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.