Repair and Upgrade of a Previously Recapped Sansui AU-555A

Leestereo

Super Member
On the bench is a Sanusi AU-555A that was sent in by an AK member for repair and upgrade. The background on this unit: the owner had this unit recapped (approximately a year ago by a tech local to him), but was less than satisfied with the results. Aside from the lackluster sound following the recap, the owner noticed that there was now a loud turn-on "pop", whereas there were none before. Also problematic was the intrusive background noise with the phono input, and affecting all inputs was the sound dropping out in the right channel. The unit was brought back to the original tech on two occasions, but the issues remained and hence the owner contacted me: "I'm interested in the full restoration, l already have a recap and it's not satisfactory. I can't use it or sell it so let's get it to spec."

Here are pictures of the recapped unit as received.

index.php


index.php


index.php


index.php


index.php


index.php


index.php
 
The cause of loud turn-on "pop" was a broken trace (indicated by a yellow circle in picture below) on the Main Amplifier F-1266-1 board at a capacitor (C822). This capacitor is part of the regulated supply circuit which feeds the input transistors for the main amplifier. The intermittent sound in the right channel was due to oxidized contacts in the tape monitor switch. Having addressed the functional issues, the next step is upgrading the unit as per this previous thread: Leestereo's Restoration/Upgrade of a Sansui AU-555A.

index.php
 
Last edited:
Lovely, really excellent.

Perhaps a forgone conclusion, :thumbsup: but it'll be nice to hear a follow up from the owner regarding how it sounds now after this beautiful re-work. ;)
 
...it'll be nice to hear a follow up from the owner regarding how it sounds now...

IIRC, the owner of this particular 555A doesn't post much, but he did send me this message afterwards: "Wow, l'm very impressed. Tons of power, excellent from top to bottom with a silky clarity. And an awesome phono stage as promised."
 
Nice work,are those Mylar caps ? I see In the photos ,so how much difference do they make in sound quality. Ken
 
Ken: The signal path electrolytic capacitors were replaced with mylar (polyester) WIMA-brand stacked film types and the stock green mylar capacitors were upgraded to polypropylene film types or C0G types. IMO, the film capacitor upgrades do noticeably improve the sound, but equally important are the Baxandall Diode and the Vbe Multiplier capacitor mods (click here for more detail on these).
 
On the bench is a Sanusi AU-555A that was sent in by an AK member for repair and upgrade. "

There are too many positive reviews regarding the Baxandall Diode.
I am curious. Would be the Baxandall Diode and a Vbe Multiplier by-pass capacitor mod work for a small brother Sansui AU-222?
 
Back
Top Bottom