Sansui 5050 - F-2647 Driver Board Restore

[Zeus12]

Greetings fellow audiophiles,

Starting doing a recap and restore of a Sansui 5050. I have finished the PSU board (F-2701), used Nichicon UPWs throughout and now working on the Driver Board (F-2647).

This is what I have done so far:


1. I know I have to change TR01-04, marked with a red X. These are the "input differential gain" pair and need to be closely matched (hfe) which in turn will effect the DC Offset. The better matched, the closer it will be to 0mV. Best replacement is KSA992.
2. The 4 units of "Fusible resistors" of 220ohm 0.25w (R31,R32,R33,R34), marked with a yellow exclamation mark. These are "problematic" and best choice would be to change them with metal/carbon films. Would these be OK? https://www.mouser.es/ProductDetail/KOA-Speer/CF1-2C221J?qs=qdOgYJ2iURWrrVcwhP2nBA==
3. Can I change the 4 remaining caps, marked with a blue question mark, with a Bipolar Nichicon UES? I know that @Leestereo mentioned in a thread that for everything in the signal path, a Bipolar would be better. Would I hear the difference over using an FG cap, for example?
4. What about the little black cap, above the 2 WIMAs? Is that an "audio" path cap. Should I use a UPW (low esr) for that one?

Cheers!!!

 

[Leestereo]

...2. The 4 units of "Fusible resistors" of 220ohm 0.25w (R31,R32,R33,R34), marked with a yellow exclamation mark. These are "problematic" and best choice would be to change them with metal/carbon films. Would these be OK? https://www.mouser.es/ProductDetail/KOA-Speer/CF1-2C221J?qs=qdOgYJ2iURWrrVcwhP2nBA==

The linked resistors are rated at 0.5W, better to use 0.25W metal film types to replace the fusitors.

3. Can I change the 4 remaining caps, marked with a blue question mark, with a Bipolar Nichicon UES? I know that @Leestereo mentioned in a thread that for everything in the signal path, a Bipolar would be better. Would I hear the difference over using an FG cap, for example?

These capacitors are NOT in the signal path; C07/C08 are decoupling capacitors for the B- and C09/C10 are bootstrap capacitors for the Vas. The replacement capacitors can be low ESR types.

4. What about the little black cap, above the 2 WIMAs? Is that an "audio" path cap. Should I use a UPW (low esr) for that one?...

The capacitor C601 shunts the ZD601 zener; replacement can be a low ESR type.

 

[Zeus12]

Big thanks @Leestereo

Always a pleasure to see a response from one of the "gurus"!!! I am dying to "speak" Hi-Fi schematics like you! Got the idea that they were in the "signal" path from here: I wonder why he chose Nichicon UKA´s for those caps? He looks like he knows what he´s doing.
http://marantzhallo-fi.blogspot.com/2017/10/pauls-sansui-5050-receiver.html

1. OK then, I will use Nichicon UPW series for C601 and C607-C610. If I remember correctly, you also mentioned that it´s OK to increase the value for the bootstrap capacitors?? For example, on the Sansui AU-5500, C07,C08 can be increased to 100uf from the original 47uf. Is it necessary for the 5050?

3.

For the driver boards (F-2647), the small ceramics in the signal path, i.e., C03/04 (low-pass filter) and C11/12 (feedback loop) can also be upgraded to C0G types.

Also, for C03/04 on F-2647, you mentioned to reduce the value to 47pF (originally 220pf) to eliminate the phase shift within the audible range. WOW!!! That´s the master speaking!!! Capacitors C11/12 are 3pF and can be kept at the same value.
I would imagine, these changes are for the super audiophiles that have "super" hearing. Am I going to hear it?

Here´s the F-2701 board fully recapped (UPWs):

Cleaned the underside and took "extra" care to do a nice soldering job:


Here´s the Phone board, partially recapped. I increased C601 from 220uf 50V to a UPW 330uf 63V--which I got the idea from you of course. This is a "decoupling" cap and the theory is that it will have more "cleaner" reserve power for the surrounding components? Should I also change those Tantalums caps C01, C02 and C602 (3.3uf 35V)? I would imagine a WIMA would be the best option--if it can fit--and UES if not?

