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AU-719 on the bench

sansui au719 said:
I'm hoping GrisPato will come back with contact information for the guy who supposedly replaced the power transformers with toroidals in his 719. If that guy found just the thing it may save time.

Thinking about space, it would look much neater but is replacing both with toroidals strictly necessary, as long as both have the same specification ? Would mismatched types of transformers present a problem. ?
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The only possible problem is inductance. But if the windings are 90 degrees out from each other, that shouldn't be a problem.
EDIT: A shielded torroid also isn't much of an inductance issue. But many torroids come only wrapped in clear plastic. They need a metal cover to shield the magnetic field.
 
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sansui au719 said:
I'm hoping GrisPato will come back with contact information for the guy who supposedly replaced the power transformers with toroidals in his 719. If that guy found just the thing it may save time.

Thinking about space, it would look much neater but is replacing both with toroidals strictly necessary, as long as both have the same specification ? Would mismatched types of transformers present a problem. ?
Click to expand...
I reached out to in the hope he kept the transformer (he sells parts off lesser Sansui's online). Butt the buyer took them to. He was going to get it restored in Köln. The restorer from here fitted it with 2 toroid stacked from 160VA. Said that the originals were 130VA. Have no idea if he knows what he's talking about. My opinion is not. He offered the 719 after recap with a fault in the regulated PS and/ or the toneboard because when you switched the toneboard in : no sound. And what this people say then: is something simple you can fix yourself easily, but they couldn't:wtf:.
So I think that's a dead end.
 
GrisPato said:
I reached out to in the hope he kept the transformer (he sells parts off lesser Sansui's online). Butt the buyer took them to. He was going to get it restored in Köln. The restorer from here fitted it with 2 toroid stacked from 160VA. Said that the originals were 130VA. Have no idea if he knows what he's talking about. My opinion is not. He offered the 719 after recap with a fault in the regulated PS and/ or the toneboard because when you switched the toneboard in : no sound. And what this people say then: is something simple you can fix yourself easily, but they couldn't:wtf:.
So I think that's a dead end.
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Yeah, I get a kick out of sellers that say something is an "easy fix", but yet don't (or can't) fix it. :rolleyes: I just keep skipping on by.. :biggrin:
 
GrisPato said:
I reached out to in the hope he kept the transformer (he sells parts off lesser Sansui's online). Butt the buyer took them to. He was going to get it restored in Köln. The restorer from here fitted it with 2 toroid stacked from 160VA. Said that the originals were 130VA. Have no idea if he knows what he's talking about. My opinion is not. He offered the 719 after recap with a fault in the regulated PS and/ or the toneboard because when you switched the toneboard in : no sound. And what this people say then: is something simple you can fix yourself easily, but they couldn't:wtf:.
So I think that's a dead end.
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Thanks anyway. I just wanted to shake every tree to see if a cat might fall out.

I agree the restorer may be full of BS, but he may well have got the idea of using those toroids from a knowledgeable source. if we knew which 160VA toroids he used and where he got them we could at least look at the specs and determine if they're a suitable replacement. Even if they're not suitable, he could still point us towards a company which might sell a compatible replacement. Do you still have his contact information ?
 
I can contact him through the chat function of the "Markplaats.nl" app , I send him a message asking for some additional information about the specs of the transformers how he decided this and what brand-type he used.
I will post here when i get a response
 
Well, I got a response. The seller had a repairman doing the work. I talked with him on the phone just now. Friendly guy, more experienced then I am for sure. Sadly no extra information. With this amplifier the faulty one sat at 60 Volt Ac unloaded, even activated the protection circuit. He just went with output power that I assumed he guessed at 70 watts (is stated 95 w/channel in service manual) times 2 gives 140, round up, get to 160VA. He is convinced that the Sansui transformer are max 110 VA each and old fashioned iron thingies with wires of just 20 awg so can not be something special.
 
GrisPato said:
Well, I got a response. The seller had a repairman doing the work. I talked with him on the phone just now. Friendly guy, more experienced then I am for sure. Sadly no extra information. With this amplifier the faulty one sat at 60 Volt Ac unloaded, even activated the protection circuit. He just went with output power that I assumed he guessed at 70 watts (is stated 95 w/channel in service manual) times 2 gives 140, round up, get to 160VA. He is convinced that the Sansui transformer are max 110 VA each and old fashioned iron thingies with wires of just 20 awg so can not be something special.
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I understand that transformers have been around for about 100 years and these designs could easily be 50+ years old, so I suppose they could be considered old fashioned. They're probably not anything particularly special.

Anyway, thanks for chasing that up. Did he happen to tell you which brand of toroid he used and who he bought them from ? That information might be useful.
 
sansui au719 said:
I understand that transformers have been around for about 100 years and these designs could easily be 50+ years old,
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Transformer "design" is the same as it was 50+ years ago. Coils of wire and an iron frame. ;) The number of turns, and number of secondary windings determines the output voltage vs input voltage, plus secondary lower voltages for newer "standby" systems. The gauge of wire comes into play for the current rating. And all come into play for the final overall physical size. What has changed is redundancy. Newer ones tend to push the envelope to save a few dimes on copper, size, and weight, and don't have the surge rating the very old ones have. That and plastic seems to have permeated the industry.. Not that it's necessarily "bad", but is cheaper and lighter for some things.
 
GrisPato said:
He just went with output power that I assumed he guessed at 70 watts (is stated 95 w/channel in service manual) times 2 gives 140, round up, get to 160VA.
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I think that arithmetic was based on the space available - more like 'what's the highest wattage toroid I can get in the space available'.
Space available = 100mm (comfortable) or 110mm (tight), 100mm toroid = 160watts = that's the one!
 
Hyperion said:
I think that arithmetic was based on the space available - more like 'what's the highest wattage toroid I can get in the space available'.
Space available = 100mm (comfortable) or 110mm (tight), 100mm toroid = 160watts = that's the one!
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Correct, that is what he told me. He had 110 mm, he had to move the PS board a little to get them in. I described it like that because he said clearly that he also did not have more clues about current values and only used that, power values combined with available space.
 
Hyperion said:
Arising from this little nugget, I've had a look around at Toroidal transformers - but the only ones I can find are too big! - there is 100mm of space between the left side and the PSU/Protection PCB (allowing just over 5mm clearance) to squeeze in two toroidals. But I am still in the dark about how much current capacity we need for the transformer secondary winding, I am thinking 4 or 5A. :idea:
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You might need to go for custom made. Also do not forget shielding around it. Although EMI supposed to be minimal from Toroid but it still exists so simple shield will be needed. Also watch for toroids inrush current. 160VA should not give you headache in terms of inrush current but be aware that such issue exists with torrs
 
Thanks for the heads up, at the moment we are investigating replacement from a unit being parted out - if one exists, or the possibility of having the original repaired or completely rewound.

So we are very much on the lookout for an AU-719 EU mains transformer with 0-220-240V primary, and 44-0-44V secondary.
 
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