Audiomania
Active Member
Please repost photos.Thanks
Leestereo's Restoration/Upgrade Of A Sansui AU-717
- Thread starter Leestereo
- Start date
Audiomania
Active Member
Added chrome extension works great,Thanks
Hi to all members, this is my first post and I’m totally new to this world, though I’ve been following this site for sometime now. I’ve read this thread with great interest and have searched the web for all the technical information on this amp.
I have a doubt about the green Mylar caps on the F-2663 board, specifically the c28 & c27 caps which are rated 0.047, but what is the voltage rating for it?
I apologies for my English and thanks for any help.
I have a doubt about the green Mylar caps on the F-2663 board, specifically the c28 & c27 caps which are rated 0.047, but what is the voltage rating for it?
I apologies for my English and thanks for any help.
I believe the originals may have been 160V, they'll never see anything like that voltage which I think is chosen for reliability and stability. You can use 250V if you want, but watch the size (lead spacing) of any replacement as you might have trouble fitting them on the board if they are significantly bigger than the originals.
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SansuiJavier
Active Member
Good morning and thanks to all for the collaboration, a clarification please, on the board of equalization 2723 Lee says:
The 4 electrolytic capacitors are removed without jumpers in their place and the two 4.7 uF are simply placed instead of C35 and C36?
Thanks and excuse me if it is a beginner's question ... but I am finishing the complete restoration and everything is going great !!
The 4 electrolytic capacitors are removed without jumpers in their place and the two 4.7 uF are simply placed instead of C35 and C36?
Thanks and excuse me if it is a beginner's question ... but I am finishing the complete restoration and everything is going great !!
The basic principle is that if you have replaced 2 back to back electrolytics with 1 film capacitor, you are unlikely to need the film bypass capacitor which can be removed. And in this case, probably due to lead spacing constraints Leestereo (whose actual name is Ben incidentally), uses the film bypass location for the single replacement film capacitor. (no jumpers needed).
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Goldie99
Super Member
That's how I understand it from the schematic - so remove C27, C29, & C35, and fit a single new 4.7uF film in the C35 position; similarly for the other channel. Jumpers should not be fitted - they'd bypass the new caps.
SansuiJavier
Active Member
Thank you very much for your response, Hyperion and Goldie99, my doubt is clarified. 
Leestereo
Super Member
... but I am finishing the complete restoration and everything is going great !!
Happy to hear that your restoration/upgrade is relatively painless; looking forward to hearing your thoughts on how your "new" 717 sounds!
SansuiJavier
Active Member
Thank you Ben, and also John for your help. I finished the restoration right now (it's almost 2 in the morning here), the process took me about 3 weeks, in my spare time, the unit was working properly when I started, although the sound was not as good as I expected from a amplifier like that.
Now it's another world. After the restoration the sound is much clearer, more spacious and with much more stereo image. The bass, before were strong but with little definition, now they are much more forceful and precise. The sound in general is much more detailed. I love how it sounds. Tomorrow I will be able to hear it at a higher volume and I will try different speakers. But I am happy with him now, and with his spectacular sound.
As it is usually advised in these cases, I restored the amplifier in parts, I reassembled it to test it and went on with the next one. I have followed the instructions of Leestereo everywhere (I have to change the trimpots of board 2721 and 2722 that I asked wrongly), but it is an easy change that I will make in the coming days, this has not prevented me from adjusting the bias and DC without difficulty to the specifications.
When I had it mounted and working I noticed that the potentiometer of the volume turned harder and harder until finally it was blocked, I thought that all the work restoring the amplifier had not been for anything, I know that this potentiometer is impossible to obtain as a replacement if it fails in a unit.
Fortunately I found a thread that talked about this possibility and how to solve it, I did it and it works perfectly again, but I was really scared with the possibility of losing all the work and this lovely amplifier by the volume potentiometer. Here is the thread in case the same thing happens to someone:
http://audiokarma.org/forums/index....919-sticking-volume-pot.754547/#post-11028927
My sincere thanks to all those who have helped me, Ben and John, thank you very much.
Here the last photos of the more than 100 that I took:
Now it's another world. After the restoration the sound is much clearer, more spacious and with much more stereo image. The bass, before were strong but with little definition, now they are much more forceful and precise. The sound in general is much more detailed. I love how it sounds. Tomorrow I will be able to hear it at a higher volume and I will try different speakers. But I am happy with him now, and with his spectacular sound.
As it is usually advised in these cases, I restored the amplifier in parts, I reassembled it to test it and went on with the next one. I have followed the instructions of Leestereo everywhere (I have to change the trimpots of board 2721 and 2722 that I asked wrongly), but it is an easy change that I will make in the coming days, this has not prevented me from adjusting the bias and DC without difficulty to the specifications.
When I had it mounted and working I noticed that the potentiometer of the volume turned harder and harder until finally it was blocked, I thought that all the work restoring the amplifier had not been for anything, I know that this potentiometer is impossible to obtain as a replacement if it fails in a unit.
Fortunately I found a thread that talked about this possibility and how to solve it, I did it and it works perfectly again, but I was really scared with the possibility of losing all the work and this lovely amplifier by the volume potentiometer. Here is the thread in case the same thing happens to someone:
http://audiokarma.org/forums/index....919-sticking-volume-pot.754547/#post-11028927
My sincere thanks to all those who have helped me, Ben and John, thank you very much.
