated at 50W per channel, 20hz to 20Khz both channels driven, and the power amp section has a frequency response of DC to 200 Khz. This particular unit was produced in Sept 1978, so it is an early production unit

The 317 was in for a restoration, and was in "original condition". Fortunately there were no major external cosmetic problems apart from a layer of dirt and dust.

As received -

317bc.jpg

317frontbc1.jpg

317frontbc3.jpg

317frontbc4.jpg

Next a look inside the unit

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Cover off, and sure enough this unit was in untouched condition, with no evidence of any previous repairs

317topbc1.jpg

317topbc2.jpg

317vsBC.jpg

At least the underside of the amp was clean!!

317bottom.jpg

Next, some initial checks

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There are a couple of common issues with the 317 (and other amps in the series)

Fuse resistors - Sansui and other amp manufacturers used fuse resistors to provide protection should other components fail. Over time these fuse resistors have proven to be somewhat unreliable, and tend to drift high in value over time. These fuse resistors are one of the major causes of problems in vintage Sansui amps.

In the 317 there are 6 fuse resistors - 4 an the main amp board, and two on the tome control board

Main amp board fuse resistors

317fuseresistor1.jpg

These are 150 ohm resistors, this is the resistance reading of one of them (the others measured anywhere from 250 ohms to 400 ohms)

317fuseresistor.jpg

Replaced with 1/2W metal film resistors

317fuseresistorsreplaced.jpg

The two 68 ohm fuse resistors on the tone control board measured slightly high and were replaced as they will fail at sometime in the future

Another issue common on many vintage amps is dry or cracked solder joints, particularly on components subject to heat stress. There are two power supply regulator transistors (TO220 case) in the 317 that are prone to cracked solder joints

317regulatortransjoints.jpg

A full recap was next on the list....

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First off, To get easy access to the phono/equaliser amp and control tone boards the front panel needs to be removed

317frontpaneloff.jpg

Equaliser/phono amp board recapped (forgot to take pics of the tone control board)

317equaliserrecapped.jpg

Along with the recap of the this board, the differential input pair transistors for each channel were also replaced with low noise gain matched pairs. The initial checks/tests I did showed some pop/crackle/noise in the left channel when the phono input was selected, and some minor noise was evident in the right channel. Replacement of the input pairs fixed this.

The main amp board was next, and the larger caps are secured with glue. Some of the glue Sansui (and other manufacturers) used tends to go corrosive over time, and can damage components that is comes into contact with, so it is imperative that all traces of the glue is removed.

317CapGlue.jpg

Glue gone

317glueremoved.jpg

Main Amp board recapped

317mainboardrecapped.jpg

Next was some other tidying up.....

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The front panel was then reassembled to the chassis, and the output transistors were removed and cleaned along with the mica insulators, and new thermal compound applied. The heatsink was also cleaned at the same time

Before

317outputsbc.jpg

after

317outputscleaned.jpg

A final internal clean was then undertaken

317topac1.jpg

317sideviewafterclean.jpg

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As part of the restoration, the Bias pots were replaced with multi turn pots as this makes the setting of the bias current much easier than with the single turn pots originally fitted. All controls ans switches were cleaned and lubricated, and the DC offset was also checked and adjusted.

A power output test was undertaken, and the amp made 67W per channel @ 1Khz into 8 ohm each channel driven, and 61W per channel with both channels driven. This is a good result considering the 50W min output spec. After the recap, the hum and noise with the phono input selected (inputs shorted) and volume at maximum was reduced by a factor of 3 times compared with the values measured after just the phono input transistors were replaced.

The Unit will be sent to it's new owner shortly, and I hope that he is happy with the work done. I think that it has come up very well, and listening tests have shown that the performance is typcally "Sansui".

This amp should be good for another 30 years!!

Edited by skippy124
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The love that goes into these restorations and your sharing them on here makes the world a better place.

Enjoy your (Sansui) journey.

I am sure I will enjoy my foray into the sansui world. (I am the new owner by the way). This has been a huge help skippy124. I can't wait to hear it!!

