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WTH is inside my AU-X111 MOS?

Hunleyj said:
Here you go!
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Yep, the resistors which form the virtual ground are indeed of the same usual value, 2 x 6.8K, as in other Alpha / X-Balanced models :thumbsup:

BUuuuT :D I have a strong feeling that this model will be a bit of a surprise, at least on power-supply side....because if you look at below image on the yellow areas, there are 2 white-ish jumpers JP5 & JP6 which seem to connect each of them to another 6.8K resistor located near the outside heatsinks (pink areas). If you can confirm that in both pink areas are indeed 6.8K resistors (most likely connected on one side with those white-ish jumper wires JP5 & JP6), then I think we should have a "real dual-mono" power supply on this model, unlike the vast majority of Alpha integrated amps (details 2 posts above) ;)
In order to confirm this 100% it's enough to disconnect the "power" supply wires (should be near the output mosfet's, where those added Taitsu caps were also connected) from both power-amp modules and check with an ohm-meter between the (+) or the (-) wire on both channels - like between (+)R and (+)L or similar between (-)R and (-)L. If there is no "short" (less than 1 ohm resistance) and (probably) you see ~13.6K on the ohm-meter, then it's for sure "real" dual-mono.

X111MOS_psu.jpg

I'm really glad that finally we got to discover a bit of this old and very rare Sansui model :cool:

Thank you for your time, sir ! :) :beerchug:

Regards
 
In the 'Stock' configuration there are only 2 x 6.8K resistors, and because of the Red/Blue jumpers being in place (connecting both channel supplies), you only need two. However, when you remove the Red/Blue twisted jumpers you need to add another pair of 6.8K resistors to equip the separated/disconnected channel supply with a virtual ground arrangement.

When I did the modification to my '907MR I mounted the extra resistors on the track side of the board as there was no room topside and it was more convenient anyway. I also fitted 4 new 6.8K resistors, discarding the original single pair.
 
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The "why that way" question regarding how Sansui had chosen to make the power supply for the Alpha series integrated amps is in my view only one of the "why" questions related to Sansui overall....unlikely that any of those questions will ever receive any answer other than our assumptions...which can be far enough from the "truth". That's kind of unfortunate maybe, but this is how it is.
For this reason I'm not trying to find answers to "why they did it this way"....I'm just grateful to have the chance now and then to discover more details about their rare and un-documented models - this being one of those cases.

Regards
 
Hyperion said:
I don't think he has it any more, I think it went to another AK member - who has taken ownership and will deal with it in due course.
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:lurk:

I hope a condition of the sale was the new owner documents Part Deux of this saga here - or their own thread :) .
 
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Hyperion said:
I don't think he has it any more, I think it went to another AK member - who has taken ownership and will deal with it in due course.
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JimEGR said:
I hope a condition of the sale was the new owner documents Part Deux of this saga here - or their own thread .
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Well, without any intention of being critic - at least one short comment like "party suspended for now, hopefully resuming soon" could have been made, it doesn't cost a fortune to do so. But, it is what it is.
I hope that we'll be lucky enough to see at some point those power-amp boards pictures, or hopefully maybe more of them. Let's wait and see what time will bring us :idea: If this one leads again nowhere - it won't be a 3rd time offer from my side. :dunno:

Regards
 
Hunleyj said:
Sorry all. Yes, I ended up selling the amp to someone, and I made sure one of the conditions of sale was that @fojica gets the pictures of the boards :). I’ll ask the other user to make a post here so we can continue following the saga.
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Glad to read it stayed in the “AK Family” :). It is certainly your gear to do with as you please, but it’s sweet to know we will maybe see more of how this story plays out. Looking forward to other Sansui threads from you @Hunleyj!
:beerchug:
 
Ok, I'm the guilty party. After some discussion with @Hunleyj, a mutually agreeable transaction was made in which I bought this unit to finish the restoration. It just made it into my bench a couple of days ago (dammit this thing is heavy) and I have only begun to work on removing the remaining epoxy mess, which is slow, painstaking work.

