skippy124 Posted September 9, 2012 Posted September 9, 2012 Hi, I am in the middle of restoring an AU717 that I acquired earlier this year, and I thought That this may be of interest to some SNA members. The AU717 is the at the high end of the AU"X"17 series. The series starts with the AU117, and goes through to the AU517, and then finally the AU717. The AU717 shares much of its design with the AU517 (for example Dual mono power supplies). It is rated at 85W per channel, 20hz to 20khz with no more than 0.025% THD, and weighs in just a tad under 18kg. The unit was acquired as not working, and without a base plate. It was in need of some TLC, as the faceplate and internals will attest. Top cover was removed, and I think there must have been a half a kilo of dust all over the internals (tone control and equalizer covers also removed) Close up of one of the main amp modules Close up of a corner of the Power Supply PCA The amp suffered some damage during transport, the chassis has been bent slightly where the transformers mount, however that will be takan care of during the restoration
skippy124 Posted September 9, 2012 Author Posted September 9, 2012 (edited) First thing to do was give the entire unit a basic clean with a small paint brush and vacuum cleaner, and then remove the two main amp modules for a check over, full clean and recap. The 717, like the 417 and 517 have easily removable main amp modules. The first thing to check are the fuse resistors, as I have indicated in previous threads on Sansui Amps, many have fuse resistors that give problems and should be replaced as a matter of course. Each main amp module has two 150 ohm fuse resistors, and they checked out as follows - Definitely in need of replacement!!!! As I was planning to do a full recap and also maintenance work such as removing the glue that was used to secure the larger PCA mounted caps, the amp modules were first stripped down for a clean. Boards separated from the heat sinks The output transistors were removed, and the then the transistor mounting bases also removed which allowed the heatsink to be fully separated from the PCA's (with the rear of the PCA's having been cleaned during the process. Note the heatsink compound, somewhat dry and in need of replacement The heatsink was then stripped of the mounting brackets, and all everything was given a good clean Edited September 9, 2012 by skippy124
skippy124 Posted September 9, 2012 Author Posted September 9, 2012 The PCA's were also given an good clean, and them the modules were re-assembled Output transistor sockets remounted Output transistors placed in position (not yet ready for final assembly, I wanted to check them before putting them back in with new mica insulators and thermal compound Outputs installed after all tested OK Next was replacing the fuse resistors, Existing fuse resistors New ones in place (taken after the caps were also replaced) Next on the list of things..... remove caps, remove glue and any affected components and replace caps
skippy124 Posted September 9, 2012 Author Posted September 9, 2012 Go man go! Brave and worthy project. Thanks!! Watch this space for updates on progress
SansuiGuy Posted September 9, 2012 Posted September 9, 2012 I admire your skills, great work! If only I had the ability to do this kind of work I would have saved a fortune in repairs and restorations over the yeas. Well done again, another classic Sansui back from the grave! 1
Sub Sonic Posted September 10, 2012 Posted September 10, 2012 Thanks for your efforts in posting rebuilds, they are great reading :-)
caddisgeek Posted September 10, 2012 Posted September 10, 2012 Great work, I'd love to have that level of skill and knowledge. Thanks for sharing
skippy124 Posted September 10, 2012 Author Posted September 10, 2012 Great reading keep it up... Love your work skippy ...amazing stuff I admire your skills, great work! If only I had the ability to do this kind of work I would have saved a fortune in repairs and restorations over the yeas. Well done again, another classic Sansui back from the grave! Thanks for your efforts in posting rebuilds, they are great reading :-) Great work, I'd love to have that level of skill and knowledge. Thanks for sharing Thanks for the comments, much appreciated nice work John Is this one a keeper? Hi Mark, Yes, this one is going into the collection when finished, now looking for an AU217 and an AU117II and Pete and I will have the complete series. Cheers John
skippy124 Posted September 11, 2012 Author Posted September 11, 2012 The glue used to secure the large caps tends to go hard over time and will affect components that it comes into contact with, fortunately the glue hadn’t damaged any components on the main amp boards Glue removed The electrolytic caps were replaced with a mixture of Nichicon HE, Panasonic FC and Panasonic stacked films were used for the 1uf caps. Next job was to get the power supply board out for inspection
skippy124 Posted September 11, 2012 Author Posted September 11, 2012 The power supply board was removed and once again the dreaded Sansui glue was evident, and there were quite a few components that had been damaged by contact with the glue The electrolytic caps were removed, and this revealed the full extent of the problems The glue had also run down the board in a couple of places, again causing problems with some components it came into contact with This is the diode pair that was removed in the photo above – note the corrosion The glue had also run down and around/under one of the fuse clips Once these components are cleaned they will be re-installed, plus 10 resistors will need to be replaced and all remnants of glue removed. Once this is complete new caps will be installed….. watch this space for more photos once this is done
skippy124 Posted September 12, 2012 Author Posted September 12, 2012 Amazing work mate. Cheers!! Some further progress has been made, the glue has been completely removed (needed to remove another set of fuse clips on the opposite of the board as the glue had run under these as well) Diode bridge has had the corrosion removed and a cot of clear protective laquer applied. And the glue around the fuse clips removed And to show the importance of removing any glue affected components - this rectifier diode is one of several that are spaced off the board with small ceramic tubes, this is what was hidden by one of these spacers and shows the effect the glue can have over time - The PSU board finally ready for caps to be fitted (there are still two bi-polar caps on the board, I don't have replacements for those at the moment, but a couple are one the way And the finished result More instalments to follow....