Will be matching them up to some Usher S-520s

Edited by nk7
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Skippy,

Thanks for the post.I have one of these awaiting restoration.It works but definitely has distortion in the preamp section and possibly the power amp too.

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Thanks for the comments gents, much appreciated!!

I am sure I will enjoy my foray into the sansui world. (I am the new owner by the way). This has been a huge help skippy124. I can't wait to hear it!!

Will be matching them up to some Usher S-520s

Hi Nik, I hope that you enjoy the 317, it is a great amp and I think it will work well with the Ushers

Skippy,

Thanks for the post.I have one of these awaiting restoration.It works but definitely has distortion in the preamp section and possibly the power amp too.

Hi THOMO,

Check the fuse resistors first, that is the first place I would look. I can post up the fuse resistor location in the tone control amp if that would be of any help, and If you have another amp with pre out/main in jacks you can do some checks to confirm if the distortion is in either the pre amp or main amp sections, or both.

Cheers

John

Edited by skippy124
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NK you did well mate with this amp. Personally i wouldn't have touched it with a pole seeing it on ebay, but only because i don't have the skills required to undertake the level of work skippy has. Now you have an amp that should sound great and will have a line of people waiting if you ever decided to sell it.

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Nice work Skippy, & great to see some of those worthy old amps given a new lease of life & even updated where appropriate as you've done with the differential input pairs.

More power to You!!!!

Cheers, Barry

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Hi Skip. Just received this amp and am very impressed. Firstly, the amp was not as warm as I was expecting but had greater warmth than my previous amps. The body to vocals is finally filled (compared to the two solid state PA amps I had). The brightness of the speakers are now evident though for some reason, though it still isn't annoying/fatiguing. Usher S-520s seem to be integrating slightly better with the sub I have also purchased. I believe I am now content. And also I think I am becoming a sansui fanboy.

Thank you so very much for the restoration/service work, and especially your time. I am definitely impressed and wouldn't like to know how the amp prior to its service would have sounded.

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  • 11 months later...
  • 11 months later...

Great read. I really must get my 317 to you John for service and recap.

EDIT - I still have the SC1330 here with your name on it. Will send them together.

Edited by lebowski
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Well worth doing Mark. I've got a fully restored mint 317 which is the daily-driver on our PC rig.

I've also got a spare set of Nichicon Gold Tune filter caps which fit the 317 nicely. These might just find their way to Dad's place ;)

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well that would be real swell. I know your Dad has plenty of work so I'll book it in over the next couple of days.

Regardless, I think the Nichicon Gold Tunes will be part of the recap, they went into my 717 and that came up a treat.

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Hello John!

I recently acquired an Au317 in India and I use it with Dali concept 6 floorstanders. The combination sound pretty good to me but there is a little issue.

The amplifier starts to sound better after liek 20 minutes of use and after 30-45 minutes of listening it sounds really good with much more details and the bass. This amp had been sort of "recapped" by an experienced by technically not very sound technician in my neighborhood. I have no better option. We dont have peopel who really can understand vintage amps and that too sansui. The power filter caps are still original.

I have read your post about step by step restoration. can you please help me restore this 317 to its specs? probably you have an advise for me. I can send you photos of the inside of tha amp.

regards an dthank you for reading this.

Nitin Kaushik

Edited by kaushiknitin
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Very decent phono stages in these amps.

I think you would have to spend at least $500 on a dedicated phono preamp to get as good sound.So really worth doing up if you have a turntable as a source.

Edited by THOMO
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Yeah Thomo I have a turntable and I use it with this 317. I also use a good DAC with a tube buffer to feed teh amp. The result is astonishing. i am just not sure that teh amp is performing at its 100% quality since its power caps are old. I dont which ones to buy as teh replacement.

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  • 4 years later...
On 01/09/2012 at 11:18 AM, skippy124 said:

 

 

Along with the recap of the this board, the differential input pair transistors for each channel were also replaced with low noise gain matched pairs. The initial checks/tests I did showed some pop/crackle/noise in the left channel when the phono input was selected, and some minor noise was evident in the right channel. Replacement of the input pairs fixed this.