I will, in due course, get the amp modules and other boards out and in the clear for extensive detail photography so that @fojica can hopefully work up a good set of schematics. I'll need to pull all the MOSFETs to test, as it failed the DBT when @Hunleyj tested it, as he previously posted. I have located a trustworthy source for replacement OE MOSFETs (a couple of suppliers, actually) so if any are perished, I'll be replacing them with identical new devices.

Aside from that, despite a phenomenal packing job done before it was sent to me, FedEx managed to damage the glass panel even more (not that it really mattered, it was already destroyed) and I'm missing one small knob, and have another with damaged finish, so will need to find some suitable knobs to replace them. Since it is unlikely I'll find original factory parts, I'm slogging through tons of ebay listings for black anodized knobs to find some with the correct size and look. Have a couple of candidates as possibilities, but haven't pulled the trigger yet on those.

Assuming all else goes well, I'll have the broken glass panel reproduced. I have the skills and resources locally to get that done, but won't bother spending funds on that portion of the job until the amp is proven to be working. I'll probably do some sort of mockup on paper or transparency just for testing purposes until then.

More to come...
 
Sansuiman said:
Ok, I'm the guilty party. After some discussion with @Hunleyj, a mutually agreeable transaction was made in which I bought this unit to finish the restoration. It just made it into my bench a couple of days ago (dammit this thing is heavy) and I have only begun to work on removing the remaining epoxy mess, which is slow, painstaking work.

I will, in due course, get the amp modules and other boards out and in the clear for extensive detail photography so that @fojica can hopefully work up a good set of schematics. I'll need to pull all the MOSFETs to test, as it failed the DBT when @Hunleyj tested it, as he previously posted. I have located a trustworthy source for replacement OE MOSFETs (a couple of suppliers, actually) so if any are perished, I'll be replacing them with identical new devices.

Aside from that, despite a phenomenal packing job done before it was sent to me, FedEx managed to damage the glass panel even more (not that it really mattered, it was already destroyed) and I'm missing one small knob, and have another with damaged finish, so will need to find some suitable knobs to replace them. Since it is unlikely I'll find original factory parts, I'm slogging through tons of ebay listings for black anodized knobs to find some with the correct size and look. Have a couple of candidates as possibilities, but haven't pulled the trigger yet on those.

Assuming all else goes well, I'll have the broken glass panel reproduced. I have the skills and resources locally to get that done, but won't bother spending funds on that portion of the job until the amp is proven to be working. I'll probably do some sort of mockup on paper or transparency just for testing purposes until then.

More to come...
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GAME ON!
 
That is awesome, so glad a real Sansui collector (and AK member) is now caring for such a rare piece. I feel it will be most entertaining to work your way through the restoration as well.
 
Sansuiman said:
I will, in due course, get the amp modules and other boards out and in the clear for extensive detail photography so that @fojica can hopefully work up a good set of schematics.
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I offered to recover the schematic of the power-amp for the AK community and I'm a man of my word - so that is 100% guaranteed as far as I get good-enough pictures. :thumbsup:
Regarding the pictures - just to preserve the resolution and quality of them, you can upload them on some external storage like google drive or mega.nz or anything similar. We can discuss that directly in private if needed.
As my time will allow, I'll try to go for the other boards as well.
Take your time and we'll manage to uncover as much as possible this rare model - I think both (us, AK's and AU-X111 MV) deserve to have the 'hidden diamond' uncovered, polished and put in the spotlight.
We can work out on this thread or you can open another one, as you find it convenient.

Regarding the output MOSFETS (2SK405/2SJ115) - just a word of caution from me: don't buy just 4 pieces if you find 4 broken ones, for example. Because ideally you'll want to match them as best as possible for Vgs - normally the spread of Vgs between MOSFET's is much higher than Vbe between BJT's. So this is why you normally need more of them, to find to closest matches. And, just in case you don't find 100% guaranteed genuine ones, let me know and maybe I can give you a hint ;)

Regards,
Tibi

LE: if I can help with the restoration (troubleshooting), I'll gladly do
 
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@fojica, I'll probably open a new thread once I really get rolling on this. I'll check with you regarding any specific instructions on what you need, but gather high resolution photos of both the component and solder sides of the boards, close enough in size that the foil side can be overlaid to determine the circuit path between components will be useful in your effort.

