[sdiy] +7 and + 2 volt supply

[Adrian Corston]

The power circuit in the RSD-10 provides 0V (ground symbol), +2V,
+4.5V, +7V and +9V.  +2V/+7V (a 5V difference) are used for Vss/Vcc
on "digital" chips (e.g. IC12 - 4040 counter, IC16 - 4164 DRAM) and
0V/+4.5V/+9V are used for Vee/GND/Vdd on "analogue" chips e.g. (IC2 -
uPC1571C expander) for a bipolar supply.  For example, see IC1a which
is a unity gain inverting op-amp with the + terminal at +4.5V as a
virtual ground.

Cheers,A.

----- Original Message -----
From: "Adam Inglis" <21pointy at tpg.com.au>
To:"Synth DIY" <synth-diy at synth-diy.org>
Cc:
Sent:Mon, 10 Jun 2019 12:10:24 +1000
Subject:[sdiy] +7 and + 2 volt supply

 In another thread I mention a bunch of Roland/Boss delay boxes I’m
looking at.
 Most of these take the usual Boss 9 volt supply and regulate it with
a 78L05 giving a +5 to zero volt supply.
 However, in one of these machines, which uses much the same circuitry
as the others (the RSD-10) and the same 9 volt DC adapter, Roland have
used a 78L07 next to a 79L05 to give a +7 v to +2 v supply.

 Anyone care to hazard a guess as to why?
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