The main amp board was next, and the larger caps are secured with glue. Some of the glue Sansui (and other manufacturers) used tends to go corrosive over time, and can damage components that is comes into contact with, so it is imperative that all traces of the glue is removed.

 

Glue gone

 

Main Amp board recapped

 

Next was some other tidying up.....

Recently fixed very nasty defect crackle both channels of Sansui AU 3900 amp.  The cause is pair transistors TR601 and TR602 of microphone amplifier! Their Crackle was going to the power supply effecting to all circuit. 

 

 

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  • 8 months later...

I ordered a recap kit from bulgaria...  https://www.audio-high-store.com/product/sansui-au-317-upgrade-kit-audio-capacitors/  It's Nichicon Golds and a couple of Nichicon Muses.  I also replaced the fusible? resistors that the good and honorable Skippy took the care to document here and elsewhere. 

 

It took 2 months to get to Melbourne.  Personally I didn't mind, I care that it got here, not how long as I didn't go fancy schmancy with express post  -  didn't have the coin for that let alone paying someone else to do the recap  for me.

 

I soldiered on through last night and then this afternoon and no bangs/kabloeeys/smoke/housefires once I plugged it into the wall and powered on.  Note, I did assemble electronics for 2 years as one of my first jobs, I don't know what to do particularly unless a foreman says "Oi", insert this resistor in this spot on those 100 circuit boards - or more importantly "it can only go this way" - relevent to recapping.  So, no electronics knowledge particularly but my soldering skills are solid.

 

When I first played something through it, it did have a hint of phasing or some unexpected modulation that has now gone, it will be interesting to see if it recurs when I next switch it on.  So, for a test, Pink Floyds Dark side of the moon from my computer via dac as a reference as I know every bit backwards and nuances from playing it on so many different iterations for 40 years (home stereos/cars/radios/computer speakers).  Clearly compared to before the recap, the definition is so much more pronounced and there are more high-mids and highs than what this amp put out before.  I'm a bass player, I didn't mind the eq setting that I was effectively given - I unswervingly leave tone pots on neutral on my guitars and amps and in a rarity I am engaging the tone circuit and pushed the bass up to +4 , but I think it's just stockholm syndrome as I'm used to this particular amp/speakers having a given sound, I'll start dialing it back. to neutral.

 

So, for anyone interested, while matters might change, the recap kits seem legit (and with many reviews if you chase the web, they are notorious for late delivery - but it ultimately does get there).  Matching up modern capacitors isn't necessarily an easy task, hence the kit, there are discrepancies - use the same capacitance but a higher voltage if you don't see the exact same.

 

I can't comment on the 2 big power capacitors.  When I bought the amp, I got the snoogy woogy (otherwise know as the pooky wookikens) to pay for it to be serviced and I got the tech to replace those 2 capacitors.  As a, "while it's open those are the things most likely needing to be replaced" sort of thing.  No issue, he did surgery as getting the pins lined up on a big modern equivalent capacitor doesn't work - though I thought I saw 1 reference to a set of capacitors somewhere that actually do fit.  

 

As the staff commander in charge of general ignorance, if you are an electronics ignoramus but want to do this for "reasons", do it.  My advice, look up every recap thread on the webz, particularly take note of the "remove evil glue" comments.  Get soldering skills first (night school or whatever), it is an easy skill but it is one of those things that needs to be done right.  Get one of those big movable craft magnifying glass thingies.  Get a kit like the one I mentioned earlier - unless you can find someone who can pick the parts for you (and make sure it's quality, a recap is not expensive to do yourself, a recap with quality components still doesn't cost much and just saves you from redoing the exercise for another 30+ years).  Don't document that you left the workbench and made a coffee - but document everything else, capacitors go in 1 way and it would seem that even if you could read a circuit diagram that they aren't necessarily 100% accurate for these machines (according to the web), so use your phone and take pictures/videos, you want to know and remember which direction to put the negative pole into.  You want to remember how to reassemble.  Also - the volume knob requires (I think...) 1/16th allen key to remove, my smallest 1.5mm just doesn't do it, so get the allen key when you order parts and save yourself from whining at the walls that you can't remove the volume knob, the walls don't care.  I put all similar caps together on a piece of paper with sticky tape and wrote a note - coz the writing on small capacitors is so friggin small, I found it the easiest way to be organised.

