Tran Vinh Tho
03-05-2006, 12:33 PM
Hi ,
I have just acquired a Sansui intergrated amp. That is AU-X1. I heard a lot on this forum about the oscillation of this amp. Unfortunately, my AU-X1 must have been in the same situation because all the output transistors were replaced. This was done in Japan. Except for this, all other things are in original condition. I have swiched it on and listened to it 3 times up to this moment, abt. 2 hrs each. It sounds alright, both channels seem equally warm. I have not checked the bias or DC offset yet There are some questions I really need you here on this forum to give some light to:
1- The transistor replacements are NEC 2SB600/2SD555 on one channel, and SANSUINMA1718/ NMC1718 on the other channel. Are the specs of these replacements similar to the original SANKEN 2SC2493N/ 2SA1068N ? These replacements are OK or not ?
2- The post by Warren on this forum shows that the mods should be made to the power section and the phono section. The fact that the output transistor replacements should be MOTOROLA MJ21193/MJ21194 does help to prevent the amp oscillation or not? Or they are simply the normal replacements for the blown-out Sanken ones? The mods to the phono part is really necessary for the stabability of the amp? I ask this because I have no intention to use the phono of the amp.
3- A gentleman told me another way which he heard to modify the AU X1 < Replace C29 (680pF) with 1500pF, R07 (470 Ohms) with 100 Ohms on the F-2775 board >
What do you think about this, Warren? So I have to choose one of these two ways or they can be combined?
Looking forward to your opinions.
Rgds,
Tran Vinh Tho
I have just acquired a Sansui intergrated amp. That is AU-X1. I heard a lot on this forum about the oscillation of this amp. Unfortunately, my AU-X1 must have been in the same situation because all the output transistors were replaced. This was done in Japan. Except for this, all other things are in original condition. I have swiched it on and listened to it 3 times up to this moment, abt. 2 hrs each. It sounds alright, both channels seem equally warm. I have not checked the bias or DC offset yet There are some questions I really need you here on this forum to give some light to:
1- The transistor replacements are NEC 2SB600/2SD555 on one channel, and SANSUINMA1718/ NMC1718 on the other channel. Are the specs of these replacements similar to the original SANKEN 2SC2493N/ 2SA1068N ? These replacements are OK or not ?
2- The post by Warren on this forum shows that the mods should be made to the power section and the phono section. The fact that the output transistor replacements should be MOTOROLA MJ21193/MJ21194 does help to prevent the amp oscillation or not? Or they are simply the normal replacements for the blown-out Sanken ones? The mods to the phono part is really necessary for the stabability of the amp? I ask this because I have no intention to use the phono of the amp.
3- A gentleman told me another way which he heard to modify the AU X1 < Replace C29 (680pF) with 1500pF, R07 (470 Ohms) with 100 Ohms on the F-2775 board >
What do you think about this, Warren? So I have to choose one of these two ways or they can be combined?
Looking forward to your opinions.
Rgds,
Tran Vinh Tho