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Leestereo's Restoration/Upgrade of a Sansui AU-555A

I don't pop in here much, but I stumbled on this thread while doing some searching. Great work, and as mentioned amazing documentation.
I've got a 555a in my theater system that I use as a phono preamp. I'd love to do an overhaul on it someday.
 
A big thank you to Leestereo for taking the time to investigate and share mods on these beautiful Sansuis.
Your "latest" modification on the 555A (Baxandall Diode and a Vbe Multiplier by-pass capacitor) has totally transformed the amplifier!
The hights are now amazing, there is so much more detail and air that it is scary!
The low end is also so much better, more clearer and solid.

Thank you!!
 
Finally about to start doing these mods on the phono board. Im halfway thru doing the caps.

BUT - had some crackling on the phono stage so I will replace all four trannies that are in there. The SM specifies 2SC871 however interestingly I have 2SC1313 in there.

There are some threads floating around stating that the gain on KSC1845 may not be high enough to replace the 2SC871 in circuit. However I know that he KSC1845 is a pretty good sub for the 2SC1313.

Interesting - so I will swap the 1313's for the 1845's and see how I go, WRT having adequate gain.

Anyone have any views on the gain issue here?

Cheers!
 
Leestereo said:
The last 555A that was on the bench had 2SC1312 transistors (essentially a lower voltage 2SC1313) on the phono and tone boards; these were replaced with KSC1845 (hFE values were ~400). Pictures of this particular unit can be seen here: Repair and Upgrade of a Previously Recapped Sansui AU-555A
Click to expand...
Cheers Lee - and the gain was enough?

Sorry - I looked again and they are indeed 1312's in my phono board.

Kevzep:

Theres some discussion here that 1845's may not be a hi-enough gain to replace the 2sc871 - which are the trannies cited to be in this board in the SM: http://audiokarma.org/forums/index.php?threads/555a-transistor-question-2sc871-r-e-f.757533/

Posters there cite the 2240 as being a possibly better replacement as its higher gain. I dont have any of these but a ton of 1845's.

I will try some higher-gain 1845's.
 
Last edited:
Sweet - done.

I found some 1845's that were around 440hfe. The 1312's that I pulled from the board were not too far off - between 512-540 hfe.

Cheers Lee
 
Dear Leestereo and all others,

Introducing myself: Rudolph from the Netherlands.
Whilst getting excited reading your post about your 555A restoration and upgrade, I decided to do one myself, following your clear and detailled instructions.

I already found out I made at least 3 capital mistakes:

1. As being FULLY new in ALL of this (from electronics to soldering to reading diagrams) , I should have started with a less complex and smaller project. Especially not with an AU-555A!
2. It took me nights and nights of research what to order....there is so much to choose from and it is all abracadabra to me.
3. I should have done the restoration part by part (as mentioned in the end of your explanation).

And of course, it did not went well..... Managed to order parts, to solder them to the circuit boards and to put all back together again, but......... only a very weak "noise" coming out of the speakers (only to be heard when putting your ear close to the speaker, regardless the volume.), and nothing else.

Since I would never forgive myself if I have ruined a 555A, I am begging you for your help if possible, to discover what I did do wrong. I made a part list of what I bought and replaced, and I made a lot of pictures.

Anybody interested helping me? Do you want me to post the pictures and part-lists?

As a reward for helping I promise to send you the best Dutch Gouda Cheese you have ever tasted.

Thank you very much in advance.....

Rudolph
 
Dear Leestereo,

Wow, you are fast!

here is my parts list:
PART 1. POWER SUPPLY
C001 Aluminium Electrolytic Capacitors - Snap In 6800uF 80 Volt United Chemi-Con (UCC) 661-ESMH800N682MA40S
C002 - C004 Aluminium Electrolytic Capacitors - Snap In 1200uF 50V (D X L) 22mm x 25mm Cornell Dubilier 539-LP122M050A1P3
C003 Aluminium Electrolytic Capacitors - Snap In 50V2200uF SNAP Cornell Dubilier 539-LP50V2200
R001 Metal Film Resistors - Through Hole 2watts 1.2Kohms 1% Vishay 71-CPF2-F-1.2K-E3
R002-R003 Metal Film Resistors - Through Hole 2watts 1Kohms 1% 100ppm Vishay 71-CPF21K0000FKE14
D001-D002 Rectifiers Standard 200V 2A Micro Commercial Components (MCC) 833-RL203-TP

