• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

AU-719 on the bench

ConradH said:
People blame the shrinkage on heat but I've never been convinced. I've seen it on parts that are perfectly fine and have never been subjected to unusual heat, unless it was during shipping. The stuff is shrink tubing after all, so if it was a tad short to begin with it could easily move down over the years. It's even possible that, in a large batch of caps, you just get a few like that right from the factory. Or, some terrible thing could have happened that I've not thought of! Bottom line is, AFAIK, I've never tested a cap with short shrink and found a problem. That's not to say the unit isn't ready for a complete rebuild. :D
Click to expand...

I’ve seen this randomly in older electronics, from industrial equipment to our beloved hiking gear.
I think they came from the factory like this.
 
LWB said:
I just received an order from Mouser and it took two days to get to shipping. Must be having covid issues... All in all, I can't say that I mind the short delay.
Click to expand...

You’re not the only one!
I placed orders at Mouser and Digikey on March 4.
Mouser MAY ship today-Digikey’s website has NO indication when they’ll ship.
 
Well, I got the re-wound transformer back from repair today. It looked OK but it did have one slightly bent screw, and the soldering job on the electrostatic screen wasn't as neat as the original however, overall it looks like a competent job.

One small issue was that the mounting screws had been re-installed the wrong way round meaning that if I mounted it like that it would have been upside-down. I found I couldn't loosen the nuts securing the screws as there was varnish in the threads. So I painted a bit of 'paint and varnish remover' on the threads and waited 15 minutes and the nuts came off easily, and were swapped round to match the other transformer. So with the hardware fixing issues resolved I began testing the transformer.
First was a Primary and then Secondary resistance check - all OK, then a Secondary voltage check - first on DBT (you never know :angel:) all OK - then a full mains voltage check again OK - just over 95V AC (or 47.5-0-47.5) across the whole Secondary winding = good.

Then I re-mounted the transformer in the amplifier and began the re-wiring. I reversed the transformer secondary winding swap, so it is now back to the stock configuration. And with both secondaries disconnected and again via DBT a mains check first with 240V selected - measuring secondary AC voltages - then on full mains - all good. Then a check with 220V selected but 240 VAC input - all good - the expected slightly increased AC voltages from both secondaries. (104V AC)

Then finally, on DBT with 240V selected and 240V applied, with both secondaries connected - all good. Removed the DBT and another check on full mains and we now have +/- 63V DC for both channels. :king:

:beerchug:
 
Hyperion said:
Well, I got the re-wound transformer back from repair today. It looked OK but it did have one slightly bent screw, and the soldering job on the electrostatic screen wasn't as neat as the original however, overall it looks like a competent job.

One small issue was that the mounting screws had been re-installed the wrong way round meaning that if I mounted it like that it would have been upside-down. I found I couldn't loosen the nuts securing the screws as there was varnish in the threads. So I painted a bit of 'paint and varnish remover' on the threads and waited 15 minutes and the nuts came off easily, and were swapped round to match the other transformer. So with the hardware fixing issues resolved I began testing the transformer.
First was a Primary and then Secondary resistance check - all OK, then a Secondary voltage check - first on DBT (you never know :angel:) all OK - then a full mains voltage check again OK - just over 95V AC (or 47.5-0-47.5) across the whole Secondary winding = good.

Then I re-mounted the transformer in the amplifier and began the re-wiring. I reversed the transformer secondary winding swap, so it is now back to the stock configuration. And with both secondaries disconnected and again via DBT a mains check first with 240V selected - measuring secondary AC voltages - then on full mains - all good. Then a check with 220V selected but 240 VAC input - all good - the expected slightly increased AC voltages from both secondaries. (104V AC)

Then finally, on DBT with 240V selected and 240V applied, with both secondaries connected - all good. Removed the DBT and another check on full mains and we now have +/- 63V DC for both channels. :king:

:beerchug:
Click to expand...
:beerchug: I bow :bowdown: to the King :king: :p Now to see how it... :music:
 
Hyperion said:
How does it sound? lets just say now its owner now has an (unrestored) AU-X901 and really likes it, I think his reborn AU-719 will give it a hell of a run for its money. ;)
Click to expand...
He will probably be handing the AU-X901 off to you for a restore sometime soon. Then use it for the front speakers, and the AU-719 for the rear speakers... Oh yeah, now we're talking. :rockon::rockon: :D
 
Well done John. You deserve a big socially distanced hug :hug:. I'll admit I was a little nervous after the transformer guy was so reluctant to take on the job but all's well that ends well.
I can't wait to hear how it sounds. If it can give an X901 a run for its money I will be very impressed indeed.:music::thumbsup:
 
I have just been testing the power output, a test that failed dismally before due to the defective transformer.

