Sansui AU317 restoration

[skippy124]

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 -

Next a look inside the unit

[skippy124]

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

At least the underside of the amp was clean!!

Next, some initial checks

[skippy124]

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

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

Replaced with 1/2W metal film resistors

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

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

[skippy124]

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

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

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.....

[skippy124]

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

after

A final internal clean was then undertaken

[skippy124]

A front panel clean was then undertaken along with the knobs and toggle switch covers

The end result -

[skippy124]

The rear panel also got some attention

Before

Parts replaced

[skippy124]

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 September 1, 2012 by skippy124

[Batty]

Sweet project and a great job.

[New Sensations]

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

Enjoy your (Sansui) journey.

[RockandorRoll]

Thanks for that. I know nothing of electronics, but seeing the change was brilliant.

Best thread Ive seen on here in awhile

[nk7]

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 September 1, 2012 by nk7

[THOMO]

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.

[A J]

What JD said - simply stunning

[skippy124]

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 September 1, 2012 by skippy124

[Bus_Boy]

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.

[BATMAQN]

Doctor Sansui

Wish I had your skills!!!

Regards

Seb

[Rockman]

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

[nk7]

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.

[letron]

i am trying to restore an au317

your work is very good

thanks for pictures and explainations

[lebowski]

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 July 24, 2014 by lebowski

[pete_mac]

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

[lebowski]

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.

[kaushiknitin]

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 July 26, 2014 by kaushiknitin

[THOMO]

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 July 27, 2014 by THOMO