Au-555 vr901?

[mikstick]

alignment for the au-555 is made via vr801 to vr804, with the help of a dummy load and an occilloscope:worried:

This amp has lead me on the path to getting a bit of a bench together, taking alot of time, and steep learning curve as ever.

Anyway, curiousity, whats with vr901? anyone familiar? Am I being lazy

pics inc
oh amp888 has a load of pics of the boards of the au-555
http://amp8.com/sansui/au555-20000/au555-2.htm

 

[skippy124]

Hi
As far as I can remember, VR901 is the adjustment for the basic protection circuit in the AU-555....

Cheers

John

 

[mikstick]

I havent seen any description or any info on how or when or what you would adjust to with this vr901, any other info would be gratefully accepted

mike

 

[skippy124]

Hi Mike,

I reckon that this is "factory adjustment" - i.e. done once at the final test and not required to to be re-adjusted in the field.

The circuit works by "monitoring" the voltage across the output emitter resistors (R839, R840) that are on the low side of both channels via D903 and D904. If the voltage rises to level that could damage the amp (preset via the POT VR901), then the SCR fires, and pulls down the high side driver transistors TR805 an TR806 via D901 and D902.

Hope that helps

Cheers

John

 

[mikstick]

that's great, I really appreciate your time explaining that for me,
:tresbon:

mike