Voltage for Studiomaster 16-4-2

[Sune T. B. Nielsen]

Hi
I got an old mixing board called Studiomaster 16-4-2. Using google it seems
to me that there are different ones called that and this is the one with
five band EQ and LED meters.

I didnt get a wire for supplying power to it so i tried adding a standard
power jack.

But then the fuses in my appartment blew.

On the outside of the cabinet is written:

"Fuse T2A (Inside voltage selector) 50/60 Hz ~ 100 120 220 240 V, 50VA Max"

But inside there is no fuse and no voltage selector. The wires from the
voltage input goes to the power on/off switch and from there directly to the
transformer coil. From the coil four wires goes to the phantom power switch
and six to some circuit that then gives power to the rest of the board.

My first thought was that a previous owner could have added his own power
supply, but then i noted that all the capacitors are by same brand (and
looks like they are of same age) as the rest in the board.

I found a drawing of the power supplies of a Studiomaster 16-4-2 here
http://fa.utfs.org/diy/
It has a T2 fuse and says that you should the connect in series for 240 V
power or in parallel for 120V.

Could it be that the board is connected for 110 V while im giving it 220?
Which wires are to be connected in series if want to change which power it
can use?

Any help or ideas is much appeciated

Best whishes

Sune T. B. Nielsen, Denmark

 

[TimPerry]

Hi
I got an old mixing board called Studiomaster 16-4-2. Using google it seems
to me that there are different ones called that and this is the one with
five band EQ and LED meters.

I didnt get a wire for supplying power to it so i tried adding a standard
power jack.

But then the fuses in my appartment blew.

On the outside of the cabinet is written:

"Fuse T2A (Inside voltage selector) 50/60 Hz ~ 100 120 220 240 V, 50VA Max"

But inside there is no fuse and no voltage selector. The wires from the
voltage input goes to the power on/off switch and from there directly to the
transformer coil. From the coil four wires goes to the phantom power switch
and six to some circuit that then gives power to the rest of the board.

My first thought was that a previous owner could have added his own power
supply, but then i noted that all the capacitors are by same brand (and
looks like they are of same age) as the rest in the board.

I found a drawing of the power supplies of a Studiomaster 16-4-2 here
http://fa.utfs.org/diy/
It has a T2 fuse and says that you should the connect in series for 240 V
power or in parallel for 120V.

Could it be that the board is connected for 110 V while im giving it 220?
Which wires are to be connected in series if want to change which power it
can use?

Any help or ideas is much appeciated

Best whishes

Sune T. B. Nielsen, Denmark

from the schematic you can tell that the transformer primary can be wires
either for 110 or 220.

if wired for 110 and 220 is applied any or all parts of the power supply may
be damaged. damage may extend beyond the power supply (hopefully the 7815
regulators would short first and therefore protect the following circuitry)

if you are lucky only the bridge rectifier will be shorted.

take this unit to a competent service technician.

have the tech wire for your desired voltage, repair the unit making sure the
proper size fuse is installed. normally a fuse for 220 vac operation is 1/2
the value of the fuse for 110 vac operation.

 

[Sune T. B. Nielsen]

Have a look here: http://www.nonono.dk/knox/mixer/