Sansui au-517 balance test

The Fuxtor

Addicted Member
Hiya , sold one of these to my buddy , but soon after he complained that one channel sounded weaker then the other. Headphones were even more distinct... Fast forward to now: Deoxit of balance pot, volume pot and all switches and even bass / treble pots.Replaced preamp transistors ( unit was balanced as a power amp ) and bathed the loudness switch. OK..... to my ears this unit sounds awesome and very equal one channel to the next. I dont know if he has some golden ears , but i would certainly be happy reowning it at this point!
My big question is how can i test this using a multimeter to assure him that all is good? My thoughts would to run a signal generator as a source and measure each speaker output with the meter set to Acv ?? would this be an accurate measurement for comparison??
Charles
 
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My big question is how can i test this using a multimeter to assure him that all is good? My thoughts would to run a signal generator as a source and measure each speaker output with the meter set to Acv ?? would this be an accurate measurement for comparison??

Yes that would work, I typically use a signal generator with bridged output into the amp. Then with dummy loads on the speaker outputs I use two scope traces to verify both channels are equal (my scope also displays ac voltage in real time which helps). You can achieve the same results by using the ac function on your multimeter. Note that those 40 year old balance and volume potentiometers may not be tracking 100% left to right which would throw off the voltages slightly. This also can be addressed through selective board level component modification but is a royal pita to accomplish, most folks just tweak the balance control slightly, in fact I have to leave my units permanently set a click left from center to counter hearing loss in one ear.
-Lee
 
snip---
My big question is how can i test this using a multimeter to assure him that all is good? My thoughts would to run a signal generator as a source and measure each speaker output with the meter set to Acv ?? would this be an accurate measurement for comparison??

Yes that would work, I typically use a signal generator with bridged output into the amp. Then with dummy loads on the speaker outputs I use two scope traces to verify both channels are equal (my scope also displays ac voltage in real time which helps). You can achieve the same results by using the ac function on your multimeter. Note that those 40 year old balance and volume potentiometers may not be tracking 100% left to right which would throw off the voltages slightly. This also can be addressed through selective board level component modification but is a royal pita to accomplish, most folks just tweak the balance control slightly, in fact I have to leave my units permanently set a click left from center to counter hearing loss in one ear.
-Lee
Ok, cool! Thank you!
 
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