[sdiy] Need help reading a schematic

Rutger Vlek rutgervlek at gmail.com
Thu Aug 13 14:28:29 CEST 2020


If you can figure out the required current on the +/-15V and +5V rails you
might also consider replacing the whole PSU system with an off-the-shelf
switch mode PSU (e.g. meanwell has these multi-voltage units). In that case
you'd bypass even the regulators currently fitted to the unit. I've had my
share of linear PSU repairs as well, and often prefer it to keep things
original, but I've been surprised more than once about the difficulty to
find the right transformer. Also bear in mind that small deviations of the
transformer (from the original) may have consequences for the heat
generated by the regulators. The dissipation measures originally taken by
the designer may suddenly not be enough, when you supply a slightly larger
input voltage (because the transformer was rated for the same AC voltage as
the original, but at a slightly higher load).

Rutger

Op do 13 aug. 2020 om 09:46 schreef Jean Bender <lofideadbeat at gmail.com>:

> Hi ! Thanks for your answers. Well i got this schematic from dynacord,
> but they didn't send more, especially the power part schematic. This
> schematic is part of the owner manual, but 6 sheets are missing ! I
> gonna have a look to this site selling service manuals, but i'm not
> sure i wanna pay for that, i'll see.
>
> As 2 fuses always blow up if powered, i'm pretty sure the power
> transformer is dead, it's not a thoroidal one. I gonna try to get a
> 220V to 2 secondary 18V AC and see if it lett the pdd14 can go back to
> life ;).
> The regulators are LM7815, 7915 and 7805.
> The only thing i don't get yet is that two wires go from one
> secondary, the V+ one goes through a fuse and then directly to the
> pedal board jack. I guess i don't need it actually, as i don't have
> the pedalboard !
>
> Thanks for your answers !
> Best
>
> Le jeu. 13 août 2020 à 00:47, KA4HJH <ka4hjh at gmail.com> a écrit :
> >
> >
> > On Aug 12, 2020, at 2:47 PM, John Speth via Synth-diy <
> synth-diy at synth-diy.org> wrote:
> >
> > And lastly, for actual repair, the hardest part will be finding a
> transformer that fits in the housing.
> >
> >
> > Especially if it's toroidal. I'm guessing +/-18V RMS.
> >
> >
> > Terry Bowman, KA4HJH
> > "The Mac Doctor"
> >
> > https://www.astarcloseup.com/
> >
> > “The book said something astonishing, a very big thought.
> > It said that the stars were suns, only very far away.
> > The Sun was a star, but close up.”—Carl Sagan, Cosmos, 1980
> >
> >
> > _______________________________________________
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>
>
>
> --
> Jean Bender
>
> Hak Lofi Record
>
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