Sansui AU 20000 restoration - many... many pictures

[Kale]

I have been away from that forum for some time, but now I have some interesting pictures to show you... it is about a really big Sansui AU20000 restoration job...

So maybe I will not finish today with posting all pictures, but tomorrow I will... so...

This is the first picture, about what amplifier I am talking here

It is really nice amplifier, but it has a problem, it stays in protection mode...

So my restoration has started with this board:

This is a board where is the main rectifier and where is protection circuit

But at other side of that board, I have found some job from someone in the past, and that job was not nice

So I decided to make one "face lifting" on that board

and the result is

... but it was not only one problem...

... or look at that small signal diode...

 

[Kale]

I had a big problem with that:

below old relay was some mixture which was really hard to clean...

or, that small signal transistor was not original, so I made "undo"

Here they are the main rectifier diodes

 

[Kale]

The next job was on, so called, MotherBoard for Drivers board....
First I have to dismount all those wires

That board was so "greasy" so I have to desolder all connectors and clean them at ultrasonic cleaner

the motherboard is finally out

... after my treatment, it looks now like on that picture:

... and back to its location...

 

[Kale]

... next step was Driver boards and Board with regulated supply

You see, on those boards was something working in the past too...

So let's start with regulated power supply board

these capacitors were changed in the past, I dont know the reason, but I decided to change them all with my favorites capacitors (Elna and Nichicon)

look at that service job

 

[Kale]

But the most interesting thing was this connector

... what... you still dont see... :scratch2:

Ok please take a look at this picture below:

That pin was broken because of corrosion !

The next job was cleaning that glue

And at the end, this is the result

 

[Kale]

Maybe you didnt see one detail on the last picture...
so I am going to show you here

sometime the contact of transistor collector can be lost because that nuts, so I decided to solder them!

 

[Batong]

Great photos and writeup!

 

[ManyMoonsAudio]

Your work is a little better than the last guy.

Those zener diodes are huge!

 

[kevzep]

As always, I am speechless............

VERY nice work Kale!!

 

[Dswankey]

Very cool!!!!, and best of luck getting her back up and running.

 

[24HACKER]

I wish I had half of your talent - beautiful work!!

 

[tobyj17]

Nice job Kale!

 

[Kale]

Thank you guys!

Those zener diodes are huge!

You have the ability to notice details :thmbsp:
Yes, you are right, they are huge, they were 5 watts zeners, but because at that time I didnt have 1 wats zeners, and because the zeners generate much more noise when they work below 40 - 30 % of theirs power, I replaced them with 1 wats zeners when I got them.

 

[Kale]

OK, let's continue with driver boards...

As you can see they have one interesting detail; drivers transistors are different on those two driver board, but they are genuine, and Sansui used the both pairs in theirs amplifiers as driver transistors. But it is interesting what they are not the same pair on the both channels.

... preparing for cleaning connector

... again glue

... what I am going to replace

... in the middle of desoldering job

... glue again

... is it clean now

... what I replaced at those two boards

... and one view below

... and one above

so what I have done until now

 

[aidynphoenix]

:ntwrthy:

 

[Brooklynwgtn]

Wow, very interesting

 

[Curse]

Fantastic work! Most exhaustive

 

[Kale]

I am back... I am glad what you are interested to see my work on that very nice amplifier... so I am going to show you more...

The next step was power stage...

The picture below is final result, but to get that result, you should work really hard...

To dismount the power stage you should remove some wires which goes from TO3 sockets to board...

beside those two pins, you can see the holes which are used for transfer of connections from one side of board to another side. You know, that is double side printed circuit board.
Because of age, those connection can be bad, and because of that you should remove old solder, and put the now one...

Here you can see how it was

Those two screws are not original...

Hm :scratch2: strange... genuine Toshibas beside genuine Sanken

the same on other side...

Now, take a look how it looks like now (the board I mean)

and finally NOS genuine Sankens

TO3 sockets was cleaned by ultrasonic cleaner

 

[Kale]

Dont worry... it is not some broken AU20000 this in only one cleaning fase during my work on that amplifier

... cleaning RCA connectors

... cleaning switch at that board

 

[stereofun]

Kale - you are a master audio restoration craftsman and storyteller.

...and that lead in comment: "...I am going to show you more..." - ranks all the way up there with Prom night, 1987