Sansui AU-2200 Restore & Recap

[Zeus12]

Hello Audiophiles,

I have been infected with the "Sansui" bug. I am fascinated with their sound and build quality.

I got this little gem and would like to know if anyone has done a restoration and recap on it. It obviously needs a very good cleaning and from the looks of it, perhaps, this unit has been exposed to some type of humid environment. There is evident corrosion, especially on the back of the chassis. From the M.D. number on the back of the faceplate (5110670) I gather it was build in 1976 October 6th and it was the 70th unit. Please correct me if I´m wrong.

The person that I bought it from said that it works O.K., but after 2-3 minutes of ugly noise it "fixes itself". It´s a kind of noise that resembles -- "Wind hitting a microphone" --from both speakers and independently of Selector or Speakers (A/B). Obviously, something is wrong with it so I decided to do a FULL RESTORE on it and not wait for it to "fix" itself.

That way I can practice on a fairly simple amp and then continue with my Sansui 661 to see if I can get rid of the HUM problem.

Anybody has done a recap on it? Is the sound comparable to the AU-2900 for example? I got the AU-2900 last week and I have to say that for the 13 wats or so it is rated, it sounds like a 1000 to my ears. Sounds GREAT!! From what I understand, "a small amp is a fast amp". Besides, I want to start with the entry level models first and then work my way up. This one looks much simpler to work on compared to the 661 for example. For my limited experience of course.

Attaching some pics I took last night of the internals. Can somebody tell my what is that capacitor doing underneath the power board (470mF 50V)? It is glued to the CB with the "Sansui glue" by the way. Is it a "bypass-cap"? What is its function? Apart from the capacitors, what about those Output transistors (STK016)? Never seen that format before.

Cheers!!!

 

[Hyperion]

Is it a "bypass-cap"? What is its function?

It looks original, hard to say what its exact function is without knowing what it is connected to. If it is acting as a 'bypass' or to 'bump up' the value of a topside mounted capacitor you may be able to rationalise it and mount it on the topside. However, if there is no room on top, just replace it exactly as it is.

what about those Output transistors (STK016)? Never seen that format before.

Those are 'Output Modules' containing several transistors on a special printed circuit board. If they are not faulty just be happy and leave them alone, there is nothing to change inside them, If they are faulty you just change the whole module - they can be difficult to source, and some types (there are quite a few) have been counterfeited and sometimes appear for sale on auction sites.

From what I understand, "a small amp is a fast amp".

That's not necessarily true, and isn't true in this case.

As for the fault, this is almost certainly noisy transistors (or diodes), check the type numbers against lists on here of known troublemaker transistors.

Nice little amplifier, Good luck!

 

[Zeus12]

Hello Hyperion,

Big thank you for your nice and easy to understand explanations. Will start my parts list and look for those noisy "trannies", as I have seen them called here--makes me crack up by the way--and the diodes. The "caps" will all go. I will make a paper diagram this time and draw them out, polarities, specs, etc. so I don´t forget one like I did last time.

I have been told not to use the UKW Nichicon series on the PSU board. Any other series? What about series PW? Basically looking for a high temp (105ºC) and low impedance, correct?

The "output modules" I will definitely leave alone. So basically this is a type of "encapsulated transistor" on a CB board? Fairchild invention?

Regarding the "a small amp is a fast amp" part. As I said, I´m still new to this wonderful world. I got it from the book "Good Sound - An uncomplicated guide to choosing and using audio equipment" by Laura Dearborn (1987). On page 120:

Greater power output is less an issue of volume than one of bass extension. Most of an amp´s power is used up by the lower frequencies; therefore, a more powerful amp will be able to take you down further, or at least take you down with less distortion. A 100-watt amp with 3 dB of headroom is generally enough to produce a full range down to 30 cycles. However, if your speakers do not go down this far or your room is too small to support 30 cycles of bass, there is little point in having an amp that will produce it. In fact, it is likely to be a disadvantage as, all other things being equal, a larger amp tends to sound less good than a smaller one. A lower-wattage amp will give you just as much bass--since your speakers and room, not the amp, are the limiting factors here--along with probably better sound.

Is this the sour grapes fable? If you give me a Sansui 9090db (125W) for example and I compare it to a Sansui 661 (20W) and with MY speakers and in my VERY SMALL room, would I like the 9090db more? I guess I will have to find out someday and let my ears be the final judge. I am just starting to develop my mental sound "database" so I have something to compare it to. All I know is that I´m hooked on the "vintage sound". Once you go "vintage", you never go back!!

Cheers!!

