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Sansui QS-1

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Soundfield

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Those transistors with resistors inside are called RETs (Resistor Equipped Transistors) - you can buy them from most hobby stores...
The only RET s I've seen are just a couple of undedicated transistors with bias resistors-
RET.JPG

whereas the Sansui modules are rather more complete, specific circuits that have been encapsulated (in fact Sansui give them the circuit designation of "IC")-
sansui ic.JPG
 

par4ken

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I have an old Sansui QS1 that has a bad hum if anybody wants it and will pay for shipping hey can have it
A bad hum is usually caused by bad filter Capacitor(s) in the power supply. Given the age of this vintage equipment it's amazing that any of it still works. I've replaced a lot of capacitors in old equipment mainly in an effort to get better sound, only occasionally actually finding a bad one. A bad capacitor will cause some sort of fault, such as this. I've seen more bad capacitors in newer equipment, than in 70's stuff. I guess the Chinese don't have the right capacitor recipe to make things last.
I'm tempted to take it off your hands, but I don't really need another one. The chassis could be used as the base for a quad preamplifier just add an involve evaluation board. The unit has everything volume balance, switching and really cool looking meters.
 

chucky3042

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A bad hum is usually caused by bad filter Capacitor(s) in the power supply. Given the age of this vintage equipment it's amazing that any of it still works. I've replaced a lot of capacitors in old equipment mainly in an effort to get better sound, only occasionally actually finding a bad one. A bad capacitor will cause some sort of fault, such as this. I've seen more bad capacitors in newer equipment, than in 70's stuff. I guess the Chinese don't have the right capacitor recipe to make things last.
I'm tempted to take it off your hands, but I don't really need another one. The chassis could be used as the base for a quad preamplifier just add an involve evaluation board. The unit has everything volume balance, switching and really cool looking meters.
Or a busted ground connection around the RCA's
 

Soundfield

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Looks as though Sansui always had a ground loop hum problem with the QS-1 as the service manual contains the following modification-
f1.JPG

and rather more desperately-
f2.JPG

although of course aluminium wouldn't have provided any shielding against magnetically induced mains hum!
 

Sonik Wiz

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Looks as though Sansui always had a ground loop hum problem with the QS-1 as the service manual contains the following modification-
View attachment 57579
and rather more desperately-
View attachment 57580
although of course aluminium wouldn't have provided any shielding against magnetically induced mains hum!
That's pretty interesting. I did not have a hum problem with my QS-1. I also have that same service manual but I'd forgotten about the cap mod or shielding cuz, it's been decades since I had need to read it again.

Those wooden cabinets were quite popular for a while & I guess it was to add a touch of class to a product. Not good for shielding obviously. And no one used torroidal transformers back then that could reduce hum/noise.
 
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