Originally Posted by
Pars
Nice job cleaning it up/refurbing. Man, those phenolic boards look nasty; always hated those things.
Thanks.
That glue that Sansui used is both corrosive and eventually can co conductive over time.
First order of business is to remove all components touching the glue and assume they are bad or will soon fail. In fact, after removal all the glue tainted parts I removed were corroded to some degree, and many fell apart when removed.
Once the board has been vacated of parts you then have to clean off the glue, which generally involves several applications of acetone to soften the glue and careful but thorough scraping to achieve COMPLETE removal. It was a tedious process, and the rebuild of the power supply alone spanned two evenings.
On the PS alone, including the approximately 39 or so capacitors that needed changing, the defective parts total was 64 or so components. Most all the rectifier diodes, the protection relay/diode/transistor, several plain diodes, and a handful of resistors and other small signal transistors were all partially corroded. Of course the power regulator transistors and zener's, too.
All that remains now is to remove and replace the main filter caps ($25 each
). Once that's done I'll replace the DC offset and bias pots, do the final adjustments, and button it up.
This AU-717 sounds pretty sweet right now, and I look forward to many years of listening enjoyment out of it. It is a beast, but in a very good way.
