Discussion about the Korg PolySix synthesizer

hello,

it's been awhile since my circuits courses in school - can anybody
tell me exactly what purpose is served by removing c40 and replacing
r91 with a diode?

thanks!

Brian,

The old battery was a nickel cadmium type and was rechargeable. The 
replacement which you are trying to fit is undoubtedly a lithium coin 
cell which should not be charged. The new diode (in place of R91) is 
to prevent the 5v supply reaching the cell whilst the circuit is 
powered on (the diode is reverse biased). When the supply is removed 
the current can flow from out of the battery and keep the SRAM 
running (the diode is forward biased). This diode goes in the place 
of R91. C40 is removed because it is part of a decoupling arrangement 
which is now no longer relevant with R91 removed. I don't see any 
problem leaving it in circuit if you really must!

Cheers,
Andy


--- In PolySix@yahoogroups.com, "Brian Down" <mathletics@...> wrote:

>
> hello,
> 
> it's been awhile since my circuits courses in school - can anybody
> tell me exactly what purpose is served by removing c40 and replacing
> r91 with a diode?
> 
> thanks!
>