[sdiy] Power supply for Big Briar Etherwave Theremin

[Phil Macphail]

Also look at the schematic, and notice that the ground pin on the PSU connector is connected to one of the AC supply pins. Connecting the CT of a transformer to the GND pin will result in one side of the secondary being shorted.


Phil.

> On 6. Jul 2022, at 09:05, Peter Pearson via Synth-diy <synth-diy at synth-diy.org> wrote:
> 
> https://manuals.fdiskc.com/flat/BigBriar%20Etherwave%20Service%20Manual.pdf <https://manuals.fdiskc.com/flat/BigBriar%20Etherwave%20Service%20Manual.pdf>
> Read page 8 of the service manual where it says - and I'm quoting here - "WHY IS THE POWER ADAPTER GROUNDED?"
> 
> On Tue, Jul 5, 2022 at 7:04 AM Gordonjcp <gordonjcp at gjcp.net <mailto:gordonjcp at gjcp.net>> wrote:
> On Thu, Jun 30, 2022 at 02:41:07PM -0400, Peter Pearson via Synth-diy wrote:
> > https://manuals.fdiskc.com/flat/BigBriar%20Etherwave%20Service%20Manual.pdf <https://manuals.fdiskc.com/flat/BigBriar%20Etherwave%20Service%20Manual.pdf>
> > 
> > The schematic is here.  A DC supply won't work.  The theremin might be
> > fussy about grounding though, so you'll definitely want a center-tap on
> > your power adapter.  I wouldn't recommend trying to cheat a barrel jack AC
> > power adapter in there.
> 
> If you look at the power input circuit, there are only two connections.  There's nowhere for a centre-tap to go.
> 
> It's a simple transformer fed into a pair of half-wave rectifiers, same as the various crappy modular PSUs that are kicking around.
> 
> Everyone is making this waaaaaaaaaaaaaaaaaaaaaaaaaaaaaay more complicated than it needs to be.
> 
> A 15V transformer will be fine.  It doesn't need a centre tap.  Anything over 200mA will be fine.
> 
> -- 
> Gordonjcp
> 
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