Sansui AU-X11 repair and restoration
- Thread starter smurfer77
- Start date
http://audiokarma.org/forums/index....-x11-restoration.788908/page-12#post-12329367
NB: @Serggsa Please don't place identical questions in two threads.
Last edited:
The Fuxtor
Addicted Member
Picking this one up again...
Just finished fixing one of these, and just want to double check the bias settings? My unit uses 0.22ohm emitter resistors, should my bias be set to 11 mv or 22mv?? I set it to 11 mv and the heatsinks hardly even warm up? Seems to me they should be at least warm after playing it for over an hour? Kinda hard to believe that no service manual has emerged as of yet...
Just finished fixing one of these, and just want to double check the bias settings? My unit uses 0.22ohm emitter resistors, should my bias be set to 11 mv or 22mv?? I set it to 11 mv and the heatsinks hardly even warm up? Seems to me they should be at least warm after playing it for over an hour? Kinda hard to believe that no service manual has emerged as of yet...
It should be 12mV across two 0.22Ω emitter resistors according to the information I have.
This gives a bias current of 27mA per output transistor pair.
V/R = I
0.012V/0.44Ω = 0.027A = 27mA
This bias current should be enough to take the 'chill' out of cold heatsinks after about 30 minutes.
(note this will be a total of ~100mA for the 4 pairs of OP transistors).
You should double check that you are adjusting it correctly, between the right points, and that your meter isn't faulty.
NB: There is a partial service manual the 'crowd sourced' one, which has just the basics.
This gives a bias current of 27mA per output transistor pair.
V/R = I
0.012V/0.44Ω = 0.027A = 27mA
This bias current should be enough to take the 'chill' out of cold heatsinks after about 30 minutes.
(note this will be a total of ~100mA for the 4 pairs of OP transistors).
You should double check that you are adjusting it correctly, between the right points, and that your meter isn't faulty.
NB: There is a partial service manual the 'crowd sourced' one, which has just the basics.
Last edited:
The Fuxtor
Addicted Member
I'm adjusting it properly... I'm guessing it's due to the garage environment? It's a touch cooler in there.
I've been pleasently surprised how well this unit has dialed in all of the adjustments. Really nice sounding model !!
The Fuxtor
Addicted Member
Another kick at the cat..... I got this unit back because it keeps blowing the right channel ( repaired channel) . I used Hyperions guide on T03p conversion from his BA-F1 restore post. All was good last time for over 36 hours straight at my place ( with 4 speakers for 4 ohm load).
After he received it back the channel blew again not long after. After about of digging I discovered his step down transformer was a 110/100 volt unit. He was actually giving it 115v ! our wall voltage is typically 120-122acv
. Thinking that may be the problem . I get it back and repair the blown outputs , check the emitters and drivers ( all good). Buttoned it up today and played it on phono this time as the owner uses only the phono... It blows after maybe 20 minutes????
After each repair the adjustments all dial in perfectly and stable?? Possible that the phono stage is responsible??
After he received it back the channel blew again not long after. After about of digging I discovered his step down transformer was a 110/100 volt unit. He was actually giving it 115v ! our wall voltage is typically 120-122acv
. Thinking that may be the problem . I get it back and repair the blown outputs , check the emitters and drivers ( all good). Buttoned it up today and played it on phono this time as the owner uses only the phono... It blows after maybe 20 minutes????
After each repair the adjustments all dial in perfectly and stable?? Possible that the phono stage is responsible??
Last edited:
The Fuxtor
Addicted Member
I have this all up and running again... This time I used some larger Mica pads and actually got the base and emitter legs isolated just in case they were a tad too close to the heatsink? I've got this playing they the phono stage but I'm keeping a close eye on the bias and my killawatt meter looking at the amperage it's pulling. So far all is good again?? I'm thinking I need to be checking for high frequency oscillations... Do I set my signal generator for 15k- 20k?? I believe the higher frequencies are the killers with oscillations??
