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Sansui AU317 restoration


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#1 skippy124

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Posted 01 September 2012 - 10:27 AM

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 -


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Next a look inside the unit

#2 skippy124

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Posted 01 September 2012 - 10:30 AM

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

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At least the underside of the amp was clean!!

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Next, some initial checks

#3 skippy124

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Posted 01 September 2012 - 10:44 AM

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

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

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Replaced with 1/2W metal film resistors

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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

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

#4 skippy124

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Posted 01 September 2012 - 11:18 AM

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

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

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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.

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Glue gone

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Main Amp board recapped

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Next was some other tidying up.....

#5 skippy124

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Posted 01 September 2012 - 11:37 AM

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

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after

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A final internal clean was then undertaken

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#6 skippy124

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Posted 01 September 2012 - 11:41 AM

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

The end result -

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#7 skippy124

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Posted 01 September 2012 - 11:45 AM

The rear panel also got some attention

Before

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Parts replaced

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#8 skippy124

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Posted 01 September 2012 - 11:53 AM

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, 01 September 2012 - 11:54 AM.


#9 Batty

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Posted 01 September 2012 - 11:54 AM

Sweet project and a great job.

#10 John H. Darko

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Posted 01 September 2012 - 11:58 AM

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

Enjoy your (Sansui) journey.

Editor/Publisher, Digital Audio Review.  


#11 RockandorRoll

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Posted 01 September 2012 - 12:18 PM

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

Best thread Ive seen on here in awhile

VPI Scout II : Rega Saturn : PS Audio DLIII (Cullen) : Luxman L550AII : VAF I-33

NAD C565BEE : NAD C355BEE  : John Blue JB4

Bel Canto 300iu : John Blue JB3


#12 nk7

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Posted 01 September 2012 - 12:44 PM

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, 01 September 2012 - 12:44 PM.


#13 THOMO

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Posted 01 September 2012 - 12:57 PM

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.
AMPLIFICATION-Supratek Cabernet 300B preamp, Usher R1.5 power,Almarro 318B SET ,Gainclone 3876T,Accuphase E202
SPEAKERS-Sonique Encore SE,Gale 401a.Edgar horns.Toshiba SS 30s.B&W DM70C Various DIY. DIGITAL-Krell KAV300CD.Sony 715.
VINYL-Technics SP10 in custom lead filled curly jarrah THOMO plinth.Jelco 750 E 10.5inch tonearm.Soundsmith Supex 900 Super II MC cartridge,Denon ASU320 step-up,Yaqiin MS22B phono stage.

ABSURDITY-A statement of belief manifestly inconsistent with one's own opinion.....Ambrose Bierce

#14 A J

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Posted 01 September 2012 - 01:08 PM

What JD said - simply stunning

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


#15 skippy124

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Posted 01 September 2012 - 01:12 PM

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, 01 September 2012 - 01:13 PM.


#16 Bus_Boy

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Posted 01 September 2012 - 07:51 PM

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.

#17 BATMAQN

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Posted 02 September 2012 - 11:39 PM

Doctor Sansui

Wish I had your skills!!!

Regards

Seb

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#18 Rockman

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Posted 03 September 2012 - 04:00 AM

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

#19 nk7

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Posted 07 September 2012 - 11:52 AM

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.

#20 letron

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Posted 13 August 2013 - 02:21 AM

i am trying to restore an au317

your work is very good

thanks for pictures and explainations