Restoring a Sansui AU-X1

[wmac]

Everything is in place, tested under DBT, and working fine; the power relay and output relay are working. Now, I only need to assemble the driver and output transistor in place and then test all.

 

[wmac]

My amp serial number is 220080021. It refers to August 1980 and is the 21st unit produced that year. Now, my question is about the Flat-Amp: there are 2 Black Flag capacitors installed, marked 4pF (C15 and C16), but in the manual, they are 3pF. The manual had a factory revision, so it doesn't match what is installed. I replaced them following the manual.

 

[Hyperion]

replaced them following the manual

Generally you should work with what is in your unit now, NOT the manual. Your manual never had to work to spec as a functioning amplifier, your X1 with component values (as it left the factory) and 'as found' did, apparently for years.

In this particular case, as the value difference is so small, it shouldn't matter, buy hey, its an AU-X1 (Ultra High Speed DD/DC)

 

[wmac]

Generally you should work with what is in your unit now, NOT the manual. Your manual never had to work to spec as a functioning amplifier, your X1 with component values (as it left the factory) and 'as found' did, apparently for years.

In this particular case, as the value difference is so small, it shouldn't matter, buy hey, its an AU-X1 (Ultra High Speed DD/DC)

Thank you for all the information regarding the 2 black flag caps. They were installed after, in the back of the board, so that I may have mistaken them for C15/16 with those caps; they are not listed in the manual.

 

[wmac]

Thank you for all the information regarding the 2 black flag caps. They were installed after, in the back of the board, so that I may have mistaken them for C15/16 with those caps; they are not listed in the manual.

My statement is wrong, the ones that were installed in the back of the board were 2pF, and I replaced them with the same value, now the 4pF were in fact the C15/16 that I replaced with 3pF

 

[wmac]

Picture of the parts replaced in this unit:





The total number of parts replaced is 197 parts, that is:
115 Electrolitics Caps
4 Film caps
36 Black Flags caps
6 Trimpots
30 Transistors
6 Resistors

 

[wmac]

I need some help: 2 grey cables come from the power supply and go to the driver boards. Their positions on the power supply are pin 12 and pin 13. They will connect to the board F-2775 at position 16 on each side, but I am not sure whether 16 is the correct one; the schematic is not clear. I would appreciate it if somebody had the picture or could tell me if pin 16 is the right one.
Thank you

 

[Sui-Yogi]

I’m sure that someone is going to chime in here but in any case you can visit “amp 8” website with lots of high resolution photos.
Especially in AU-X1/X11 the “B -series “ and many others , he has a huge collection of restorations following high resolution photos .

 

[wmac]

I’m sure that someone is going to chime in here but in any case you can visit “amp 8” website with lots of high resolution photos.
Especially in AU-X1/X11 the “B -series “ and many others , he has a huge collection of restorations following high resolution photos .

Thank you, by the way, do you have his URL? I can not find him here.

 

[Sui-Yogi]

Here is a good one but there are more :

amp8.com/sansui/x-xx/x1/au-x1-8.htm

 

[wmac]

I believe I figured out that F-2781 pins 12 and 13 are the left/right power amp output lines going to the protection/speaker relay circuit, and should connect to Pin 16 at the F-2775.

 

[Hyperion]

I believe I figured out that F-2781 pins 12 and 13 are the left/right power amp output lines going to the protection/speaker relay circuit, and should connect to Pin 16 at the F-2775.

I think you'll find its F-2775 pin12 (R) and pin12 (L) that are the output lines going from F-2775 (R & L) to the output switching relays and protection circuit on F-2781. Pins 12 & 13 on F-2781 are the other part of the protection circuit, using sensing lines from F-2775 pin16 (R & L).

 

[wmac]

Well, after putting all back, set the DC Offset and Bias, I can not produce sound, the speaker relay will not click, I measured the DC Offset before the relay between pin 16 and ground, and I have 0.3 mV, the relay should engage, I believe that I still have a problem with the protection circuit, I will check.

 

[wmac]

The X1 is fixed. I am going to run some tests and post the pictures here.

 

[wmac]

This is the burn-in test; the sound of the video is not good. I was making the video with my phone and the amp connected to a $20 Walmart speaker

I don't know, they classified this video as age-restricted.

 

[wmac]

Heatsink temperature test, both sides:







This is after 2 hours of playing.

 

[Sui-Yogi]

So what was the problem ? Post#73

 

[wmac]

So what was the problem ? Post#73

The problem was in the protection circuit. took some time because I was waiting for parts, then I decided to work on a Trio KP-5050, which is already ready.

 

[wmac]

Finish the Sansui AU-X1. In the video, it is playing with a Trio KP-5050. The X1 is connected to a high-end pair of speakers that I bought at Walmart for $20. The sound is very good
Now going to restore the Pioneer M25

 

[wmac]

I bought another X1, but this one is very early production, April of 1979. I know that there is a service bulletin addressing the oscillation, but I can not find, I would appreciate if somebody has it and can share it.