My never ending expansion of audio equipment brought home small Sansui AU-101 amplifier. This is a 2x15W stereo amplifier built between 1973 and 1975. Contrary to all the other silver faced audio equipment of that era, this one is all black with wood panels on the sides. As an entry level amplifier, it only supports one pair of speakers but has features like microphone in and front panel jack for tape monitor.
The condition of the amplifier was pretty good for almost 40 years old piece of vintage audio equipment. I used to have Sansui 771 receiver that I gave to my parents. Since then I have always missed the warm and bass heavy sound of Sansui. Well, after about a year, I finally had my chance to enjoy this sound again.
I did a quick sound test by listening to my favorite tracks and decided to do a full recap. Not because there was anything wrong but as a preventive maintenance. Also, after recapping my Marantz receiver last summer I knew that the sound can only improve when all the old capacitors are replaced with new ones. My Marantz got all Nichicon capacitors so this time I wanted to go for something else. Decided to go with Panasonic FM/FC type because many people were praising those. Cost wasn’t really a deciding factor here because this small amp has only 31 capacitors so even if the price was double what the Panasonic FC costs, I still wouldn’t have to break my piggy bank. Total cost for all caps was $15.36 plus shipping from Mouser.com. The cap list can be found here: Sansui AU-101 capacitor list. Please note that I was changing only electrolytic capacitors. There were also no tantalums so the list contains only ECs. There were few substitutes that I have made. The big smoothing capacitor’s value was upgraded from 1,000uF to 2,200uF (same voltage) and few other caps got voltage upgrade. I have picked FM type or FC wherever the FM wasn’t available (actually Mouser had only handful FM caps that I needed).
New capacitors arrived in about three days and I was ready to begin my work. With the top cover and bottom panel removed I have started with the tone board. With this one I had to remove all nuts from all the pots and then I was able to swing it back and up. The first cap revealed a small problem. The leads of existing caps were bent parallel to the PCB so using desoldering iron, removed all the old solder but left the leads attached to the PCB. When I tried to lift the lead with small screwdriver I have pulled it with the trace. No good! Well, this one I was able to save by repairing the trace with solder and used the digital multi-meter (DMM) to make sure the connection was made. After that, I have decided that the best way to remove those caps is to remove the excess solder with the tool and then heat up lead and try to wiggle the cap out of the board. That worked fine.
Little over one hour later the pile of old capacitors looked like that:
I have spent another few minutes cleaning potentiometers and switches with Deoxit. Since the cleaner solution gets not only into pots, I have decided to leave the unit open overnight to let it dry out.
Next day with my safety glasses on and the amp connected to a bulb tester, I have switched the power on. There was no fire or exploding caps. Next I have tried to connect my iPod, switch the speakers on (without actually having speakers connected to the amp) and turned the volume up. Still no smoke. Next, I have plugged my headphones and heard the sound. Success!
I have used the same source, same headphones and the same tracks that I have tested on the amplifier before recap. The change in sound was noticeable and it was a good change. I am not good at describing how sound sounds but the notes were clear and the songs were more dynamic. There was plenty of low notes even without the loudness switch on and with all the tone controls zeroed out. I have heard that the sound will be even better after “burn-in” process but I doubt that I will be able to tell the difference. I think pre-recap and post-recap difference is the most noticeable one.
At the end here are few shots of the boards:
Amplifier board (before recap):
Amplifier board (after recap):
Tone board (before recap):
Tone board (after recap):
You can see that all the new capacitors are smaller than the old ones. For the most part that doesn’t matter but you may have problems with securing some of the bigger filter caps. It wasn’t the case with this amplifier but I still added some hot glue between the capacitor and PCB for the 5 biggest caps.
I am going to use this amplifier mainly for a headphone use but I still want to replace the screw based speakers terminals with real binding posts. That should be easy though.
Now back to enjoying the sweet Sansui sound.
25 thoughts on “Sansui AU-101 amplifier recap”
Nice work.I like to recap also a sansui AU-101,but came to a question about the 1000µf 50 volt cap.Is this a special cap because it’s got 3 leads?
If I remember correctly, two of those three leads were soldered together so check the trace on the PCB. Also the side of the cap has description of all three leads.
