Re: Sansui AU-717 - Circuit Protection Delay

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Posted by bluelite on October 06, 2003 at 09:24:43:

In Reply to: Sansui AU-717 - Circuit Protection Delay posted by Richard Newman on October 06, 2003 at 04:35:14:

I have a AU-717 that exhibited nearly the same symptoms before it finally would not engage its protection relay at all. It currently sits double-boxed awaiting shipment to a trusted repair tech.

My research on possible causes for the problem showed several possibilities, all beyond my limited knowledge and experience to correct.

The explanation that made the most sense in my case involved the glue that holds the capacitors and other various parts tight to their respective boards. It seems that over the years (25?) this glue becomes somewhat conductive and injects a small amount of direct unfiltered current between contacts of the capacitor or the various other electronic parts it comes in contact with. The protection circuit will not allow the relays to engage as long as the DC current exists. Looking on the boards, its appearance is like the hot glue used in making crafts. The cure is to take out the boards and remove the glue.

Otherwise it may be dried out or blown capacitors. Bad capacitors may be easy or difficult to spot. An obvious brown colored leakage around the base of the capacitor is a dead giveaway. Also if the top is “popped” up or the barrel is swollen the capacitor is likely bad. A dried out electrolytic capacitor is hard to detect and potentially dangerous to try and find.

More difficult to detect is a bad transistor. A post on a previous Sansui message board (no longer up) claimed a transistor which looked like a “firecracker” would go bad on the amp modules and needed to be replaced if this delayed engagement condition occurred. I am still trying to figure out which transistor he meant.

I am not a tech and have just enough knowledge to hurt myself or destroy my amp if I muck around in there. So I will send mine off for repair.

Good luck with yours. Let us know when you get it running what the problem was.

: I have one of these beasts and would not use anything else. However, lately the circuit proection light blinks for up to a minutes before it finally lights up. Can anyone give any advice as to why this happens?

: Also, my AU-717 is an American model (I live in the UK) and I'm having difficulty in finding replacement fuses to go in the fuseholder on the back panel. Can anybody let me know where these can be obtained.

: Thanks - I look forward to any advices.

: And what a great site !!!

: Richard Newman

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