Understood also on the matching of these MOSFETs. @Kale does have them on hand, and I'll likely contact him for procurement once I know whether I need replacements. Having purchased from him previously, I know he only deals in genuine quality parts. I will inquire with him as to whether he is willing and able to do matching for me. For now, I think my intent will be to leave as many of the original capacitors as possible. Since everything in this unit was very high spec parts, for which current production replacements of equal quality may not even available, I really don't want to do a wholesale recapping if it can be avoided.

For everyone else observing, this is going to be a major project, and I can't promise the progress will take place quickly due to various other professional and personal commitments on my plate But, I will be plugging away at it with the intent of bringing it back to proper condition both operationally and aesthetically. I am of the mindset that wants to do it right, not merely do it fast.

I do have request to make of those reading this thread. If anyone following this saga owns an AU-111MOS Vintage, it would be very helpful to me if I can get some high quality photos of the front panel, including with a ruler placed adjacent to the various legends (either conventional or metric is fine), so that I can properly judge the placement and size of the various legends and other printing on the panel. Only about the left hand 60% of the glass inlay remains, and it has multiple cracks in it which partially obscure the logo, the model name, and the source indicators along the lower edge.

In order to create the most accurate reproduction panel possible, I would like to get precise data on the placement of the various screen printed elements so that I can properly lay them out prior to having a screen printing service create the screens and apply the enamel to the glass.

Another related matter is if anyone has an original factory owners manual from the AU-111MOS Vintage or any other model that was part of the "Vintage" series, I'm going to need a good clean scan of the stylized VINTAGE word mark to incorporate into the production artwork for the panel reproduction. Presently, I have the Sansui logo, and the typeface used for the other legends will not be an issue to reproduce accurately. A sharp, usable copy of that VINTAGE logo, however, is still eluding me.
 
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Sansuiman said:
^ Heh. I think you've rightly earned the title. Just remenber you are in a forum here with guys who have 20+ years collecting and have (as myself) gone a bit overboard with it.
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I’ve often thought about what it must have been like to find some of this gear for a fraction of what it is selling for now, just 5, 10+ years ago. Not to mention the aficionados here who have been collecting and listening to this gear since it was sold new.

I think the value proposition for this gear is still unsurpassed, even at the current market values. Build quality and sound cannot be beat for the price compared to new.

Long Live Sansui Sound.
 
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Sansuiman said:
@fojica, I'll probably open a new thread once I really get rolling on this. I'll check with you regarding any specific instructions on what you need, but gather high resolution photos of both the component and solder sides of the boards, close enough in size that the foil side can be overlaid to determine the circuit path between components will be useful in your effort.
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I'll keep an eye around here for the new thread :thumbsup:
For the schematic recovery part - what I need is good resolution images with the boards, component-side and pcb/traces-side, to match the traces and the components. No need to be the exact same size of images on both sides, with a bit of zoom it's manageable to match them. Focused images are more important here (no blur if possible). Usually resistor values can be read by color-coding, so I think that will not be an issue. What is more tricky there are the caps (depending how their markings are written on them and can be seen, or eventually from which angle) and even more tricky the small transistors because their markings are normally not visible on a top-image (90-degrees) for component side.
But for the "more tricky" items will probably chat a bit when I'll have the base-schematic ready and I may ask specifically for exact positions of caps and transistors, just to put the right values or types on the schematic. Or eventually just to confirm the values / types that are there. I did this before so I will manage in some way, I'm sure about this (here is an example).

Sansuiman said:
Understood also on the matching of these MOSFETs. @Kale does have them on hand, and I'll likely contact him for procurement once I know whether I need replacements. Having purchased from him previously, I know he only deals in genuine quality parts.
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I know Kale also, bought some AU-D11-II boards from him some time ago.

Sansuiman said:
A sharp, usable copy of that VINTAGE logo, however, is still eluding me.
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Maybe that 1990 Vintage Line brochure would be helpful ? -> https://www.hifiengine.com/manual_library/sansui/vintage-line.shtml

Regards,
Tibi
 
@fojica, sounds like a plan. I'll check out that brochure. I also can get the image from the front cover of a service manual from the AUX-1111MOS Vintage (have seen pictures of that one online). May just have to buy a copy myself, if no one here has one to scan.
 
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