AW: [sdiy] power supply (un)symmetry

[Matthias Herrmann]

okay john,
79xx/78xx regulators don't seem to be the best choice!?

-----Ursprüngliche Nachricht-----
Von: owner-synth-diy at dropmix.xs4all.nl
[mailto:owner-synth-diy at dropmix.xs4all.nl]Im Auftrag von John Luciani
Gesendet: Donnerstag, 1. Juni 2006 22:18
An: Matthias Herrmann
Cc: Synth-Diy
Betreff: Re: [sdiy] power supply (un)symmetry


On 6/1/06, Matthias Herrmann <matthias.herrmann at fonik.de> wrote:

> i recently built a little powersupply for the soundlab i am building. it
> converts 9VAC to +9V/-9V DC and +12V/-12V CD (for the midi2cv converter).
> its made out of four diodes, 4 polarized caps and some 78xx/79xx. actually
> it is a mod of the doepfer A-100 miniNT bus.
> unfortunately it is not 100% symmetric. actually it provides +9,2V/-8,8V
> (+12V/-12V accordingly unsymmetric). i don't know whats wrong yet.
>
> i wonder if this would be critical?
> and if so, how to fix it with few parts?

It almost seems like there is problem in your power output ground since one
supply is high by the same amount that the other is low. You may want to
check
for grounding problems.

A 2.5% error is probably within the output voltage specification of
the regulators
(check the Vo parameter in the datasheet). If you need higher accuracy
you probably
need a different design.

(* jcl *)

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