Here the last photos of the more than 100 that I took:
jwjarch
New Member
Hello All,
I’m working on an au-717 as well. For the equalizer board f-2723, has everyone worked on the board in place or do you take it out completely? Seems you would have to either de-solder the wires for the RCA inputs or try to get the RCA input boards out along with the f-2723. I’m just looking to know what the easiest/best way is to work on this particular board.
Also, there doesn’t seem to be much talk of replacing transistors in this amp. Are they pretty stable for the most part?
I’m working on an au-717 as well. For the equalizer board f-2723, has everyone worked on the board in place or do you take it out completely? Seems you would have to either de-solder the wires for the RCA inputs or try to get the RCA input boards out along with the f-2723. I’m just looking to know what the easiest/best way is to work on this particular board.
Also, there doesn’t seem to be much talk of replacing transistors in this amp. Are they pretty stable for the most part?
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SansuiJavier
Active Member
If you are also going to restore the board F-2670 (pre-main switch) it may be convenient to remove it completely, in my case I did not do it because I did not touch this F2670 card. In addition, the plastic fasteners that hold the RCA and pre-main input cards can easily break, you should replace them. In my case I preferred not to do it, you can work easily without removing it.
Just disengage the switch shaft, (by removing it), and remove the chassis brackets - also loosening the rear panel RCA connectors helps, (be careful not to strain the black ribbon cables), then work with the board in situ. If you have the driver assemblies removed, then so much the better.
Leestereo
Super Member
My preference is to work on the boards in situ whenever possible; the only boards in the AU-717 which were removed during the restoration/upgrade were the driver boards and the pre-main switch board (the plastic fasteners are coated with a sealant that can be dissolved with an ethyl acetate solution e.g., non-acetone nail polish remover).
SansuiJavier
Active Member
I understand that the 2SA726 and the 2SA906 can have problems sometimes, but I have not changed them in mine ... they advised me not to change the transistors if they do not give problems or are noisy
jwjarch
New Member
Wanted to thank Ben and everyone that has contributed to this thread over the years. It's really making the restoration of my friend's AU-717 a breeze.
As soon as I opened the unit I knew it was a total redo. The goal is to give my friend back a dependable unit that doesn't have any funny business going on in terms of band-aid fixes. A previous tech had done some repairs to keep the unit running; repairs I did not agree with. You can see the photos of some 2,200uf caps installed to "by-pass" the main caps that were on their last legs (one cap was clearly bulging and I couldn't even get a reading with my capacitance meter). I replaced those with KEMET ALT22's, 15,000uf 63V. A steal at $6 a piece from Mouser. I also replaced the 2.2uf/100V film by-pass caps with new Panasonic ECQ-E films while I was at it.
Board F-2663 is almost redone. I had the usual glue damage which unfortunately also spread to the 2SC1708 transistors, TR09 and TR10 near C09 and C10. I went ahead and replaced all four 2SC1708 with KSC1845's (matched HFE). I also had a few resistors fall apart on me when I removed them from the board. The original speaker protection relay had been removed and replaced with a 48V Omron that was siliconed in between the driver boards. What the?!?!? AND, whoever did that, did some damage to the board.
Luckily the pads were not compromised and I was able to clean it up and solder in the new Omron relay. As per Ben's guide I replaced the 10K and 22K resistors, the VD1212 diode, as well as the ZD01-ZD02 zeners which were also covered in glue. After all that I took the time to clean all the old flux off the board with denatured alcohol. It really looks better than new! Last is to solder in the 820uf caps, C05-C08. The first 820uf Panasonic FS caps I ordered were too tall for the space. Doh! Make sure you pay attention when ordering! The new Nichicon PW caps should be waiting for me when I get home tonight.
So...., so far, so good. I'm hoping to get those caps in and test the power section before moving on to the driver boards next. I'm planning to do the tone board after that and the EQ/phono board last. Fun stuff! And thanks again for this amazing resource!
As soon as I opened the unit I knew it was a total redo. The goal is to give my friend back a dependable unit that doesn't have any funny business going on in terms of band-aid fixes. A previous tech had done some repairs to keep the unit running; repairs I did not agree with. You can see the photos of some 2,200uf caps installed to "by-pass" the main caps that were on their last legs (one cap was clearly bulging and I couldn't even get a reading with my capacitance meter). I replaced those with KEMET ALT22's, 15,000uf 63V. A steal at $6 a piece from Mouser. I also replaced the 2.2uf/100V film by-pass caps with new Panasonic ECQ-E films while I was at it.
Board F-2663 is almost redone. I had the usual glue damage which unfortunately also spread to the 2SC1708 transistors, TR09 and TR10 near C09 and C10. I went ahead and replaced all four 2SC1708 with KSC1845's (matched HFE). I also had a few resistors fall apart on me when I removed them from the board. The original speaker protection relay had been removed and replaced with a 48V Omron that was siliconed in between the driver boards. What the?!?!? AND, whoever did that, did some damage to the board.
Luckily the pads were not compromised and I was able to clean it up and solder in the new Omron relay. As per Ben's guide I replaced the 10K and 22K resistors, the VD1212 diode, as well as the ZD01-ZD02 zeners which were also covered in glue. After all that I took the time to clean all the old flux off the board with denatured alcohol. It really looks better than new! Last is to solder in the 820uf caps, C05-C08. The first 820uf Panasonic FS caps I ordered were too tall for the space. Doh! Make sure you pay attention when ordering! The new Nichicon PW caps should be waiting for me when I get home tonight.So...., so far, so good. I'm hoping to get those caps in and test the power section before moving on to the driver boards next. I'm planning to do the tone board after that and the EQ/phono board last. Fun stuff! And thanks again for this amazing resource!
