smurfer77
Super Member
I picked my wife up from the train station today and had to warn her... there is a monster at home. The box is marked "heavy 69lbs". I've had a 110lb amp before, but this will be the heaviest amp I've worked on myself so far. What is the monster? Well from the title you already know it is a Sansui AU-X11. And, although I have several other projects unfinished, I've never worked on any of the 'newer' sansui and can't wait to get stuck in. The amp is meant to be stuck in protection mode. So here we go on another adventure. Am very excited to be working on something completely new to me. (In fact, I've never worked on a Sanui modern enough to have a relay!)
The unit took a hit in shipping, but nothing too bad... the usual minor damage to wood side panel corners. After taking over several panels and covers I get to see the beasts guts. Very impressive inside. 80,000 uF of caps sitting right in the middle. Very beefy looking overall. What is immediately obvious is that the chassis ins't that beefy. It's actually pretty flimsy compared to what I'm used seeing inside of the older amps. Surprising for a unit carrying such heavy iron etc. You can flex the chassis with one finger! Additionally, the material rusts easily. My unit has the typical surface rust you see on almost all images of AU-X11. There is even some rust on the main transformer. Anyway, I will get to all of that later. I also see a fair amount of flimsy cabling and poor design in terms of mechanical and electrical reliability. I will do some rewiring and get rid of some of the crappy ribbon cables used (you know the type that you touch and it breaks the wire at PCB end because the cable housing is slightly inflexible and it stresses at the point where the exposed wire meets the housing). Oh, and I see some of the nasty glue used on caps eating away at resistor legs, especially on the board (presumably tone/preamp) behind the front panel - some of those resistor legs have turned into a frothing green mess. So after repair of the main issues and getting sound going nicely, I think a restoration of all boards is probably in order.
The machine was meant to be in protection mode. But I look around a bit before trying to bring it up... and I can't find anything nasty looking. So I fire it up, wearing safety googles, half expecting something to explode in my face as I'm leaning over to keep an eye on things, going between checking meters and watching for magic smoke related issues. As I turn up to about 40 V, CLICK, a relay triggers and I'm out of protection mode (NICE!), then at 70-80V a few more clicks as the other relays tick over. So far, so good.
I turn on a source and use my workshop speakers (a couple of woofers from some parted KLH 17 speakers sit permanently on my workbench... no need to risk any speakers I care about). Right channel is weak but has sound, left channel has nothing. I twiddle the volume knob a bit and the right channel come on strong, and I start to think about what output relays the machine has that might need cleaning. However, I attempt to bias up and right channel is fine, and left channel is stone cold. Nothing. So the intermittent right channel is something to do with the volume pot. Confirmed by further fiddling (I can make the channel weak/strong by pushing the volume knob without changing the volume setting... so I can forget about the output relays for now).
I know nothing about the AU-X11 until today. So let's see what happens. If anyone has schematic or manual, let me know. I assume the manual would be in Japanese... I may be able to translate it if someone gets hold of it.
Okay, so summary is: (1) fix volume pot intermittent right channel issue. (2) Left channel dead: check power supply to left driver/outputs, and if that's good pull the board and see what's what. On that note, Stereofun (and others) did you end up finding a supply for the high speed outputs (I remember you had a thread on something about that a while back)???
And, those of you who know me will not be surprised..... many pics to come.
The unit took a hit in shipping, but nothing too bad... the usual minor damage to wood side panel corners. After taking over several panels and covers I get to see the beasts guts. Very impressive inside. 80,000 uF of caps sitting right in the middle. Very beefy looking overall. What is immediately obvious is that the chassis ins't that beefy. It's actually pretty flimsy compared to what I'm used seeing inside of the older amps. Surprising for a unit carrying such heavy iron etc. You can flex the chassis with one finger! Additionally, the material rusts easily. My unit has the typical surface rust you see on almost all images of AU-X11. There is even some rust on the main transformer. Anyway, I will get to all of that later. I also see a fair amount of flimsy cabling and poor design in terms of mechanical and electrical reliability. I will do some rewiring and get rid of some of the crappy ribbon cables used (you know the type that you touch and it breaks the wire at PCB end because the cable housing is slightly inflexible and it stresses at the point where the exposed wire meets the housing). Oh, and I see some of the nasty glue used on caps eating away at resistor legs, especially on the board (presumably tone/preamp) behind the front panel - some of those resistor legs have turned into a frothing green mess. So after repair of the main issues and getting sound going nicely, I think a restoration of all boards is probably in order.
The machine was meant to be in protection mode. But I look around a bit before trying to bring it up... and I can't find anything nasty looking. So I fire it up, wearing safety googles, half expecting something to explode in my face as I'm leaning over to keep an eye on things, going between checking meters and watching for magic smoke related issues. As I turn up to about 40 V, CLICK, a relay triggers and I'm out of protection mode (NICE!), then at 70-80V a few more clicks as the other relays tick over. So far, so good.
I turn on a source and use my workshop speakers (a couple of woofers from some parted KLH 17 speakers sit permanently on my workbench... no need to risk any speakers I care about). Right channel is weak but has sound, left channel has nothing. I twiddle the volume knob a bit and the right channel come on strong, and I start to think about what output relays the machine has that might need cleaning. However, I attempt to bias up and right channel is fine, and left channel is stone cold. Nothing. So the intermittent right channel is something to do with the volume pot. Confirmed by further fiddling (I can make the channel weak/strong by pushing the volume knob without changing the volume setting... so I can forget about the output relays for now).
I know nothing about the AU-X11 until today. So let's see what happens. If anyone has schematic or manual, let me know. I assume the manual would be in Japanese... I may be able to translate it if someone gets hold of it.
Okay, so summary is: (1) fix volume pot intermittent right channel issue. (2) Left channel dead: check power supply to left driver/outputs, and if that's good pull the board and see what's what. On that note, Stereofun (and others) did you end up finding a supply for the high speed outputs (I remember you had a thread on something about that a while back)???
And, those of you who know me will not be surprised..... many pics to come.
Last edited: