Sansui AU-5500 - Recap and Restore

[Zeus12]

Greetings fellow audiophiles,

I´m so in love with this model that as soon as I saw another on for sale, I JUMPED ON IT!! This one is in much better condition than my previous one. Oh, what a learning journey that one was. Got it fully recapped, changed the problematic transistors and it´s working like a charm!!!
https://audiokarma.org/forums/index.php?threads/sansui-au-5500-driver-and-psu-board-recap.987740/

For the 2nd one, I would like to do a full another recap and restore, improving and correcting my previous mistakes. It´s working great now and all parts seem to be 100% original.

Could someone please "enlighten" me and "correct" my homework? I would like to know what each cap is doing in the circuit and choose accordingly this time. I have tried to gather ALL THE INFO I could find from previous posts and recap projects, including those of the AU-5900 and AU-7700 since they share a lot of the topology.

I follow this rule to simplify my life:
All small caps 0.47ufs, 1ufs and 2.2 ufs etc. -- I replace with WIMAs.
If not signal path: UPW (UPM)
If signal path: UKL preferred. If not (UKA, UFG)
Bi-polars with Nichicon Muse (green ones)

By the way, the board I have is the F-2097 and not the B version. Don´t know if that´s relevant.


C01,C02 - 2.2uf 50V (orange caps) --Very important since they are the "Entrance" of signal into board - Change to WIMAs film or UKLs (low noise)
C13,14 - 1uf 50V (blue caps) -- Part of negative feedback? -- Change to WIMA film or UKL
C05,06 - 100uf 50V (black caps) --Local Decoupling caps. Can be increased? -- Change to UPWs (low leakage)
C11,12 - 100uf 50V (black caps) --Local Decoupling caps. Can be increased? -- Change to UPWs
According to the wonderful help of the master @Leestereo a "decoupling" cap is:

A "decoupling capacitor" can be defined as a power supply capacitor that is located on the close to the circuit to provide local filtering and counteract the inductance from the wiring/traces between the circuit and the main power supply.

C07,C08 - 47uf 50V (black caps) - Bootstrap Caps -- Change to UPW´s - According to the master again,

The bootstrap capacitors at C07/C08 can be ≥100uF.

Used UPW 100uf 63V in my previous recap with no problems.
C09,C10 - 47uf 50V (gray caps) --Negative Feedback? Can be increased? Saw values of 100uf in AU-5900 --Change to UPW 47uf 63V
C25 - 100uf 10V BP (black cap) --Local filtering? Change to a Bipolar Cap, i.e. UES 100uf 16V/25V
C23 - 470uf 6.3V (gray cap) -- protection relay delay circuit (thanks @GlasgowGrip - Change to a UPW 470uf 16V/25V
C27 - 33uf 50V (gray cap) --Local Filtering? Change to UPW 33uf 63V
TR01,TR02 - 2SA726 Differential pair for Left Channel - Responsible for keeping DC Offset at 0 --Change to KSA992 (hfe matched)
TR03,TR04 - 2SA726 Differential pair for Right Channel - Responsible for keeping DC Offset at 0 --Change to KSA992 (hfe matched)
TR29 2SC1364 - Relay Driver Transistor - Can be changed to KSC260 or KSC945C
TR05, 06 2SC1124 - "Uniwatt" Style and can get "tired" - Can be changed to 2SC4793 - thanks @Hyperion

I didn´t see anything on "problematic" diodes or resistors that should be looked at. Of course, the "trimpots" can be changed to "Bourns". Anything else to look for?

Cheers!!!!

 

[CrSens]

I question the need to change all electrolytic caps smaller then 4.7 uF with WIMA film types, it does change the sound, but not necessarily for the better. Do you want to keep the original sound signature, or you want the vintage amp to sound like a semi-modern one?

 

[Zeus12]

Greetings again!

What about the Tone Board (F-2414)? I know the orange caps are "low leakage" types which can be replaced with film (WIMA) or UKL series. What about the rest of the caps? Should they also be low leakage? or better to use low ESR (UPW) series?


For C05,C06 33pf 50V I know @Leestereo would say to use a C0G here. Is this for the high frequency phase shift within the audible range? Keep it at 33pf or change it? I have a 47pf on hand.


I will use WIMAs for all the orange caps, even that 10ufs ones. The 6 problematic trannies will be changed to KSC1845s.

Cheers!!!