Underside of the Phone board:


Couldn´t have done it without this forum!!!

Cheers!!!

 

[Leestereo]

...1. OK then, I will use Nichicon UPW series for C601 and C607-C610. If I remember correctly, you also mentioned that it´s OK to increase the value for the bootstrap capacitors?? For example, on the Sansui AU-5500, C07,C08 can be increased to 100uf from the original 47uf. Is it necessary for the 5050?

Yes, the bootstrap capacitor can be increased from 47uF to 100uF without worry.

Here´s the F-2701 board fully recapped (UPWs):
View attachment 2623494
Cleaned the underside and took "extra" care to do a nice soldering job:
View attachment 2623495

Very nice work. Note that Sansui installed 0.047uF Vbe-multiplier by-pass capacitors on the solder side of F-2700; these ceramic types can upgraded to a small film type, e.g., 0.1uF or 0.22uF.

Here´s the Phone board, partially recapped...Should I also change those Tantalums caps C01, C02 and C602 (3.3uf 35V)? I would imagine a WIMA would be the best option--if it can fit--and UES if not?
View attachment 2623505
Underside of the Phone board:
View attachment 2623508...

Yes, it is recommended to replace the signal path tantalum capacitors (C01/C02) with bi-polar electrolytic capacitors or film types; the tantalum at C602 can be replaced with a low ESR electrolytic type. Also for more accurate RIAA equalization, the 390kohm resistors at R15/R16 should be replaced with 332kohm ones.

Picture originally posted in this AK thread

 

[Zeus12]

OK @Leestereo

Can´t thank you enough for all your help and guidance! Thanks for the compliment on my soldering!! I REALLY TAKE my time. Better safe than sorry!

OK. Will take note of all the changes you mentioned. I think I have read ALL your restoration threads on here so yes, that´s where I got the idea of increasing the decoupling cap to 330uf for the Phone board. By the way, can I use a WIMA 3.3uf for the tantalum at C602 instead of a PW for example?

Just on last thing, any more tips on removing the Tone Board? I tried but I am afraid of messing up the Tuner string. I saw this link but just in case you had any more tips on how to go about doing it. https://audiokarma.org/forums/index...050-6060-tips-on-accessing-tone-board.941233/

Cheers!!

 

[Leestereo]

...By the way, can I use a WIMA 3.3uf for the tantalum at C602 instead of a PW for example?...

Yes, but its not really necessary to install a film capacitor replacement for C602.

...Just on last thing, any more tips on removing the Tone Board? I tried but I am afraid of messing up the Tuner string. I saw this link but just in case you had any more tips on how to go about doing it. https://audiokarma.org/forums/index...050-6060-tips-on-accessing-tone-board.941233/
...

The information in that thread is correct wrt gaining access to the F-2646 board.

 

[Zeus12]

Greetings again!

Here´s my Sunday morning activity. WOW!!! What a big difference. I have been sonically ENGLIGHTENED again! It is sounding a lot cleaner, crispier and LUSH!

1. To remove the tone board, I literally had to sweat and CAREFULLY pull it out. I managed to do it without cutting any original wire wrappers.


2. Upped C601 cap to a 330uf 63V UPW, used a UFG 100uf 16V for C19,C20 and WIMAS for the rest of the caps. The 2SC1313 trannies replaced with KSC1845´s. By the way, I matched all 4 by hfe. Don´t know if that was necessary here.


Underside. Very happy I didn´t lift any traces. This is the most stressful part for me.


The difference in sound is NIGHT and DAY. Didn´t know the 5050 could sound so sweet and lush. And it can still sound better since I have some caps, trannies and the metal resistors to put in. I love it how it is sounding so far!!

Again, big thanks to @Leestereo for guiding and helping me along the way!! When I "grow up", I want to be like you!!