Absolutely +1
With Jomark's really in-depth knowledge of Sansui, and the eternally positive attitude of OJ - who could want for more...
Not forgetting the fantastic help I have had from you Ron
and Harold. 
Absolutely +1
With Jomark's really in-depth knowledge of Sansui, and the eternally positive attitude of OJ - who could want for more...
Not forgetting the fantastic help I have had from you Ron
and Harold.
It's fine Willy6 really, but for you reading the progress of your own restore, it will be so much better.
Time for an update.
I haven't been taking as many pictures as I perhaps should have, but with a job this testing (for me anyway) I just get wrapped up in it and forget.
This is the finished 'Muting' PCB. F-2773
This is the nearly complete 'Flat Amp' F-2819. note the use of a single bipolar 'Muse' capacitor (green) to replace 2 back-to-back polar capacitors, and the other position shorted with a link.
And now on to the Protection PCB F-2781 - this is untouched.
I found this on the underside, 330µF 16V across the 470µF 10V timing capacitor on the topside.
And Protection PCB finished. (need to re-dress the wiring).
A number of trials and tribulations overcome along the way, such as:-
Temporary short on both -11v supplies, caused by star ground solder tag bent to wrong position.
Cannot set Flat Amp DC offset on one channel, caused by misplaced trimmer leg.
No relays firing on the Protection PCB, caused by substitute relay driver and series regulator pass transistors mysteriously not functioning, changed for different sub, all OK.
I have now 'touched' all the electronics of the amplifier. I have checked for any sign of instability with an oscilloscope - none found, so I think I am ready to re-install the output transistors and run some tests.
I haven't been taking as many pictures as I perhaps should have, but with a job this testing (for me anyway) I just get wrapped up in it and forget.
This is the finished 'Muting' PCB. F-2773
This is the nearly complete 'Flat Amp' F-2819. note the use of a single bipolar 'Muse' capacitor (green) to replace 2 back-to-back polar capacitors, and the other position shorted with a link.
And now on to the Protection PCB F-2781 - this is untouched.
I found this on the underside, 330µF 16V across the 470µF 10V timing capacitor on the topside.
And Protection PCB finished. (need to re-dress the wiring).
A number of trials and tribulations overcome along the way, such as:-
Temporary short on both -11v supplies, caused by star ground solder tag bent to wrong position.
Cannot set Flat Amp DC offset on one channel, caused by misplaced trimmer leg.
No relays firing on the Protection PCB, caused by substitute relay driver and series regulator pass transistors mysteriously not functioning, changed for different sub, all OK.
I have now 'touched' all the electronics of the amplifier. I have checked for any sign of instability with an oscilloscope - none found, so I think I am ready to re-install the output transistors and run some tests.
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Ronito6
Super Member
Did you exchange the cap below for new or upgraded the one on the other side / top side of it?
Also, any info on the caps you used to replace the four big 25v 4700 originals on the 2781 power protection board?
Finally, I noticed that you replace a couple of diodes on the 2781 board. Info please?
Also, any info on the caps you used to replace the four big 25v 4700 originals on the 2781 power protection board?
Finally, I noticed that you replace a couple of diodes on the 2781 board. Info please?
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Ronito6
Super Member
Oh yeah...forgot to ask...
Any details possible on the Kuehne ground modification?
More details on this and its effects would add quite a bit to the X1 knowledge base.
AND
"Temporary short on both -11v supplies, caused by starground solder tagbent to wrong position"
Any chance of pics and details of this problem and its solution?
THANKS!!
Any details possible on the Kuehne ground modification?
More details on this and its effects would add quite a bit to the X1 knowledge base.
AND
"Temporary short on both -11v supplies, caused by starground solder tagbent to wrong position"
Any chance of pics and details of this problem and its solution?
THANKS!!
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I replaced these capacitors - the 470µF (topside) and the 330µF shown below like for like - the underside 330µF is now much smaller, more neatly soldered and positioned. Replacing with one capacitor ?? - who has 800µF (or 820µF) capacitors 'on hand'
Choices fairly limited for these - I eventually used Nichicon HE, 4700µF 25V replacements, and fitted some foam padding under each one for support, as the lead spacing wouldn't allow them to be flush to the board.
I changed both zeners, and all the other smaller glass diodes including the MV12 replaced with the usual series pair of 1N4148's
I am ashamed to say that I lifted one pad when replacing components on the protection PCB, thankfully this is a rare event for me.