PART 2. Tone Control Block F-1272-1
C701-C702 Film Capacitors .47uF 100V 10% Cornell Dubilier 598-474MSR100K
C707-C708 Aluminium Electrolytic Capacitors - Radial Leaded 25volts 10uF 85c 5x11 2LS Nichicon 647-UES1E100MDM
C723-C724 Aluminium Electrolytic Capacitors - Radial Leaded 25volts 10uF 85c 5x11 2LS Nichicon 647-UES1E100MDM
C725-C726 Film Capacitors 0.33 uF 100V 10% Cornell Dubilier 598-334MMR100K
C717-C718 Film Capacitors 1uF 50 Volts 10% WIMA 505-MKS02-1/50/10
C705-C706 Aluminium Electrolytic Capacitors - Radial Leaded 6.3volts 100uF 85c 5x9 2LS Nichicon 647-URS0J101MDD
C721-C722 Aluminium Electrolytic Capacitors - Radial Leaded 10V 47uF -55 to 105C Nichicon 647-UKA1A470MDD1TD
solder side (DC filtering) Aluminium Electrolytic Capacitors - Radial Leaded 35VDC 33uF 5x11mm LS 5.0mm Panasonic 667-EEU-FR1V330B
TR701-TR704 Bipolar Transistors - BJT NPN Epitaxial Sil ON Semiconductor 512-KSC1845FTA
C709-C710 Film Capacitors 50volts 0.033uF 10% LS 5mm KEMET 80-MMK5333K50J01L4
C715-C716 Film Capacitors 50volts 0.033uF 10% LS 5mm KEMET 80-MMK5333K50J01L4
C713-C714 Film Capacitors 0.008uF 100Volts Cornell Dubilier 598-185822J100RAB-F
C711-C712 Multilayer Ceramic Capacitors MLCC - Leaded KEMET 80-C323C202KAG5TA

Part 3. Main Amplifier Block F1266-1
C801-C802 Multilayer Ceramic Capacitors MLCC - Leaded 50volts 10pF KEMET 80-C410C100K5G
C803-C804 Film Capacitors 1uF 250VDC 5% MPP L/S=15mm Panasonic 667-ECW-F2105JA
C807-C808 Aluminium Electrolytic Capacitors - Radial Leaded 16volts 470uF 85c 12.5x25 5LS Nichicon 647-UES1C471MHM
C819-C820 Aluminium Electrolytic Capacitors - Snap In 6800uF 42 Volts 20% Tol. Nichicon 647-LKSA2682MESB
C809-C810 Aluminium Electrolytic Capacitors - Radial Leaded 25volts 47uF 20% Nichicon 647-UFW1E470MDD
R811-R812 Metal Film Resistors - Through Hole 150ohm 1% 50PPM KOA Speer 660-MF1/4CCT52R1500F
R813-R814 Metal Film Resistors - Through Hole 4.7K 1% 50PPM KOA Speer 660-MF1/4CCT52R4701F
R815-R816 Metal Film Resistors - Through Hole 1/4 WATT 5.6K OHM 1% KOA Speer 660-MF1/4DCT52R5601F
TR801-TR802 Bipolar Transistors - BJT PNP Epitaxial Sil ON Semiconductor 512-KSA992FBU
C813-C814 Aluminium Electrolytic Capacitors - Radial Leaded 50VDC 120uF 8x15mm LS 5.0mm Panasonic 667-EEU-FR1H121LB
C815-C816 Aluminium Electrolytic Capacitors - Radial Leaded 6.3volts 470uF 85c 10x12.5 5LS Nichicon 647-UFG0J471MPM
C821-C823 Film Capacitors .47uF 5% 100volts Vishay 594-2222-367-26474
C822 Aluminium Electrolytic Capacitors - Radial Leaded 100VDC 330uF 2380mA Polar Panasonic 667-EEU-FS2A331L
C805-C806 Film Capacitors 100V 1uF 5% KEMET 80-F612JT105J100R
C824-C825 Aluminium Electrolytic Capacitors - Radial Leaded 80VDC 47uF 490mA Polar Panasonic 667-EEU-FS1K470
VR813-VR814 Trimmer Resistors - Through Hole 1K Ohms 1% Fail Rt 1/4" Cermet Mil-Spec Bourns 542-RJR26FW102M
VR811-VR812 Trimmer Resistors - Through Hole 20Kohms Sealed 6mm SQ 12turn Bourns 81-PV37W203C01B00