 

[Hyperion]

Keep it at 33pf or change it? I have a 47pf on hand.

For what seems like the bazillionth time, replace with the same value that is in your unit NOW, don't change values to the schematic values, it has worked fine and left the factory like that.

N.B.
I notice you have realised that 6.3V electrolytics are not very good.

 

[Zeus12]

Hi @Hyperion

Yes, you are absolutely right. I will keep values AS THEY ARE! Got excited and thought I was "Leestereo" Jr.

So those 6.3V caps are "non-signal" path and can be replaced with low E.S.R. caps?
Caps C03,04,07,08 (47uf 6.3V) and C15,C16 (100uf 6.3V).

Would love to know what they are doing in the circuit Are they "decoupling"/local filtering caps? They are on the "bottom" part of the circuit. Is that part of the "negative feedback" loop?

Cheers!!!

 

[Hyperion]

Would love to know what they are doing in the circuit Are they "decoupling"/local filtering caps? They are on the "bottom" part of the circuit. Is that part of the "negative feedback" loop?

If you refer to LeeStereo's restores he describes the function of most capacitors when noting their replacement component.

 

[Zeus12]

Hi @Hyperion

That´s exactly what I´m trying to do here and OBVIOUSLY you can see that I am a rookie and total newbie at this wonderful hobby. But, I think I have demonstrated, that I WANT TO LEARN.

Thanks for you help.

Cheers!!!

 

[Hyperion]

I understand that, but this subject is best learned from a book, or maybe from someone with many hours to spare explaining things. If you have to take the trouble to read it - you will never forget the information gained.

 

[Zeus12]

Hi again,

I am literally doing the recap of the tone board now. From what I UNDERSTAND, with my limited knowledge, caps C03,04,07,08 (47uf 6.3V) and C15,C16 (100uf 6.3V) are NOT PART of the signal path and do "other" things. So back to my original question, can I use UPWs (low ESR)--keeping the same capacitance and a "bump" in voltage?

If you could CONFIRM that for me, I would REALLY APPRECIATE IT!

Cheers!!

 

[raycarr00]

I'd do it. UPW appear to be great caps!
"Nichicon UPW AEC-Q200 Aluminum Electrolytic Capacitors are miniature sized, low impedance, high reliability capacitors for switching power supplies. UPW series capacitors have a smaller case size and lower impedance than the UPM series. The PW series is also RoHS compliant and highly reliable with a lifetime rating of up to 8000 hours. Nichicon UPW series includes models with voltage ranges of 6.3 to 450V, capacitance ranges of 0.047µF to 15,000µF, and capacitance tolerances of ±20% at 120Hz, +20°C"
check them resistors and look closely at the 2- inductors for burn marks; just replaced one and the resistor next to it which was a metal wirewound covered in black plastic.
you can do it, you can do it! .

 

[Hyperion]

What is, or is not, in the signal path is a very controversial subject, mostly because people's interpretations of how to define it vary. Some people say everything is in the signal path, others have their own interpretations.

In your marked up schematic, you have correctly marked (green) what many regard as the non-signal path capacitors.

 

[Zeus12]

Hi again,

Thanks @raycarr00 for chipping in!

Thanks, as always, @Hyperion! You "adopted" me for my 1st ever recap attempt with a Sansui 661 back in May of 2021. https://audiokarma.org/forums/index.php?threads/sansui-661-hum-problem.938239/page-4#post-14629937

You kind of confused me though. What do you mean by "Some people say everything is in the signal path, others have their own interpretations."? Why would they even sell different caps then? And why would "Leestereo" do those wonderful write ups--which I have printed and keep reading over and over--defining "signal" vs. "non-signal"? Anyways. Should have studied Electronics instead of Economics!!

OK then! Case CLOSED! Will use UPWs (low ESRs) for those caps! Was going to use UFGs for all of them.

Cheers!!!

 

[GlasgowGrip]

Zeus - I definitely agree with @Hyperion's statement "What is, or is not, in the signal path is a very controversial subject, mostly because people's interpretations of how to define it vary." That being said, I would consider C03-04 to be more "signal" than not (feedback loop) and therefore went with a Nichicon UKA (Audio grade) in that position, even though I am splitting hairs. For C07-08 I used a 47uF/25V low ESR (Panasonic FM-series) and for C15-16 I used a 120uF/50V low ESR (Panasonic FM-series) since they are decoupling caps (non-signal). Cheers - Steve

 

[Zeus12]

Hi @GlasgowGrip

Big thanks buddy!!! Really appreciate your input and for sharing the values you used. You definitely cleared my Hi-Fi "doubts" a bit about this tone Board. Still trying to "see" where the feedback loop is and those famous "decoupling" caps. They are in every circuit, from what I have seen.

