NAD 7225PE schematic question re: polarity

[doolybird]

Hi All,

I have a NAD7225PE and have decided to undertake a recap. I have noticed C601 and D602 are missing from the amp and a wire is connected from the negative side of C601 to the base of R14. refer attached. My question is does this look correct on the schematic ? Is the polarity as marked on the schematic incorrect ? i.e. positive to gound ?

Any comments appreciated. I started to put a capacitor and diode where they are missing but I am not too sure I should, at least as the polarity is shown anyway.

Richard

 

[mbz]

D602 cathode connects to -50Vdc input to regulated power supply.
What does D602 do? 0.6Vdc voltage drop. What does C601 (22uf/100V)
do? Smoothing? C517 (330uf/63V) performs the same task. Probably
some NAD cost cutting measures?

C601 polarity is correct, +ve to GND. Better to think of cap
terminals as "more positive and more negative". D602 anode/C601 -ve
is about -50Vdc so GND is at a higher (more positive) voltage.

 

[JonSnell Electronic]

D602 used to pull R601 & C601 to negative junction of C519 & R514.
In the early days a common issue was hum at start up, caused by C519 going dry.
Removal of this diode and capacitor stopped the issue.
If you mean it is now routed to R514 then this is correct on later production chassis.

 

[doolybird]

Thanks for the replies, much appreciated. If it were you would you leave them out ? I guess so given the NAD designers ledt them out of future amplifiers.