Yamaha CS80

rj krohn wrote:
> hi folks, sorry this is only peripherally 80-related. i have stumbled into 2 cs-40m's for dirt cheap, both non-working. my question is this: is this a power supply that needs to see a load when powered up, or would i need to short any of the voltages or ground, or something of that sort to power up with no load? after doing some testing, im led to believe that something beyond the PSU is causing the main fuse to blow.
 From what I can see on the link you sent, the supply should be fine on 
its own. To clarify, the CS80/60/50 PS doesn't need a load for 
stability. It's switching supplies, like in PCs, that need a load or 
they go bye-bye. The CS80/60/50 PS does need connections between the 
voltages outputs and the sense inputs. Sensing is used to measure the 
voltage at the load, compensating for any drop across the big and long 
power supply wires to the PC boards.

If you look in the lower right corner of the big, foldout CS80 
schematic, you'll see that the +15 and -15 volt outputs have sense 
inputs. If you ever wanted to run this supply disconnected from the rest 
of the guts, you need to connect +15 to +15S and -15 to -15S. Note that 
they only do this on the analog supplies that affect tuning.

It looks like the CS40 is small enough, with a much smaller current 
draw, so they weren't worried about voltage drop and used a more common 
internal sensing/feedback on the +15 and -15 volt outputs.

>  here's a link to the overall circuit diagram:
>
> http://www.megaupload.com/?d=FP73F7MD
>   
Thanks for the CS40 schematic!  I'll put it up on my CS80 site when I 
get a chance.

 David