The amplifier achieved 125Wpc into 8Ω (spec is 90W) - both channels driven, at the onset of clipping - not bad at all. :thumbsup:
 
Last edited:
I had heard other tales of 719s bench testing well above their rated output. No wonder it killed a 100W rated Uni-Q driver. The AU-x19 series boasted very low distortion figures as a point of differentiaton from their competition and from their own earlier Sansui models. The advertising for the AU-719 was all about its low distortion. Quoting a lower rated output must have helped the distortion figures as they're typically quoted as @ Min rated RMS output.Sansui au-719 brochure 1.jpgSansui au-719 brochure 2.jpgSansui au-719 brochure 3.jpgSansui au-719 brochure 4.jpgSansui au-719 brochure 5.jpg
 
Oh John, you wrapped it for me...Oh boy, did you wrap it. Was that gorilla tape around the bubble wrap ?

Great to catch up with you for a "socially distanced" chin wag this afternoon, talking all things Sansui in the warm spring sunshine.

My first impressions are WOW !!. What a difference. It feels so muscled, athletic, not heavy but fast and powerful across all frequencies. The soundstage is just huge. Eric Clapton's MTV unplugged recording is a good test in my view. If I close my eyes and I can see where every musician is standing and can tune easily into each instrument. It's more analytical, perhaps much more, but the bar has been raised by recently playing the X901. In short, I love it. So many songs I want to hear again. I'm in for a long night. It's almost impossible to play quietly.

upload_2021-3-22_19-23-35.png
 
Hyperion said:
It was good to have a chin wag with you Tony, a very nice spring day for it too. ;)

Glad you like the revitalised and restored AU-719 - my goodness it's been a journey hasn't it, I hope it gives you lots of listening pleasure.
:beerchug:
Click to expand...
:trebon::beerchug:

I've enjoyed every step of the journey with you John. Thanks
 
sansui au719 said:
Oh John, you wrapped it for me...Oh boy, did you wrap it. Was that gorilla tape around the bubble wrap ?

Great to catch up with you for a "socially distanced" chin wag this afternoon, talking all things Sansui in the warm spring sunshine.

My first impressions are WOW !!. What a difference. It feels so muscled, athletic, not heavy but fast and powerful across all frequencies. The soundstage is just huge. Eric Clapton's MTV unplugged recording is a good test in my view. If I close my eyes and I can see where every musician is standing and can tune easily into each instrument. It's more analytical, perhaps much more, but the bar has been raised by recently playing the X901. In short, I love it. So many songs I want to hear again. I'm in for a long night. It's almost impossible to play quietly.

View attachment 2170995
Click to expand...
Really nice to see everything worked out in the end. Also curious what you think from a comparison with the X901.
Enjoy the music!
 
I am glad to see things work out so well. You know, it is said that the AU 719 is not much of an amplifier when compared to the AU 717 and to the topologically different AU 819 and 919 and here we have it being compared to an X balanced 901.

Cheers

Marc
 
mjs1 said:
You know, it is said that the AU 719 is not much of an amplifier when compared to the AU 717 and to the topologically different AU 819 and 919
Click to expand...
I have seen this said a few times. As the 719 is indeed a step forward compared to the 717 in circuit topology I can understand it can be that when the sound of the 717 is your thing the 719 sounds less good. As far as I can see the driver and outputstage of the 719 is similar to the 919 in topology, just less and different output transistors. And in speed a lot closer to the 919.
I could be wrong....
 
You must log in or register to reply here.
Back
Top Bottom