Discussion in 'Exclusively Sansui' started by Hyperion, Mar 16, 2018.
That board is a work of art sir.
Really nice work John !
The amp is in good hands, keep it going .
The use of the short and fat electrolytics is much appreicitated, this area gets covered by the flat metal panel that there is hardly any space for airflow .
I believe there are couple of holes in the left and right chassis but this section of the amp gets heated easily due to restricted air flow.
It seems I have been remiss, judging by the reception my post with the pictures got, I must post more!
Thank you all for the appreciative comments and likes.
John, as my amp work has stalled (with three AU-X11 in the to-do list) I'm living vicariously through you. More nudes please!
LOL - I see what I can do.
I got the second of the 2 driver assemblies completed yesterday, today I installed it and powered the amplifier on for a check of DC offset & bias after many component changes. On DBT (and step-down) for first power up of course - all fine, so switched to full mains (via step down transformer). And it checks out as expected.
I make that:-
Next up:- the Flat Amp and the Interconnect PCB.
Nicely done. I have one of these here to do myself. Should be a fun one
One thing I noticed was the same issue I faced on the AU-X1 - which is the inability to set the +/- 11V output of the regulators on the main regulated PSU. One allowed a maximum of +/-10.32V and the other was +/- 10.45V - I will make the same changes on this X11 that I performed on my own X1 to make this possible, I changed R17, 5.6KΩ to 3.9KΩ in two positions on F-3463 PSU which worked very nicely.
I got the Flat Amp completed, the Interconnect Board relay made up and installed, and the M Kuehne Flat Amp stability mod installed (just in case). Switch cleaning done and careful re-installation of the Flat Amp//Interconnect Board combination now in progress, I just need to install the Flat Amp trimmers (on the track side of the board). A blown indicator bulb has been replaced, and the resistor value changes on the Main Regulated PSU are complete.
I think I'm going to give it a listen before the last main job which is the PSU/Protection board, one of, if not the most, difficult boards in the whole amplifier. (for the vast number of connections to it, too many being soldered and not plug & socket).
Here is a picture of the Flat Amp, and below it the Interface Board before any component changes, Above you can see the sleeved resistors on the Regulated PSU.
And another of the re-assembled front panel, you can just see the track side mounted Bourns trimmers showing just peeping up above the lower edge of the large opening. Now you can see the reason why I was very keen to have those PSU resistors sleeved. Note the cable-form stretching from left to right, reducing in groups of three as they find their connection points on the regulated PSU, running very close to those resistors.
Note also the use of a spare (White) LED in the protection light socket to the left - so I can see it flashing and going steady while I check things over. (Note the standard protection LED is glued to the front panel as with many Sansui's - and sometimes you need to work without the front panel installed).
I have been able to adjust the +/-11V spot on now, and the Flat Amp is very quiet and has very low DC offset drift - pleased with that.
Those pictures do make one wonder how Sansui managed to continue to produce amps such as this with the amount of manual labor involved, the level of assembly detail makes me think of the original stereo tube amplifier manufacturers in the early 60's.
Will be interesting when you run it up against your 919 sir.
I'm pretty sure it will be close, I still have in my memory how marvellous AK member Multimode's AU-919 turned out after I had finished it, it was noticeably better than my own! This is my next project (among many) to perform some of the same tweaks to my AU-919 learned here from you clever lot out there in AK Internet land.
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