Restoring a Sansui AU-X1

[Hyperion]

It's an offset adjustment, the Service Manual (page 11, section 4.3) says measure the voltage at TP01 on F-2917/18 while adjusting for 0V. It is balancing the value of R35 (510Ω) and VR01 (100Ω) with the value of R34 (560Ω), as I understand it, adjusting the current through D01 & D02 and thereby the voltage across them. The trimmer is being used in it's simplest way as a variable resistor, as opposed to a 'potential divider', so either Ω value should work.

 

[wmac]

It's an offset adjustment, the Service Manual (page 11, section 4.3) says measure the voltage at TP01 on F-2917/18 while adjusting for 0V. It is balancing the value of R35 (510Ω) and VR01 (100Ω) with the value of R34 (560Ω), as I understand it, adjusting the current through D01 & D02 and thereby the voltage across them. The trimmer is being used in it's simplest way as a variable resistor, as opposed to a 'potential divider', so either Ω value should work.

Yes, I got confused as to why they changed to 250 Ohms. I will replace it with a 100 Ohm pot. Thank you

 

[Hyperion]

Good idea, then you can find out if there was a reason for the altered value trimmer - obviously we can help you work that out when the time comes.

 

[wmac]

Good idea, then you can find out if there was a reason for the altered value trimmer - obviously we can help you work that out when the time comes.

I will replace the trimmer, but I need to first finish the restoration on the front to put all back together and test. By the way, you were right about R36 and R37 on the F-2775 board; they were open.

 

[wmac]

This project is on hold now. I received the tool but could not remove the screw, not even by heating the knob. Next week I will take it to a place they have diffrent tools, maybe they will take it out.

 

[Hyperion]

What about heating the allen key, an all metal standard one.

Heat it up, wrap the cold end with some tape so you can hold it, insert it into the allen screw in the knob and leave it like that for a minute or so. Then have a try with your new tool?

The idea being to heat the screw and break its bond with the thread in the knob.

Otherwise put some penetrating oil on it and leave it for a few days, before trying again to loosen it.

 

[PE9ZZ]

If you have space in your freezer put the whole amp in it overnight. Most metals shrink with temperature. Works wonders with stuck harddisks.

 

[Sui-Yogi]

If you have space in your freezer put the whole amp in it overnight. Most metals shrink with temperature. Works wonders with stuck harddisks.

Interesting!!!!

 

[Hyperion]

I always knew the AU-X1 was a cool amplifier!

 

[wmac]

What about heating the allen key, an all metal standard one.

Heat it up, wrap the cold end with some tape so you can hold it, insert it into the allen screw in the knob and leave it like that for a minute or so. Then have a try with your new tool?

The idea being to heat the screw and break its bond with the thread in the knob.

Otherwise put some penetrating oil on it and leave it for a few days, before trying again to loosen it.

This is the last thing I am going to try. Maybe somebody put some thread lock in it.

 

[wmac]

@Hyperion Thank you for the tip, finally I got it out

 

[wmac]

Here is where we are:








Almost finished, need to receive some 0.22uF Film Caps and 2 and 4 pF ceramic, then I can start to mount back test and calibrate.

In the meantime, I will try to finish my Luxman L-560, because the parts will take about 10 days to get here.

 

[wmac]

Just received the missing components to finish, now it is time to assemble it back again.

Of the 33 black flag capacitors, none of them measure up to the specifications.

 

[Hyperion]

It doesn't look like you are replacing the trimmers on the Flat Amp? - (last picture in post #52). I think you should replace all the trimmers, no exceptions.

 

[wmac]

It doesn't look like you are replacing the trimmers on the Flat Amp? - (last picture in post #52). I think you should replace all the trimmers, no exceptions.

You are right, I don't have the trimmers for that position. I will check if I can find I will do it

 

[Hyperion]

You are right, I don't have the trimmers for that position. I will check if I can find I will do it

IIRC in stock form they are adjusted from the track side. If you choose a 'top adjust' trimmer replacements it is possible to adjust them from the (top) or component side.

 

[wmac]

The pot is 50K, which I don't have in stock. If I can find them locally, I will replace them.

 

[Hyperion]

The pot is 50K, which I don't have in stock. If I can find them locally, I will replace them.

The Flat Amp trimmers are 100Ω

 

[wmac]

You are right, 2 pots are 100 ohms VR01 and VR02, and 2 that are 50K VR101a and VR101b. I will replace them tomorrow

 

[Hyperion]

You are right, 2 pots are 100 ohms VR01 and VR02, and 2 that are 50K VR101a and VR101b. I will replace them tomorrow

I think VR101a & b is the volume control?
Actually VR701a & b