 

I now have 2 screws left over that I find really annoying and I forgot to plug in the power led.  But Floyds DSOTM and subsequently AC/DC's TNT on vinyl were an improved experience on before and I'm now playing, Wings - at the speed of sound and damn, I'm feeling pretty smug.

 

Actually, I've put the tone on bypass and am happy with it all back to neutral now, the bass is pumping :)

 

Questions to the local electronics gods. 

1.  Are these discrepancies a burn in thing, just similar to buying a new amp, do capacitors need some time to settle down?  

2.  I didn't bother to recap  the microphone board.  Using general ignorances vast powers of assumption, I informed myself that if a microphone isn't plugged in, that the circuit is open rather than closed, so it doesn't matter.  Thoughts?

3.  It was tough getting out some of the capacitors...  I did it by fingers rather than pliers to try and minimise damage to surrounding components, my guitar calloused fingers are sore - serious sore to the degree that I gave up and had my neighbour pull out the last 3 while I periodically melted solder on the other side.   (Never mind the burns from the soldering iron, wiggling some of the buggers out was a nightmare).  Errr...  this is the question part rather than saying ouch (in any event soothed by a cold frothy or 3), some of the circuit trace at the holes lifted away from the board.  It will stay where cold solder tells it to, so it's flat against the board, but is this an issue - will this affect anything or need a fix?

Edited by daniam
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Guest Muon N'

@daniam

 

Pics would be cool, I'm curious what power filter caps got put into it, I usually use Nichicon KG in those applications, and Silmic's or a mix of Silmic's and Cerafine elsewhere.

 

Caps do settle from new, even if some say they do not, give the amp 30 to 50 hours run time and bass should be better and over all things should be a tad smoother.

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6 minutes ago, Muon N' said:

@daniam

 

Pics would be cool, I'm curious what power filter caps got put into it, I usually use Nichicon KG in those applications, and Silmic's or a mix of Silmic's and Cerafine elsewhere.

 

Caps do settle from new, even if some say they do not, give the amp 30 to 50 hours run time and bass should be better and over all things should be a tad smoother.

For the kit (which I ordered, didn't use), it was 1 nichicon gold tone 10000uf 80v.  Either, they forgot to send 2, or you use esp and deduce that you order 2, it's a kit thing, who wants to do numbers of items, just order "power". 

 

This was a photo taken during the journey sometime, pointing at my next target to see polarity.  But the power cap is there, Jamicon 10,000uf 53Vthumbnail?appId=YMailNorrin&downloadWhenThumbnailFails=true&pid=2

 

And a view of it from behind

thumbnail?appId=YMailNorrin&downloadWhenThumbnailFails=true&pid=2

 

Methinks the "get the cap that just fit's in without surgery" option is preferred, but tracking down the one to fit into place would be hard - I'd seen 1 reference only to a cap that fits in my web searches and I've lost it now or I'd mention it in the OP to save someone else some pain.

 

For the record, "pics or it didn't happen".  Here is my finest photography hour  - the detailed view of my recap!  I didn't have any cold and frothy ones in me at that point, a shame my masterpiece is blurry.

thumbnail?appId=YMailNorrin&downloadWhenThumbnailFails=true&pid=3

 

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Guest Muon N'

None of those yahoo pic work for me, you can upload then into the post from your PC (Drag files here to attach, or choose files - is written next to the paper clip at the bottom).

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The one with my finger - had some reason for it...  Shows the new power caps, also a pic with the flip side of the board.