Maybe I´m just "overanalyzing" this? I would love to be able to speak Hi-Fi "Schematics" like you guys can. All I know is that, less than a couple of years ago, I didn´t even know what a resistor or transistor looked like. At least now I have a vague idea of what the components do.

Will post the fully recapped board!!

Cheers!!

 

[GlasgowGrip]

Hey Zeus - It sounds like you are applying everything you are learning and asking great questions - keep it up and you'll be teaching classes in this stuff before too long!
As for the electrolytic caps, it is extremely easy to get lost in the weeds for usually minimal or even negligible audible difference. Definitely worth paying attention to, but you are on the right path and I would say don't get hung up thinking that there was some "clearly better choice". If you were losing sleep over splitting hairs between picking a UKA instead of a UFG or even a UPW... as far as I know, any of those are going to perform better than the original electrolytics performed when they were new back in 1977 (assuming of course you are paying attention to the basics - capacity and voltage ratings, polar/non-polar, etc.)
Anyway, carry on, you're doing great. Cheers! - Steve

 

[Zeus12]

@GlasgowGrip

I can´t thank you enough for your nice and encouraging words!!! I see you use "positive reinforcement" in your teaching method! Me too!!! I don´t know if I´ll be "teaching" classes in this stuff but I DO KNOW that WHEN THERE IS A WILL THERE IS A WAY!!!

You say, don't get hung up thinking that there was some "clearly better choice". If you were losing sleep over splitting hairs between picking a UKA instead of a UFG. Are you kidding me? I HAVE FULL BLOWN NIGHTMARES!!! I wake up in the middle of the night, thinking about those red WIMAs Every time I desolder a cap, I start to sweat and my "cortisol" levels go up thinking that I might "lift" a trace. What cap should I use? Should I bump it up in value? What does it do exactly in the circuit? I have so many questions. Electricity is so FASCINATING!! The "learning" part now has become just as interesting as the "sound" part.

By the way, do you find the AU-5500 special? For me, to my ears at least, is almost "nirvana" like. It has something about it that just makes it "pleasing". Is it true that Sansui, "colors" the sound a bit, and especially in this series? Does it add 2nd harmonics on purpose? You see what I mean. The more I learn, the more questions I have.

Cheers!!!

 

[Zeus12]

Greetings again!

Tone board came out GREAT!! One happy camper!!!

I used those nice WIMA for ALL the original low leakage caps and UKL for the rest. I was going to use UFG but when I measured and compared a 47uf cap the UKL had a much lower ESR and Vloss.

Original 47uf 6.3V cap:


Nichicon UFG 47uf 16V Measurement:


UKL 47uf 50V Cap Measurement:


Funny how the original cap had a LOWER ESR than the UFG . Decided to use UKL for the rest then. Hope I made the right decision.

Here´s the Tone Board complete:


The Underside. I am very happy I didn´t lift any traces!!! What do you guys think about my soldering?


Big thanks @GlasgowGrip and @Hyperion . I couldn't have done it without this wonderful forum.

Cheers!!!

 

[Zeus12]

Greetings again!

I´m SO HAPPY to see all these likes! Thanks fellows!!! Really appreciate it!!

Here´s the F-2097(B) board fully recapped. Changed all the caps and the 2SA726 differential pair transistors (TR01-TR04) with KSA992´s hFE matched pairs. Also changed the DC offset trimpots (VR01,VR02) and I was able to get the DC offset within 0-10mV for both channels. I also have the VR03,VR04 trimpots on hand but didn´t change them since bias is ROCK SOLID with absolutely no fluctuation. I noticed that it runs cooler than before. Don´t know if the differential pairs were responsible.

F-2097B Driver and PSU Board:


Here´s the F-2091 board fully recapped. I also changed the TR01 2SC1364 with a KSC2690 since that one "died" on me in my previous one.


Took a couple of days for those WIMA caps in the tone board to "settle down" and now it sounds AMAZING!! Typical Sansui--warm, non-fatiguing sound with that beautiful "sparkle".

"Never heard a Sansui I didn´t like".

Cheers!!