Sansui AU D707 ( AU819 ) on it's way

[frend2001]

The itch got better of me.

It is against all logical submissions but when were we logical in first place. The passion of music reigns over anything but music only.

It's JDM product and is just about to touch Indian shore. Internationally it is renamed as Sansui AU 819. It is one of the last amp from Sansui's golden age.

Since it's a 100v unit a step down transformer is a must. Any pointers here ?

A full recap is planned, Please chime in with your valuable inputs.

Cheers !

Few Pics..

 

[frend2001]

It is supposed to have those dreaded black flag caps. They tend to fail so at least they are going to be addressed even before turning it on.

 

[frend2001]

It's D- Day.

The amp finally arrived today from the land of rising sun.

It was very well packed in double box packaging with more than enough damping.

As FM Prem cautioned the customs charged an arm and a leg as duty but it's worth it.

Ain't it not ?

Thankfully it has Noble polystyrene as place of Black flag caps and the original Sansui exclusive Sanken op transistors in pics.

Since I was hoping to find voltage selector switch inside the amp as found in AU 819 I didn't get stepdown for it.

So no test report till it arrives.

And the amp looks to be untouched. The knobs and switches have a nice tactile feeling to them as well. In fact when I opened the amp up its felt like It's never been opened.

I noticed the corrosive glue under some caps though, but that's for later.

Surprising it's missing all four feet. Curious why ?

Some eye candy....(Before bath pics)

 

[lifewater]

WOW !!

 

[mshifi]

It's D- Day.

The amp finally arrived today from the land of rising sun.

It was very well packed in double box packaging with more than enough damping.

As FM Prem cautioned the customs charged an arm and a leg as duty but it's worth it.

Ain't it not ?

Thankfully it has Noble polystyrene as place of Black flag caps and the original Sansui exclusive Sanken op transistors in pics.

Since I was hoping to find voltage selector switch inside the amp as found in AU 819 I didn't get stepdown for it.

So no test report till it arrives.

And the amp looks to be untouched. The knobs and switches have a nice tactile feeling to them as well. In fact when I opened the amp up its felt like It's never been opened.

I noticed the corrosive glue under some caps though, but that's for later.

Surprising it's missing all four feet. Curious why ?

Some eye candy....(Before bath pics)

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View attachment 38034

Looks similar to the 717

 

[frend2001]

Looks similar to the 717

Yes it does look very similar to AU717 but from inside its much nearer to the 919 lets say almost identical.

In fact 919 has a separate transformer for preamp and additional 20 watts. Other than that not much is different in 919 and 819 (D707).
Ah I forget the space-tech looking oval filter caps of 919.

Have a look

First is 919 and second pic is 819 (D707)

 

[mpasanthosh]

Very nice buy, i would recommend replacing the Black Flags with Silver Micca or C0G Murata capacitors.
It will cost you a bomb if you settle for Silver Micca from Cornell Dublier.
I have my X11, fully restored and recapped by my self, it costed me alot but i am very happy with the end results.
There are no dreaded black flag capacitors not even one, as i have reworked each and every board in the amplifier.

Details can be found in thread https://audiokarma.org/forums/index.php?threads/sansui-au-x11-restoration.788908/.
I have also gain matched pre drivers and replaced all weak transistors in the amplifier, this is something you could do during the restore work.

Where was this amp imported from, interested to know as i cannot find amps in good condition atleast in India.

 

[mshifi]

Internal of 717

 

[frend2001]

Very nice buy, i would recommend replacing the Black Flags with Silver Micca or C0G Murata capacitors.
It will cost you a bomb if you settle for Silver Micca from Cornell Dublier.
I have my X11, fully restored and recapped by my self, it costed me alot but i am very happy with the end results.
There are no dreaded black flag capacitors not even one, as i have reworked each and every board in the amplifier.

Details can be found in thread https://audiokarma.org/forums/index.php?threads/sansui-au-x11-restoration.788908/.
I have also gain matched pre drivers and replaced all weak transistors in the amplifier, this is something you could do during the restore work.

Where was this amp imported from, interested to know as i cannot find amps in good condition atleast in India.

Thanks a lot Santhosh. It means a lot to have guidance from a veteran Sansui afficnado. Please PM your contact no if possible, would love to discuss
many things as I am just noob in this field.

Fortunately this amp does not have dreaded black flags. In this amp Sansui used Noble polystyrene caps so it sweetens the deal and saves a ton of work already. The amp is definitely untouched as felt while opening up the amp.

The amp have Nichicons and ELNAs as factory standard and seem to be in great shape so re-cap is planned for later. Infact when I opened the bottom plate the relays and caps in MC head amp and protection circuit looks like they were put there yesterday.