LogicprObe Posted September 12, 2012 Posted September 12, 2012 Great stuff Skip..............that amp looked near death at the start! That glue is certainly evil stuff! What solvent do you use to remove it? Or is it mechanical?
skippy124 Posted September 13, 2012 Author Posted September 13, 2012 Thanks LP I use a mechanical process to remove the glue, a strip of FR4 circuit board about 10mm wide with the end filed to a chisel shape, and this is used to scrape the glue off carefully. Then a final clean with isopropyl alchohol. Most solvents that will soften the glue will also take off the silk sceeening. The dried out dark brown glue usually comes off relatively easily, but the light brown glue that has not yet "gone off" can be time consuming to remove. Cheers John 1
Ahh- Schnoo Schnoo Posted September 13, 2012 Posted September 13, 2012 Once again a big thank you for posting your work. Very interesting, and really a labour of love. Your collection would be awesome to see Cheers
tagstrip Posted September 13, 2012 Posted September 13, 2012 I recall working on a Sansui AU 414 several years ago- superbly built, but that rotten glue was really annoying. I used Shellite to help get the gunk off, but it seemed to take an age! I replaced all the electro caps bar the main two big P.S. ones -then Shock, Horror!- modded the main power amp boards to improve the subjective sound quality! Needless to say, my customer who asked me to do just that, was stunned at the improvement! Another happy customer! But boy, what a Wagnerian effort is was to get it there- dunno if I would want to do another in a hurry! So hats off to Skip for tackling the job- I think your work looks a little neater than my effort was.
skippy124 Posted September 13, 2012 Author Posted September 13, 2012 Thanks for the comments!! I think it might have been a 417 that you worked on tagstrip - very similar to the 717, a little less watts out and a single power supply rather than the dual mono that the 517 and 717 features. A little more progress....... I am waiting on a couple of caps to finish off the power supply board before I can start to put her back together, so tonight I had a go at the front panel.... Just a reminder of what it originally looked like Well it wasn't much cleaner behind the front panel either..... A clean of the panel and the knobs and lever switch covers, and she is back together again I hope to have her back together again over the weekend, and will hopefully post up some final pics and some performance test results. Cheers John 1
pete_mac Posted September 13, 2012 Posted September 13, 2012 Much better! That cleaned up great. I had better hurry up and drop over those Muse bipolars for the power supply board!
tagstrip Posted September 14, 2012 Posted September 14, 2012 Ah yes, John you were right- it was a 417 I worked on a while back. I must be getting all lysdexic in my old age as eye carnott rumembah numbizz! When you look at the great build quality of this series Sansui's it makes you wonder "What wuz they thinking wiv all that gloo everywhere!" Talk about spoiling the ship (although very slowly) for a harp'orth of tar!
lebowski Posted September 14, 2012 Posted September 14, 2012 wow John, that has come up a treat. Lovely work and thanks for sharing
Sub Sonic Posted September 14, 2012 Posted September 14, 2012 Skippy, I have an apology to make, I accidentally rated this topic with 4 stars instead of 5 due to fumbling fingers pressing the wrong spot on the IPod! Your rebuilds definitely rate the full 5 stars!!!!! Regards, SS
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