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AU-D907 for restoration

ghamilton said:
What is the difference between the 907 and 907 Limited? The limited has a wood case and copper coated metal. But is that all?
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Filter capacitors are upgraded, higher quality driver, regulated powersupply transistors, higher grade outputs, higher grade coupling capacitors, brons baseplate for powersupply, copper plated chassis provides cleaner path for the ground, at least according to Mr. Ishino, one of the engineers. He also claims the Limited sound is what the D907 should have been. Ofcourse this is all relative and subjective.
 
For me the most important about the D907 Limited is that is is the start of Sansui using copperplated chassis's on most of there 907 and some 707 models accept for the models X907 Decade and the first three alpha models (alpha 907/907X/alpha 907 L Extra, you could call this the cheap period). Also the use of more specialised components like the Nichicon Gold low leakage coupling capacitors, on the next model: D907F/X11 the use of specially selected film capacitors and from the F extra the bigger values of polystyrene film capacitors.
The plan is now as I will finish restoring the D707 this week and after that, restoring an AU-D907 G Extra for a customer, to start one D907 Limited for myself. I will make a thread about this to highlight the difference between the standard and Limited D907.
 
GrisPato said:
Filter capacitors are upgraded, higher quality driver, regulated powersupply transistors, higher grade outputs, higher grade coupling capacitors, brons baseplate for powersupply, copper plated chassis provides cleaner path for the ground, at least according to Mr. Ishino, one of the engineers. He also claims the Limited sound is what the D907 should have been. Ofcourse this is all relative and subjective.
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Did you deduce all of that from the flakey transation in the links I posted, or from somewhere else. :D
 
Hyperion said:
Did you deduce all of that from the flakey transation in the links I posted, or from somewhere else
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Hahaha, not so much information there!
No, I have three of them. And read about it on Ishinolab site.
Quotes from the site:
"I wondered if there was something to talk about and if I had left behind in D907. With regard to the flow of dirty components such as ripples on the ground line and electromagnetic noise, it was possible to assume to some extent that it would be better to make the chassis non-ferrous in terms of electrical and sound quality."

"When I listened to it, I felt that the smoothness came out very well while it was powerful, and the elegance that was not often said in D907 came out."

That site is also how I became interested in the D907 G model, which by the way also has the configuration started with the D907F Extra, the different value of filter capacitors.
They have the four 12000 uF (United Chemicon) and then in parallel the four 4700uF ( Hitacon) from the same size ( 40 X 110 ) and I can just guess why they did that. But you see it in a lot of the alpha 907 models.
 
Hi there - great restoration.
I've had troubles with intermittent DC on the outputs of the driver board of my D907. One is stable and the other wildly erratic. I took out both the 2SK129a FETs - one is good the other is fried. I have read a few threads about using 2sk117's or 170's but I'm finding it hard to source them. Are there any other more commonly available options? Cheers
 
Spendor said:
Hi there - great restoration.
I've had troubles with intermittent DC on the outputs of the driver board of my D907. One is stable and the other wildly erratic. I took out both the 2SK129a FETs - one is good the other is fried. I have read a few threads about using 2sk117's or 170's but I'm finding it hard to source them. Are there any other more commonly available options? Cheers
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It is VERY unusual for a 2SK129 to go bad, almost always it is something else causing the problem, (dual diodes?), however here is a link to a thread you might find useful.

https://audiokarma.org/forums/index...3-single-n-jfet-specs-and-replacement.746462/

I have a feeling that sometimes people suspect a 2SK129 and remove it to test, which may damage it either with heat or ESD, and then the 2SK129 really is bad! - a self fulfilling prophecy.
 
Thanks for the link - I had read it when trying to find a solution.
This has been an issue for me for a while. I have taken this FET out before and it tested OK so I assumed the problem was elsewhere. I have spent hours testing other components and replacing near everything on the board but I have finally sorted the problem! The legs of the FET are very close to each other at the body and I discovered under very close inspection with a magnifying glass, that there was some corrosion or buildup between each leg causing a short. It was miniscule and almost impossible to see, but I scraped it away and the FET tested fine again. I've since installed the board, adjusted DC steady at zero and biased to 20mV. Sounds great!
 
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