Although bottom of one of the big filter cap has some seepage around the draining cap which I have to investigate.

And yes there is that corrosive glue. That will be addressed before the first power up.

It was sourced from Japan thru yahoo auction.

Be sharing more pics in due course.

 

[frend2001]

Considering the power factor in equation I have been advised to go for a step down with at least 5 KVA rating.

And it is costing a bomb to make as it's not readily available.

Now this has got me thinking. Is it possible to rewind the primary of inbuilt transformer of this amp to make is accept 220v ?

I can connect to a tech who does rewinding of transformers for his bread n butter.

My concern is..."Is it advisable ?"

So as per the service manual, there is a way without fully rewinding the primary of transformer ?

Please advice.

This is Export model with voltage selector for 100v, 120v, 220v & 240v



and this is Japan model with only 100v.




Thinking aloud, a winding tech can input the line voltage in between the primary winding to make the transformer take 220v.

Is it even possible ?

 

[Hiten]

I guess For modifying original transformer the winding man would calculate turns+gauge and ratio to secondary. Chances are it will need more space. So only expert transformer winder can do it. Not sure though.
What does the manual say about original transformer wattage rating ? I would advice not to tamper original transformer. Make new one with 220 primary (Probably the written wattage on back panel will do) and multitap/s voltages as per schematics. Wait for experienced members to chime in
Regards.

 

[frend2001]

Ok...so no fiddling with tranny,

It turns out a family friend has transformer mfg unit after all.

He straight away ruled out rewinding this tranny, as per him such workmanship is hard to repeat.

Now he's custom making a stepdown from 220v to 100v with power rating of 1Kva with reference to the sansui transformer.

 

[sachu888]

Congratulations the amp seems to be in very good condition.

Regards
Sachin

 

[frend2001]

So here's to the blower cleaning of amp. Some findings :

1. What kind of residue is it ? Flux ? Or some coating. This is bottom of subsonic, loudness n balance control.


https://i.imgur.com/UoUjohw.jpg[/img]']

2. This is the bottom of a suspected filter cap. I think its not seepage but the glue used to stick red and black caps has oxidized or perished and spread all over the caps.

Black electrolyte is ELNA, the can is shipshape no stress signs whatsoever.







3. The mighty transformer of this beast.



4. There is a lot of flux residue on many PCBs. The dirt is greasy. Blowing full form didn't budge it from places.
But there wasn't any dirt whatsoever on boards. All I see is thin layer of dust on top of components and chassis. The underside is clean.

The corrosion spotted earlier was in fact some excess flux which had oxidized and grown hair.

Is it recommend to bath PCBs in IPA ?

 

[Hiten]

It is personal choice but I would suggest not to clean the PCBs. (Just clean with dry brush) Flux does no harm, unless you are looking for internal aesthetics. Check those piggyback leaking capacitors...are they in the schematics ?
Regards
Edit : Just checked on internet. Yes they are in the schematics.

 

[frend2001]

Flux does no harm, unless you are looking for internal aesthetics.

The insides of Amp are super clean. So it will make sense (aesthetically) to clean the residue flux from PCBs.

Also over this long period (we are talking about 40 years old stuff here), maybe somehow the flux has become conductive or god knows what.
So it will bring some peace of mind as well to clean excess flux. The piggyback caps haven't leaked but it sure looks like the glue has spread over the caps.

More closer inspection to follow.

 

[jls001]

Don't bother with the soldering flux residues. And the hot glue that holds the capacitors together is nothing bothersome either. It's a good practice to glue free-standing components but even if they were not glued there's no real harm.

 

[Hiten]

It is debateble but capacitors that are glued to the PCBs are probably to dampen the vibrations. so as not to affect frequency response.
I see this amplifier weighs almost 20Kgs. If you dont mind how much was the shipping cost ?
Thanks and regards.

 

[frend2001]

Yes the glue helps in damping and securing them caps. As this amp is fully direct coupled n has a ultra wide frequency response, it is important to damp all undesired vibrations. So the gluing big caps is engineering choice.

Shipping was 19000 JPY with enforced double box packaging. After fully packed it weighted a hefty 26.5 kgs.

 

[mpasanthosh]

Yes the glue helps in damping and securing them caps. As this amp is fully direct coupled n has a ultra wide frequency response, it is important to damp all undesired vibrations. So the gluing big caps is engineering choice.

Shipping was 19000 JPY with enforced double box packaging. After fully packed it weighted a hefty 26.5 kgs.

I it also good to remove the glue if possible the ones sansui uses are corrosive over period of age.
You can remove it easily but de-solder components before removing it, the glue eats resistor legs easily , and i had to replace few resistors as well.