Another AU717 restoration

[skippy124]

A little while ago I acquired an AU717 to add to the growing collection. The unit was imported from the US as not working, and without a base plate. This was acquired with the intent of restoring it and keeping it for the ever growing Sansui collection. I will add a capacitor list once a full recap has been completed, and also include any other components that were replaced.

I thought I would post up my progress in this endeavour as it may be of some interest and help to AK members.

It was in need of some TLC, as the faceplate and internals will attest.

Top cover was removed, and I think there must have been a half a kilo of dust all over the internals (tone control and equalizer covers also removed)

Close up of one of the main amp modules

Close up of a corner of the Power Supply PCA

The amp suffered some damage during transport, the chassis has been bent slightly where the transformers mount, however that will be taken care of during the restoration

 

[skippy124]

The first thing to do was give the entire unit a basic clean with a small paint brush and vacuum cleaner, and then remove the two main amp modules for a check over, full clean and recap. Usually I will get a non working unit up and running before doing any restoration work, but in this case I decided to do the restoration first

Main amplifier modules removed

The first thing to check are the fuse resistors, as I have indicated in previous threads on Sansui Amps, many have fuse resistors that give problems and should be replaced as a matter of course. Each main amp module has two 150 ohm fuse resistors, and they checked out as follows -

Definitely in need of replacement!!!!

As I was planning to do a full recap and also maintenance work such as removing the glue that was used to secure the larger PCA mounted caps, the amp modules were first stripped down for a clean.

Boards separated from the heat sinks

The output transistors were removed, and the then the transistor mounting bases also removed which allowed the heatsink to be fully separated from the PCA's (with the rear of the PCA's having been cleaned during the process.

Note the heatsink compound, somewhat dry and in need of replacement

The heatsink was then stripped of the mounting brackets, and all everything was given a good clean

 

[skippy124]

The PCA's were also given a good clean, and them the modules were re-assembled

Output transistor sockets remounted

Output transistors placed in position (not yet ready for final assembly, I wanted to check them before putting them back in with new mica insulators and thermal compound

Outputs installed after all tested OK

Next was replacing the fuse resistors,

Existing fuse resistors

New ones in place (taken after the caps were also replaced)

Next on the list of things..... remove caps, remove glue and any affected components and replace caps

 

[skippy124]

The glue used to secure the large caps tends to go hard over time and will affect components that it comes into contact with, fortunately the glue hadn’t damaged any components on the main amp boards

Glue removed

The electrolytic caps were replaced with a mixture of Nichicon HE, Panasonic FC and Panasonic stacked films were used for the 1uf caps.

Next job was to get the power supply board out for inspection

 

[skippy124]

The power supply board was removed and once again the dreaded Sansui glue was evident, and there were quite a few components that had been damaged by contact with the glue

The electrolytic caps were removed, and this revealed the full extent of the problems

The glue had also run down the board in a couple of places, again causing problems with some components it came into contact with

This is the diode pair that was removed in the photo above – note the corrosion

The glue had also run down and around/under one of the fuse clips

Once these components are cleaned they will be re-installed, plus 10 resistors will need to be replaced and all remnants of glue removed. Once this is complete new caps will be installed

 

[skippy124]

The glue has been completely removed (needed to remove another set of fuse clips on the opposite of the board as the glue had run under these as well)

Diode bridge has had the corrosion removed and a cot of clear protective laquer applied.

And the glue around the fuse clips removed

And to show the importance of removing any glue affected components - this rectifier diode is one of several that are spaced off the board with small ceramic tubes, this is what was hidden by one of these spacers and shows the effect the glue can have over time -

The PSU board finally ready for caps to be fitted (there are still two bi-polar caps on the board, I don't have replacements for those at the moment, but a couple are one the way

And the finished result

 

[skippy124]

Whilst waiting on the two bi ploar caps to finish off the power supply board before I can start to put her back together I had a go at the front panel....

Just a reminder of what it originally looked like

Well it wasn't much cleaner behind the front panel either.....

A clean of the panel and the knobs and lever switch covers, and she is back together again

 

[skippy124]

Well, the major part of the rebuild is complete, and she is up and running!!!

My son Pete (pete_mac) dropped in the two bipolar caps that I needed to finish off the power supply board recap, and these were installed and the power supply board refitted to the chassis. I also checked the fuse resistors on the Tone control and Equaliser boards (four 82 ohm fuse resistors on each board), and these were either high in value or open circuit so all were replaced.

Two of the tone control board fuse resistors

Once the power supply board was refitted, the two main amp modules were also put back in and the amp connected via a dim bulb tester to the mains, and power applied. The amp behaved perfectly…. It came out of protection, and preliminary bias and offset checks were done. Bias was a little high on one channel (not surprising given that the amp modules had lots of handling during the restoration and it only takes a slight movement of the adjustment pot to make a big difference in the bias current. The offset was just about perfect. A check of all control showed the balance pot was a little noisy and this was attended to. All other controls were fine. The dim bulb tester was then dispensed with, and final bias and offset checks were made……. It was then time to put the amp through its paces with a test CD that my son Pete burnt for me with a range of different genres, just perfect for this as I know each track pretty well by now…..

Some shots of the final result (pics aren’t particularly good….. black is hard to photograph, particularly indoors with flash.

Before the internal covers were put pack on

Internal covers fitted

Note that the mains transformers are now sitting straight in the chassis

Next on the list of things to do before the restoration is completed is to order four new filter caps, and do a drawing of the base plate in order to get a new one manufactured. Once the filter caps are replaced, and the new bottom cover fitted, I will go through the tone control and equaliser boards and recap those as well. In any case I will continue to update this thread as further progress is made.