Part 4. Power Amplifier Modifications
R835-R836 Metal Film Resistors - Through Hole 1/4 WATT 150 OHM 5% KOA Speer 660-MF1/4LCT52R151J
R835-R836 Rectifiers Vr/100V Io/1A Glass Passivated Vishay 625-1N4002GPE-E3/54
TR805-TR806 Film Capacitors 0.33 uF 100V 10% Cornell Dubilier 598-334MMR100K
R823-R824 Metal Film Resistors - Through Hole 825ohm 1% 100PPM KOA Speer 660-MF1/4DC8250F

Part 5. Equalizer (Phono) Block F-1267
C601-C602 Film Capacitors 630VDC 0.47uF 10% MPP L/S=15mm Panasonic 667-ECW-FD2J474K
R601-R602 Metal Film Resistors - Through Hole 2.2K ohm 1% KOA Speer 660-MFS1/4DCT52R2201
R619-R620 Metal Film Resistors - Through Hole 1/4W 332K Ohms 1% KOA Speer 660-MS1/4DCT52R3323
R623-R624 Metal Film Resistors - Through Hole 27.4K 1% 50PPM KOA Speer 660-MF1/4CC2742F
C613-C614 Multilayer Ceramic Capacitors MLCC - Leaded 50V 0.01uF X7R 10% RAD LS:2.5mm AECQ200 TDK 810-FA18X7R1H103KNU6
C615-C616 Multilayer Ceramic Capacitors MLCC - Leaded RAD 50V 2700pF C0G 5% LS:2.5mm TDK 810-FG18C0G1H272JNT6
C607-C608 Aluminium Electrolytic Capacitors - Radial Leaded 25V 22uF -55 to 105C Nichicon 647-UKA1E220MDD1TD
C609-C610 Aluminium Electrolytic Capacitors - Radial Leaded 6.3V 100uF -55 to 105C Nichicon 647-UKA0J101MDD1TD
C611-C612 Film Capacitors 100V 1uF 5% KEMET 80-F612JT105J100R
F-1267 BOARD Aluminium Electrolytic Capacitors - Radial Leaded 35VDC 33uF 5x11mm LS2mm Panasonic 667-EEU-FR1V330
 
This is what I could not do (or could not find out):

1. VR811-VR814 Trimmers on MAIN AMPLIFIER BLOCK: No idea how to set these up (don't have an Digital Oscilloscope), so left the screws untouched.
2. TR701-TR704 transistors on TONE CONTROL BLOCK: it was almost guessing how to put the leads; E-C-B was not printed on the circuit board (so I hope the old leads are the same as the new ones: new ones I know the leads, old ones I couldn't find a proper data-sheet (the 2SC63A).
3. Could I have damaged something by soldering too long (overheating)?
 
Thanks a million Leestereo! I will get into it first thing tomorrow (it is evening here, and the wife is ordering me in the living room....).
if this would solve the problem..... I will let you know tomorrow! I hope you like cheese!!!
 
Looks like nice work otherwise! Swap those transistors around and let us know how it goes! Curious why you never replaced the driver amp board transistors??
 
If you have an issue like this - you can seperate the amplifier sections for testing - ie: you can run RCA cables out from the "pre out" RCA sockets at the back to another amplifier to test the preamp stage, and also run a music source (set at a very low volume!) straight into the "power amp in" RCA sockets at the back of the amplifier.
 
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