 

[Hyperion]

Regarding the "a small amp is a fast amp" part. As I said, I´m still new to this wonderful world. I got it from the book "Good Sound - An uncomplicated guide to choosing and using audio equipment" by Laura Dearborn (1987). On page 120:

I didn't see the exact phrase in that excerpt you posted, but maybe an explanation of what is normally meant by a 'fast' amplifier would be helpful to you. A 'fast' amplifier, to my way of thinking is one with a 'high slew rate' - this is the ability of the output stage to change the voltage on its output as fast as possible. Slew rate is measured in V/µS - (Volts per micro Second), several Sansui amplifiers are capable of 350V/µS (which is VERY fast) - and one or two a bit higher. The idea being that if the amplifier is 'fast' it will instantaneously be able to follow the input signal more accurately, thus causing less distortion.

 

[Zeus12]

Hi Hyperion,

Thanks again for enlightening me. "Slew rate" is a new term and I will put it in my "Audio Notes" folder. I have been reading the old "High Fidelity" magazines from the 1960´s and they explain a lot of these concepts in layman's terms. I am still trying to get the grasp of watts, amps, volts, ohms, etc. I love it when it is explained as an analogy.

For example,
VOLTAGE is like the pressure that pushes water through the hose. It is measured in volts (V).
CURRENT is like the diameter of the hose. The wider it is, the more water will flow through. It is measured in amps (I or A).
RESISTANCE is like sand in the hose that slows down the water flow. It is measured in ohms (R or Ω).

By the way, is the "slew rate" measurement available for all Sansui amps? Is there a database somewhere?

"There is nothing like the acquisition of knowledge for the THIRST for wisdom to increase".
(G. L. Hipkiss)

Love your Groucho Marx quote!!

Cheers!!!

 

[Hyperion]

Is there a database somewhere?

Not that I am aware of, but it is often quoted in sales brochures for the equipment, or on the first page of Sansui Service Manuals.

There is very unlikely to be a quoted figure for the AU-2200, as it was made before 'slew rate' was 'in vogue'

Found this
https://audiokarma.org/forums/index.php?threads/the-fasterst-sansui-amp-known-to-man.18778/

 

[Zeus12]

Greetings fellow audiophiles,

I have embarked on a full recap and so far this is what I have done:

1. To remove the Sansui glue I used Q-tips and acetone. It literally took me a good long hour to do the underside and top of the board. The underside was horrible. There was glue on the top side too, but a lot less and for the big caps only.

2. Changed all caps with Nichicon PW series and for the 1uF I used WIMA.

3. There was a 470 uF 50V cap (a by-pass cap?) under the board which was connected to the C601 big cap (1500mF 50V). The positive lead of the 470 uF cap was attached to the positive lead of the C601 and the negative lead of the 470 uF cap was attached to the NEUTRAL (3rd pin unused) of the C601 cap.

4. Where should I place the replacement 470 uF cap? Should I glue it on the board like it was originally or should I put it somewhere on the chassis?

5. Should I continue with the Tone board or should I power up it now and see how the PSU board came out?

Thanks for all your help so far. I couldn´t have done it without Audiokarma!!

Cheers!!

 

[Zeus12]

Greeting audiophiles,

Sorry, Hyperion I didn´t see your instructions for the underside cap. I took the liberty to slightly modify the place of the cap. Hope it´s OK the way I did it.

Finished the tone board today. Replaced all caps on PSU and Tone board and unfortunately it does the same "static/windy" sound when you first turn it on and after 2-3 minutes IT WORKS GREAT!!! Great clean, effortless and rich SANSUI sound.

I´m so happy at least I got all the caps in right. What am I missing? Could it be the D601 and D602 Diodes? (10DC-1 and 10DC-1R).




Happy New Year!!!

 

[Hyperion]

What am I missing? Could it be the D601 and D602 Diodes? (10DC-1 and 10DC-1R).

Unlikely, much more likely to be transistors, the usual way to find out which one(s) is with a can of freeze spray. Just a 1 second squirt on a bad transistor is enough for it to show the fault - usually - but not always.

(Better hope it isn't the Output Modules )

 

[Zeus12]

Hi Hyperion,

Thank you for your help. Unfortunately, I didn´t see any other transistors in the Service Manual. From what I understand the "Output Modules" (IC01, IC02) the STK-016B, are the only transistors in the entire amp. They are the 2 closed black boxes which you say are difficult to find. So it looks like I had bad luck? Should I start looking for these "outpus modules" on the net?

Cheers!!!

 

[Hyperion]

Well I think before looking for Output Modules, eliminate everything else first. I think I see a zener diode on the PCB in post #8 - down at the bottom (of the view) next to a red capacitor, I would change that first as they can become noisy, a little less of a long shot compared to the rectifiers - note these are dual rectifiers with opposite polarity.

But, I have now had a look at the schematic and I note 4 x BA311 IC's in the pre-amp as well - these are more likely to be the problem. I imagine these are no longer available and I have no idea if there is a substitute - see what you can find out.

 

[Zeus12]

Hi Hyperion,

So glad to see you have "adopted" me. I really appreciate your help.

