Yamaha CA-400 asymmetrical power rails?

[Artie]

I've never seen this before, and was wondering why they might do this? The positive rail is fairly conventional, feeding both the positive output and driver. But the negative rail provides a different voltage for the driver than the output trans. Can anyone tell me why they might do this? Just seems odd.

Here's a simplified drawing of the relevant PS circuit, and then the full schematic if anyone wants to see it.

Thanks all;
Artie

Edit: Whats especially odd, is that it requires a special transformer, (not cheap), that provides an extra "tap".

And here's a link to the full schematic if you want to see it: Yamaha CA-400 (It's fairly large.)

 

[Artie]

No one?

I know it's a somewhat obtuse question, but it intrigues me. Yamaha had to use a unique transformer to obtain the oddball negative voltage. It just seems like an odd thing to do on a low-line amp. They don't do it on any others. (That I've seen.)

 

[pezza89]

does anyone know the value of the zenar diode on the output board? i need a replacement but not sure of its value! thanks!