NS69 schematic?

[skeptic12]

I have looked in the tech docs section here and all over the interweb but can't find schematic for NS69 psu.

I found one in my box of wayward units and want to test it. The board is marked 117V and I don't see a way to convert to 230v

Anyone have a copy?
Thanks!

 

[Khron]

Photos of the inside of the unit might help even without schematics. Hopefully good odds the transformer is a dual-primary one, with the windings parallelled for 117V operation - those would need to je connected in series for 230V operation.

https://talema.com/wp-content/uploads/products/schematic-drawing-dual-primary-series-parallel.png

 

[skeptic12]

thanks for chiming in! here are some photos.

 

[Khron]

What about the underside of the circuit board?

 

[skeptic12]

so it looks like taps- trace cut to the 367 ohm tap and fuse connected to the 764 ohm tap which corresponds to what I see at switch and where the mains cable is connected, so I am assuming I am ok for 230VAC? plus mains cable has red and black wire, likely UK?

now all I need is a stereo mic!

 

[Khron]

One transformer leg does not and can not have a resistance, on its own. Resistance is measured between TWO points in a circuit.

Maybe if you try to more clearly point out between which solder pads you measured those resistances? Also, consider using yellow or white for the annotations - red is pretty difficult to distinguish against the circuit board colour.

 

[skeptic12]

sorry, how's this? I guess the fuse holders were designed for changing the voltage- no reason cut the trace or have the two fuses installed

 

[RuudNL]

The NS69 is 100-130 or 200-240 volt.
https://www.radiomuseum.org/r/neumann_netzgeraet_ns69.htmlAs far as I see (two fuse holders) it is a matter of lifting the fuse connected to the 367 ohms tab and placing a fuse connected to the 764 ohms tab. No need to cut traces!
The 764 ohms is probably the 'end' of the winding, the 367 ohms is the 'hafway' connection (100-130 V)

 

[skeptic12]

thanks for that link and info!
strange that someone cut the trace but maybe they couldn't find a schematic either