I got the same one a few days ago. Sounds real good. almost perfect. but I found that there is some noise at one channel. I don’t know what I should call it. Left channel has the noise of (shuuuu..high tone.) specially at the tweeter. It gets bigger when I turn the volume up. I think I can use it without fixing it, as it is good enough. But better is better.
If you have some solution, let me know
Big thanks for posting up the cap list – I just made an order based on your spreadsheet. How are you going with this amp? Did you make any more mods after writing this post?
David: You may want to post for help at AudioKarma.org forum. If you have the older version with flying saucer transistors, I would suspect them. If not, you would have to do some basic troubleshooting to figure out what the problem is.
innerwestsoul: I no longer have the AU-101. I have sold it when I picked up the Sansui 661 receiver. You can look at this post http://audio44.wordpress.com/2012/04/06/upgrading-speaker-binding-posts-in-sansui-au-101/ for the speaker binding mod.
once you have fully recapped it how do you perform a bias check/set?
Jon, take a look at this post on AudioKarma. It explains the procedure of checking bias: http://www.audiokarma.org/forums/showthread.php?t=435511
The last picture gives me better understanding. So you connect to the Far right resistor and the Far left resistor and allow certain temp and ensure that Multimeter is set to DC mw and check bias if it is above or under 10mv then you need adjust it. I understand that in standby mode the volume should be 0 and tone control should be left in center. But does it require a load (connecting to speakers)?
BTW, stuck with the 3 leg capacitor any help would be much appreciated.
I don’t think my model has bios adjustments. Is this self adjusting?
You do not need a load on the speakers. You can adjust bias if you have the VR80x trim pots. If you do not, you can’t. I think older models with “flying saucer” transistors did not have the trim pots. As to the 3 leg capacitor, only two leads are actually used. The third is not used so you can replace this capacitor with new one that only has two leads (negative and positive). Hope this helps.
Powered it on and luckily no smoke. Then connected CD player and speakers and selected AUX to play cd’s. Turn the volume slowly up and there was sound much more powerful than before – nice and smooth and will get better. I used FC.FM for main caps. The rest were mixture of EB,FR, FC, GE – I customed this my self. So far happy with the sound. I was thinking about NIchicon (Audio grade standard- £67) but I think there would be very little difference and did not take the risk. Very happy indeed. Week ago did not even no what a capacitor was and week later successfully manage to recap entire amp with your help, Thanks Alex your right up was great help. NIce one.
After just 2 hours of continuous play its getting more smoother and has even greater dynamics – more resolution. Bass has gone very tight (not boomy) too;very impressed. Should have tried Nichicon Audiophile grade capacitors- this will remain a mystery.
Just to rectify that I powered the amp down before connecting speaker and cd player.
Good job Jon! I am glad you were able to finish the recap and can now enjoy your amp. Don’t stress too much about the capacitor brand/type. While I could hear the difference between the old vs new caps, I doubt I would hear such difference if I upgraded to a different caps. BTW, if you think of restoring more equipment, look up dim bulb tester (DBT) if you don’t already have one. It could save you tons of headache in case something goes wrong with the recap.
Next replacing binding post – have ordered it(this should be easy and fun).
Good idea, will also build a dedicated DBT – your right Safeway comes first, cheers for that Alex.
What do you make of these far east ESR/Transistor/Diode/inductor tester? only between £10 -£15 on Bay.
I use a multi-meter to test diodes and transistors. No experience with the gear you mentioned. Sorry.
I have bought a Pioneer A400 with one channel faulty (should receive it in couple of days), what are the common faults? and what should I check for?
Sorry for a late reply. Unfortunately, I am not familiar with the Pioneer you have so I can’t provide assistance.
Great post. I have the same amp and have been missing it since one of the speaker channels went dead and I couldn’t afford to get it repaired. I’d be quite up for fixing it myself that would be pretty rewarding but challenging vas I haven’t any electronic experience! Found the manual online looking into it. ..
salve se potete aiutarmi o acquistato un sansui au 101 e mi piace anche se o scoperto che a un canale con i trastistor non originali , potreste dirmi dove potrei trovarli ?
Mario, service manual is available on HiFiEngine website. It should list the original part numbers which should help you locate replacements. If a quick search on Mouser or Digikey doesn’t provide any hits, I would sign up for a forum called AudioKarma.org and ask question there. Tons of knowledgeable people there that may recommend a suitable replacements.