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I performed the modification to the Flat Amp board almost exactly as shown by Harold with his 3 stage picture of how it should be done. The capacitor between the grounds on the Flat Amp, I connected right on the signal ground posts (at the end of the Flat Amp PCB), and then used thick stranded wire to connect the additional 2 capacitors to the earth tag - the now infamous tag described in the '-11V problem' in the quoted post from Ron below.
The way I see it, when you have grounds on PCB's in a fast amp like this, they have to be connected in as close to a 'star grounding' system as possible, or otherwise in a series fashion to a central point to avoid ground loops. Inevitably noise 'pickup' from various sources inside and outside the amp will cause some grounds to be noisier than others which, with the high gains and extended frequency response present, this could (and does!) cause instability. The choice of decoupling capacitor 'value' and 'dielectric' is very important here, and I think the choice of 10nF (10,000pF) capacitors is indicative of the high frequencies being dealt with by this modification. The installation of three capacitors, one to effectively short the Flat Amp grounds together at high frequencies, and 2 more to shunt both Flat Amp grounds to a star ground, is unusual in my experience, but I believe I can understand why it was done this way, even though the Flat Amp is already DC grounded.
AND
"Temporary short on both -11v supplies, caused by star ground solder tag bent to wrong position"
Any chance of pics and details of this problem and its solution?
THANKS!!
Not a lot to see or describe really, I had bent the tag, (located on the chassis member in between the driver amp modules and the phono amps), upwards to tighten the screw I think? - and had forgotten to bend it down again. This meant that when I re-installed the phono amp boards 2 of them shorted on this tag and caused the problem. 2 minutes to find the problem and 30 seconds to reform the tag - done.
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Ronito6
Super Member
Leestereo
Super Member
I replaced these capacitors - the 470µF (topside) and the 330µF shown below like for like - the underside 330µF is now much smaller, more neatly soldered and positioned. Replacing with one capacitor ?? - who has 800µF capacitors 'on hand'
Just for future reference, note that 820µF is a standard value; Mouser stocks this size with 3.5mm, 5.0mm and 7.5mm lead spacing variants: http://www.mouser.com/Passive-Compo...Z1z0yoh6Z1yx4aw3Z1yqjoa3Z1yx4awy&Ns=Pricing|0
Thanks Lee, I am aware it is a standard E24 value, but I just don't have one 'on-hand', finding that 330µF under there was a 'Sansui special' surprise - I have most values up to 470µF, but not 820µF, I also only buy 1000µF when I need them, BTW - there are 14 of these in the AU-X1. 
- I have most values up to 470µF, but not 820µF, I also only buy 1000µF when I need them, BTW - there are 14 of these in the AU-X1.
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Update: With the sacrificial OP transistors still installed (1 pair per channel), I get output, only testing at very low levels at present - controls and switching seem to work, sine wave output looks fine, and a beautiful square wave output albeit at 1kHz, that you could chop parsley with
Next steps
Try frequencies up to 20kHz.
Then back the bias down, so it reads just a 'sniff' of bias.
Remove output modules and re-fit original OP transistors, refit modules.
Adjust DC offset, re-adjust bias and perform same tests.
Next steps
Try frequencies up to 20kHz.
Then back the bias down, so it reads just a 'sniff' of bias.
Remove output modules and re-fit original OP transistors, refit modules.
Adjust DC offset, re-adjust bias and perform same tests.
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Thanks Tom, this has been quite a testing project for me, had to 'pull out all the stops' so to speak. - however, I remain in the shadow of Harolda's and Ronito's restores, and have been helped tremendously by both.
There are still a number of problems to surmount if I want to go the whole distance - like the 8 x 10000µF main smoothing capacitors - nothing of the correct size available now. (all seem to be ~50mm diameter, but really need 40mm diameter). I have a solution for the 2 smaller dual 2200µF can capacitors (re-stuff), however, restuffing options are severely limited if not impossible for the bigger ones.
Anyway the 'can capacitors' are 'phase 2' - I want to get 'phase 1' done and have a good listen
That's all for now.
- however, I remain in the shadow of Harolda's and Ronito's restores, and have been helped tremendously by both.There are still a number of problems to surmount if I want to go the whole distance - like the 8 x 10000µF main smoothing capacitors - nothing of the correct size available now. (all seem to be ~50mm diameter, but really need 40mm diameter). I have a solution for the 2 smaller dual 2200µF can capacitors (re-stuff), however, restuffing options are severely limited if not impossible for the bigger ones.
Anyway the 'can capacitors' are 'phase 2' - I want to get 'phase 1' done and have a good listen
That's all for now.
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