Cheers

John

 

[Overundr1]

Very nice John. The 717 is one of my favorite pieces to have on the bench for a rebuild. Sansui goodness for sure.
-Lee

 

[pete_mac]

Looks great Dad! Super-impressed with how this one turned out, particularly as she was so darn dirty to begin with.

The new filter caps, trimmers and the tone/eq boards in future will top it off nicely

 

[skippy124]

Very nice John. The 717 is one of my favorite pieces to have on the bench for a rebuild. Sansui goodness for sure.
-Lee

Thanks Lee,

And I agree, one of my favourite to work on as well. This is the second one I have done, and I have another waiting for a recap. I have also done a 719, and have a couple of 417's waiting as well. The only difficult things in these are the glue removal, and getting access to the power supply board.

I had a little hiccup on this one - I decided to not connect up the main amp modules for the first power up, wanted to check power supply voltages first as this amp was a somewhat unknown quantity. She acted fine on power up... protection clicked of in about 4 seconds, went to measure the +/- 33V rails..... they were at +/- 18V... hmmmm. Had a bit of a look, couldn't see anything obvious, so I decided to do a simulation of the 33V power supply circuit (have been wanting to try out a simulation for a while now)... and it showed that +/-18V was what I should expect. Had a look at the simulation circuit I had drawn... looked right....Had Sansui changed the voltages??? so I cracked open the other 717 I have in for recap.... +/_33V measured.... looked again at the diagram.... and realised that the two grounds for each of the main amp modules (black and white wires) needed to be connected in order to get the correct voltage readings.... Trap for young players..... connected up these and bingo.... voltages were correct.....

Looks great Dad! Super-impressed with how this one turned out, particularly as she was so darn dirty to begin with.

The new filter caps, trimmers and the tone/eq boards in future will top it off nicely

Very happy with the way this came up cosmetically.

Cheers

John

 

[Hyperion]

Superb pics and record of what you did, and how you did it.

I thought I noticed a bent chassis near the transformers in one of your pics :scratch2:

Excellent work John - I like the pic of the rectifier with its lead eaten through

 

[skippy124]

Superb pics and record of what you did, and how you did it.

I thought I noticed a bent chassis near the transformers in one of your pics :scratch2:

Excellent work John - I like the pic of the rectifier with its lead eaten through

Thanks John

That rectifier was a surprise.... I removed them all to check for glue damage.. and that one would not come out after the solder was removed... it broke off easily and left the small lead piece jammed on the PCB hole, had to carefully push it out.

The chassis was bent, the amp had been dropped "upside down" during transit which caused the chassis deformation. If you have a look at the last pic above you will see that the transformers are now straight.

Another funny thing with this unit.... it was untouched except for two of the 2.2uf bypass caps on the main filter caps had been replaced with 0.22uf caps, with the leads not soldered, just wrapped around the filter cap posts. That and finding a loose electro cap floating around inside the unit when it arrived.... haven't been able to find out where it came from as yet, it is a value that is not used in the 717????

Cheers

John

 

[scottrt]

Wow... nice save of a unit that 'literally' looks like it come from the grave! I saw that one on ebay and wondered if all that mess on the faceplate was cleanable. Your brass clackers are bigger than mine.

Scott T.

 

[rasenthiran]

Hi John,

Thanks for the picture and rebuild information.Cant believe how you transformed the ugly face plate to good looking.Did you use any chemical to clean it??

Pete,

I guess this is a very good chance to test your AU-X701 vs AU 719 vs AU 717...

 

[skippy124]

Wow... nice save of a unit that 'literally' looks like it come from the grave! I saw that one on ebay and wondered if all that mess on the faceplate was cleanable. Your brass clackers are bigger than mine.

Scott T.

Hi Scott,

LOL re the clackers!!

I did make some inquiries re the underlying condition of the face plate and knobs (scratches, nicks gouges etc) before pulling the trigger on it, but I wasn't prepared for what was inside

Hi John,

Thanks for the picture and rebuild information.Cant believe how you transformed the ugly face plate to good looking.Did you use any chemical to clean it??

Pete,

I guess this is a very good chance to test your AU-X701 vs AU 719 vs AU 717...

Hi Raj

This particular face plate was just about the worst one I have encountered in over 50 Sansui black face plates..... it has some sort of compound on it, a waxy/oily substance that certainly took some cleaning to remove.... possibly also had some nicotine mixed in although the amp didn't smell and there was no evidence of this anywhere else... just on the front panel, not much on the knobs. I used Windex (non ammonia) for most of the cleaning, and there were a couple of stubborn patches where I used both isopropyl alcohol and acetone (carefully and not where there was any lettering). Once it was clean I gave it a wipe over and rub off with WD40.

Pete and I have some plans for a bit if a shoot out, an this might also include an AUD11 and a BA/CAF1

Cheers

John

 

[Dswankey]

The only difficult things in these are the glue removal.

Cheers

John

BRAVO!!!!!!!!!!

Thank you for posting such great pictures and providing such incisive information of the process. May I ask how you remove the glue? what in particular do you use?

 

[captouch]

Hats off Skippy, awesome job. I really admire and respect the ability of you and others to restore pieces like this. Most would just give up on them and they'd be dump-bound. A great piece of vintage audio saved and less in the landfills.

:tresbon:

 

[Pepa]

Great work John...well documented too :thmbsp:

 

[Dswankey]

Hats off Skippy, awesome job. I really admire and respect the ability of you and others to restore pieces like this. Most would just give up on them and they'd be dump-bound. A great piece of vintage audio saved and less in the landfills.

:tresbon:

Very well said, +1