Sansui AU-X11 Restoration

As I know all defects of stability which in Sansui AU-X1 were eliminated in Sansui AU-X11.

It is possible to replace 2SK129A on 2SK146?
 
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As I know all defects of stability which in Sansui AU-X1 were eliminated in Sansui AU-X11.

It is possible to replace 2SK129A on 2SK146?

Late last year I bought an X11 that had a blown driver board.

Here is a picture.

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So I am not sure if all X1 problems were solved on the X11.

The X11 was sold in Japan only, so any problems were sequestered to the Japanese market.
So any possible complaints or reports of defect remain in 1980s Japan.
 
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What horror.

That in my amplifier not. Diff borrowed assembly 2SK129A. Measured power failure on the ends of the resistor 1K, according to the scheme, at a voltage of 10V. It made 8,68mV. Transistors iyet identical power failure. The problem not in diff to assembly means at me and in what that the friend.
I need to look for a source of instability and emergence of a background.
 
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Update (Restoration work):

I have finally made another final change to the amp which has brought about a vast difference in its performance . I am now running the amp with power amp knobs fully .

The left and right channels produces accurately the exact same voltage with .differences of around 0.001 between then both !

I found the stage shifting vastly between left and right channels depending on the position of the main volume knob control used for preamp section .

At certain positions of the preamp knob the stage would be centered but at a certain position it would skew a little over to the left or the right .

The issue was diagnosed to the main volume knob Alps black beauty pot .
The gang differences between left and right channels were too huge. Ranging between 500ohms to 1 kohms at a certain position .

This was solved by replacing the black beauty pot itself .

I have made the replacement using ALPS RK27 50KAX2.

The replacement is pretty straight forward with soldering work done on the 6 pin outs .
No chasis cutting is required the Alps RK27 is a direct fit .

Note: please get the genuine RK27 there are lots of fakes floating in the market .

So yes the main preamp control potentiometer is readily available and a easy to do job with no chasis/panel cutting .
IMG_20190125_233228.jpg

I will recommend replacing the black beauty pot due to its age and if it has gang differences please replace it without thinking !
Please desolder the pot check for gang differences it is a must , if this gets wrong you might have to fiddle with power level gain knobs to get a balanced sound stage .
When checking for gang differences please check at various degrees of rotation as well .


Measurements and deviations in gang differences of the removed RK40 will be updated shortly .

On a side note few listening impressions:
The amp brings life to instruments and also the vocals , they sing with lots of emotional touch .
I have been enjoying the journey and am very happy with the amp so far .
It sounds very clean probably the metal film upgrades on driver board have their influence .
 
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I will recommend replacing the black beauty pot due to its age and if it has gang differences please replace it without thinking !
Please desolder the pot check for gang differences it is a must , if this gets wrong you might have to fiddle with power level gain knobs to get a balanced sound stage .
When checking for gang differences please check at various degrees of rotation as well .

Did you try to recondition the original pot through disassembly? If so, although the reconditioning evidently failed to yield the desired result...what were the results?
 
Update (Restoration work):

I have finally made another final change to the amp which has brought about a vast difference in its performance . I am now running the amp with power amp knobs fully .

The left and right channels produces accurately the exact same voltage with .differences of around 0.001 between then both !

I found the stage shifting vastly between left and right channels depending on the position of the main volume knob control used for preamp section .

At certain positions of the preamp knob the stage would be centered but at a certain position it would skew a little over to the left or the right .

The issue was diagnosed to the main volume knob Alps black beauty pot .
The gang differences between left and right channels were too huge. Ranging between 500ohms to 1 kohms at a certain position .

This was solved by replacing the black beauty pot itself .

I have made the replacement using ALPS RK27 50KAX2.

The replacement is pretty straight forward with soldering work done on the 6 pin outs .
No chasis cutting is required the Alps RK27 is a direct fit .

Note: please get the genuine RK27 there are lots of fakes floating in the market .

So yes the main preamp control potentiometer is readily available and a easy to do job with no chasis/panel cutting .
View attachment 1399943

I will recommend replacing the black beauty pot due to its age and if it has gang differences please replace it without thinking !
Please desolder the pot check for gang differences it is a must , if this gets wrong you might have to fiddle with power level gain knobs to get a balanced sound stage .
When checking for gang differences please check at various degrees of rotation as well .


Measurements and deviations in gang differences of the removed RK40 will be updated shortly .

On a side note few listening impressions:
The amp brings life to instruments and also the vocals , they sing with lots of emotional touch .
I have been enjoying the journey and am very happy with the amp so far .
It sounds very clean probably the metal film upgrades on driver board have their influence .

Great info.

I've wondered about the linearity of the volume control pot in my X1 so this seems like a good place to ask. When functioning properly, does the Black Beauty (in the X11/X1) normally maintain a flat frequency through out the complete turn or is there a "sweet spot"?
 
Great info.