 

The blurry one...  Well, that sadly is my pic of it finished for prosperity - I took it before I imbibed in celebratory frothies.

thumbnail (1).jpg

thumbnail (2).jpg

thumbnail.jpg

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Those phenolic boards can be a bit of a bugger when desoldering. It's very easy to lift pads, as you found out, by applying heat for too long. Best way is to remove as much solder as possible, as quickly as possible, in short bursts. No more than 2 seconds (max) of heat applied per pad, then let them cool off.

 

You need an iron with a big enough tip, that can deliver enough heat to melt the solder quickly. Too small an iron will do more damage. I generally use a sucker to remove the bulk of the solder, then solder wick to clean up the rest.

 

1. Get iron up to heat (check by pushing a piece of solder against the tip face, and it will melt with only a very very slight resistance to your pressure) , then clean the tip and place the face onto the solder pad, applying a small mount of solder to form a heat bridge between the iron tip and the solder pad.

 

2. When you see the solder melt use the sucker to remove as much as you can in one hit, keeping in mind that you don't want the iron on the pad for any more than 2 seconds. Proceed to the next joint and do the same.

 

3. Get some solder wick braid, gently loosen the weave a bit, if it the compact type, and apply a small amount flux to the braid. Again with a freshly cleaned tip, apply a small amount of solder to the iron and quickly press the braid down onto the solder pad with the iron. Again be mindful of no more than 2 seconds on the pad. You may need to repeat this step a couple of times, letting the pad cool between applications, to remove the rest of the solder.

 

4. gently probe the component leads to make sure they are not still attached by solder. If they are, it will usually be on one side of the lead. With your soldering iron tip applied to the component lead only, gently push the lead away from the attached side till it detaches.

 

5. Once you are sure the leads aren't still held by any solder, you can remove the component from the other side.

 

Never try wriggling the component while heating the solder pad. The pad will detach from the board before the solder melts fully.

 

 

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Guest Muon N'

Not a fan of Jamicon capacitors, to put it mildly.

 

Edit: believe me when I say this is coming from a caring space, Jamicon caps are rubbish.

Edited by Muon N'
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Guest Muon N'

ZB is an ex Marantz service manager, and been in the game for years, maybe read what he says about Jamicon Caps.

 

 

 

My own experience is I used them in decoupling positions in the power supply of a little phone stage once, and they made the phono  stage sound like crap, replacing with even Panasonic FC made a huge difference in SQ.

 

My suggestion is to replace those with Nichicon KG.

 

I think the original caps where 10000uf/50v.

 

 

Edited by Muon N'
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Thanks for the feedback, that's how you learn :)

 

I had the iron set to 350c, had to push it up to 370c as the old solder wasn't keen on melting, was using a solder sucker and melting sparingly.  But I'm hazarding a guess that the struggle to get them out was that the legs were cut by the bluntest set of sidecutters in Japanese engineering history, so they ended up a bit on the mashed side and were a reason for the struggle to get them out through the drilled holes, it was the smaller caps that gave up a fight.  But yep, in struggling to remove I ended up too focused on pulling the cap out and probably kept the iron on for too long - I didn't care about overheating a component I was throwing out - but as mentioned too much heat can lift the pads (I didn't know that).

 

And in retrospect, hear the facepalm.  I could have just tried to trim the legs and amputated the mashed bits...  But I've been known to persistently try to push open stubborn doors that are meant to be pulled.  

 

With the Jamicons.  While parts are cheap compared to labour and I wish I was just charged more for better caps...  At the time, I was just happy that it was done and his clean up (and power recapping) made the machine better, which is what you want from a new 2nd hand purchase.  I didn't entertain the notion of doing any of it myself, though, in retrospect I would.

 

Looking at the reengineering that was done on the flip side of the board.  I'm thinking that it's not going to be just a simple case of Jamicon power caps out, new power caps in.  It's currently working and I don't want to "un-make it work", will have to be done by a tech when I get this serviced sometime.

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Guest Muon N'

If you were in Bris' I'd be happy to do the change over for you, just to see them out............ but alas :(

 

Old boards are tricky, and even some new PBC's in recent equipment can be a PITA.

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