You are referring to IC01,02 and IC03,04 (BA311(E,F,) on the F-2400 Equalizer, Tone Control Circuit Board.
Didn´t even notice those. OK. So basically, when you hear that "static/windy" noise at the start-up, is because of some "transistor"? In other words, that´s a typical sound which is related to a transistor.

I will see what I can find for the BA311 ICs. So far, for the "output modules", I found these which come from Hong Kong:
https://www.ebay.com/itm/1PCS-STK01...429711?hash=item239c23884f:g:t8gAAOSwcMlf3H1z

Cheers and Happy New Year!!!

 

[Hyperion]

I forgot to ask - do both channels have this static/wind noise?

 

[Zeus12]

Hi Hyperion,

Yes, both channels have it, on all Selectors and independent of volume. Strange how after 2-3 minutes it just disappeared and it became whisper quiet. It sounded so SWEEEEEET!!! Maybe the placebo effect? Maybe I was so happy after my recap?

Cheers!

 

[Hyperion]

Hi Hyperion,

Yes, both channels have it, on all Selectors and independent of volume. Strange how after 2-3 minutes it just disappeared and it became whisper quiet. It sounded so SWEEEEEET!!! Maybe the placebo effect? Maybe I was so happy after my recap?

Cheers!

I'm beginning to think after changing the zener diode, if that doesn't cure it, that you should just live with the noise until you can find a tech who can trace it for you?

What do you think?

 

[Zeus12]

Hi Hyperion,

OK, I will replace the 2 zener diodes D601 and D602 Diodes (10DC-1 and 10DC-1R) first and then try the 4 BA311s
and then try the "output models". Found this site for very cheap BA311´s: https://www.ebay.es/itm/BA311-IC-SIP7-JAPAN/152870333823?hash=item2397c82d7f:g:mLEAAOSw3wVaX6tK

I tried "probing" one of the diodes with a nylon probe stick at the beginning and it seems to me that it does effect the static/windy noise at the beginning. By the way, that´s what I have noticed in the youtube tutorials. Now for the 10DC-1 and 1-R I understand that I will need to combine 2? I should follow this thread? https://audiokarma.org/forums/index.php?threads/10dc-1-and-10dc-1r-sansui-771.863843/

I also bought a desoldering gun The "ZD-8915" desoldering station and I have to say that it was a really enjoyable experience using it. I also got most of the parts from the "D.I.Y." list here on audiokarma.org.

I am willing to learn and put in the time and effort!! Thank you for guiding me.

Cheers!!

 

[Hyperion]

The zener diode(s) is/are the small glass ones - the 10DC1 and 10DC-1R are a pair of dual rectifiers (that are different), to make up a bridge rectifier - you can make up a bridge rectifier with 4 rectifier diodes, providing they are correctly orientated. Ok on the other steps, hoping the stuff you have identified isn't counterfeit rubbish, and that you are happy to spend more money on the AU-2200.

 

[Zeus12]

Hi Hyperion,

Now I am starting to understand what that bridge rectifier is. And that´s why it´s called a bridge, because there are two.

I would really like to get this little gem working 100% if possible. Other than the static windy noise at the beginning, from what I heard, it sounds GREAT!! I know the bigger models of Sansui, obviously, sound fuller and better overall, but I´m also on a learning journey. As I said before, I would like to start with the "small" amps and then work my way up.

Would these 2 options be OK for a replacement of the 10DC-1 and 10DC-1R? I would need 2 of each, total of 4 and follow this thread: https://audiokarma.org/forums/index.php?threads/10dc-1-and-10dc-1r-sansui-771.863843/

https://www.digikey.es/product-detail/en/on-semiconductor/1N4007/1N4007FSCT-ND/965481
https://www.digikey.es/product-detail/en/on-semiconductor/1N4007RLG/1N4007RLGOSTR-ND/918021

Cheers!!

 

[Hyperion]

Would these 2 options be OK for a replacement of the 10DC-1 and 10DC-1R? I would need 2 of each, total of 4 and follow this thread: https://audiokarma.org/forums/index.php?threads/10dc-1-and-10dc-1r-sansui-771.863843/

This is correct - almost.

https://www.digikey.es/product-detail/en/on-semiconductor/1N4007/1N4007FSCT-ND/965481
https://www.digikey.es/product-detail/en/on-semiconductor/1N4007RLG/1N4007RLGOSTR-ND/918021

This is the wrong substitute.

You need four of these.
https://www.digikey.es/product-deta...ision/1N5393-E3-54/1N5393-E3-54GITR-ND/604796

 

[Zeus12]

Hi Hyperion,

Thank you for enlightening me once again!!

Going to take the opportunity and order 10 of the 1N5393-E3/54 diodes and some more parts from DigiKey along with some flux and tools which I cannot find here. Also found this option which looks very good: https://www.sansui-vintage.com/product_info.php?cPath=15_17&products_id=99

By the way, I have an "BSIDE ESR02 Pro" meter and I would like to check the diodes and see if they are OK or not. Should I do it in circuit or better to take them out?

Cheers!!!