I've wondered about the linearity of the volume control pot in my X1 so this seems like a good place to ask. When functioning properly, does the Black Beauty (in the X11/X1) normally maintain a flat frequency through out the complete turn or is there a "sweet spot"?

I've taken apart and reassembled both X1 and X11 main volume pots. There are physical differences internally.

The main volume control in the X1 uses fine wires at the tip of the wipers.
The main volume control in the X11, the wiper arm terminates into strips at tip of the wipers.

So as far as the main volume controls goes, I am not sure if an X1 vs X11 are the same enough to compare. (not sure)

BUT Off hand...the X1 main volume control seemed a little more expensive to manufacture than the X11's. If that translates into a difference you can hear I cannot say.
 
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Did you try to recondition the original pot through disassembly? If so, although the reconditioning evidently failed to yield the desired result...what were the results?
No i have not tried to recondition the volume pot, as it has a lock washer that has to be broken, or cut using a dremel tool to remove the entire pot assembly.
Removing the back cover only one gang's resistive taper can be accessed.
I have tried cleaning though but it does help much, i will post the readings on the gang differences when free. I had differences ranging between 500ohms to 1kohm at certain degree's of turn.
This is the main reason why i considered replacing it .

If the locking washer is cut during the removal process we have to use a u shaped washer to lock it back in.

Kale has done this work successfully.
 
Zero at the exit because of transistors in the amplifier of power can drift: 2SA939B; 2SC2071B;
2SA968B; 2SC2238B. Everything not really hunting to vypaivat and check.
There are only they. That on radiators are very well heated. Can because of it and flow?

How it is possible to check transistors regarding constancy of the parameters?
 
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Late last year I bought an X11 that had a blown driver board.

Here is a picture.

index.php


So I am not sure if all X1 problems were solved on the X11.

The X11 was sold in Japan only, so any problems were sequestered to the Japanese market.
So any possible complaints or reports of defect remain in 1980s Japan.

I've said it here and there before, but I think it is worth mentioning again... I'm with Ronito on this. We have to stop this wive's tail that the X11 fixed all of the issues of the X1. Also, I'm not 100% convinced it is a stability issue and nobody has ever truly dug into that either (not saying it's no instability, just dislike stating rumour as fact).

Whether it's stability, blackflags (have yet to see one gone bad), or just transistors or design pushed to the edge, I don't know, but I have six AU-X11 drivers board that look like Ronito's. 3 out of 4 AU-X11s I purchased came with blown driver boards. Let's stop with this "AU-X11 fixed issues of AU-X1" talk. This is not to say nothing was addressed with the update, but I'm 100% convinced the stock AU-X11 has significant chances to explode :)
 
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You suggest not to spend for repair of this amplifier of time and money, it is simple to take it to spare parts? Not to push luck with "bomoby the slowed-down action"?
 
You suggest not to spend for repair of this amplifier of time and money
No, it is well worth spending the money.
it is simple to take it to spare parts?
No need to do that unless one or more of the major parts are either damaged or missing.
Not to push luck with "bomoby the slowed-down action"?
Nothing done during a proper restoration of an X1 or an X11 is intended to 'slow down' these extremely 'fast' amplifiers. All you should be doing is replacing old components, some of which can become progressively more unreliable with age, some sooner than others - that is the nature of Vintage Restoration. ;)
 
The transistor the tester will not show degradation in operating time of the transistor at increase in its temperature.

In this amplifier transistors of a swing work at the raised modes. Japanese the engineer probably specially them was driven into this mode, for improvement of quality of a sound. Transistors are very hot. But over time some of them do not maintain these loadings. We see results on a photo.

On good current-limiting resistors need to be recalculated. That there were no explosions.
 
Turned out to take a situation under control having replaced 2SK129A with LSK389B a little. Zero floats at the exit in limits 20mV DC. Probably not to achieve the best result.

It was not succeeded to find original 2SK389B.
2SK129A took from the rabtayushchy Onkyo amplifier. where 0 at the exit was constant and did not change yes on the tenth shares of mV. It speaks about curve circuitry of Sansui.
 
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I've said it here and there before, but I think it is worth mentioning again... I'm with Ronito on this. We have to stop this wive's tail that the X11 fixed all of the issues of the X1. Also, I'm not 100% convinced it is a stability issue and nobody has ever truly dug into that either (not saying it's no instability, just dislike stating rumour as fact).

Whether it's stability, blackflags (have yet to see one gone bad), or just transistors or design pushed to the edge, I don't know, but I have six AU-X11 drivers board that look like Ronito's. 3 out of 4 AU-X11s I purchased came with blown driver boards. Let's stop with this "AU-X11 fixed issues of AU-X1" talk. This is not to say nothing was addressed with the update, but I'm 100% convinced the stock AU-X11 has significant chances to explode :)

Highly anticipating your working on one. (A bit George RR Martin-ing on the one you started.) ;)
 
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Not constancy of zero at the exit can be because of the sat-down original output transistors? Can them it is worth replacing with MJ15024/MJ15025?
 
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