Using The Amp Without Protection Circuit; Removing The Protection Circuit Board; Repositioning The Protection Circuit Board - SPHINX Project Twelve Service Manual

SPHINX
7. USING THE AMP WITHOUT
PROTECTION CIRCUIT
To adjust the internal controls of the Project Twelve
the protection circuit board may be removed.
This ensures that all adjustment points on the main
board are freely visible and accessible (instead of
through small openings in the protection circuit
board).
WARNING!
The amplifier may be used without the protection
circuit.
We do not recommend this however while this
prevents the output from being disconnected in
case of any malfunction.
SPHINX is not responsible for any damage
caused by the removal of the protection
circuit or the use of the amp without the
protection circuit!

Removing the protection circuit board

The protection circuit board is mounted on top of
the upper main printed circuit board of the amplifier.
The drawing "Schematic layout of project 12 with
securityprint" (page 14) shows the main board of
the Project Twelve with the protection circuit
including all the parts mentioned below. Use the
following steps:
1. Remove the top cover plate of the amp. It is
fixed with one hex screw (M4x12) at the rear
panel
2. Remove the two small screws (M3x6) of the
protection circuit board.
3. Unsolder the five wires at the top-left corner
(Audio-IN).
4. Unsolder the two PTC-resistors (for the over-
temperature protection at 70 °C).
5. Carefully remove the circuit board (there is only
one way of doing this due to the mounted
Balanced/Unbalanced switch):
a) Lift up the front side of the board so the large
connector is disconnected from the main circuit
board.
b) Lift the rear side of the board to disconnect
the other connector.
Now you may remove the board.
6. Connect the input signal to the main circuit
board with the special Servicing Cable (*).
7. Reposition the jumper from JP2 & JP3 to JP1 &
JP2.
The output relay now works without control
signal from the protection circuit.
Project Twelve Service Manual

Repositioning the protection circuit board

To reposition the protection circuit board you use
the steps from the previous "Removing the..."-
procedure but in reverse order.
1. Reposition the jumper from JP1 & JP2 to JP2 &
JP3.
If not, the protection circuit will not be able to
disconnect the amplifier's output.
2. Position the board over the mounting positions
and stick the Balanced/Unbalanced button
through the appropriate opening in the rear
panel of the housing.
3. Carefully insert the rear connector into the
corresponding main circuit board socket and
then the front connector in it's socket.
Attention:
Incorrectly positioned connectors may cause
damage to the Project Twelve and the pre-amp.
4. Fix the protection circuit board position with the
two small screws.
5. Solder the five wires to their correct positions
(position #1 is the one at the rear, see also the
drawing):
1) Red (+) wire from BALANCED IN
2) Red (+) wire from UNBALANCED IN
3) Black wire (ground) from BALANCED IN
4) Black wire (ground) from UNBALANCED IN
5) Blue (-) wire from BALANCED IN.
6. Solder the two PTC-resistors to the circuit
board.
7. Replace the top cover plate of the housing and
fix it with the hex screw.
(*) If there is no Servicing Cable available you may
make one yourself using a suitable connector.
Connect the wires as follows:
•
Pin 1 (and 2) = negative signal: connect to blue
wire from Balanced In
•
Pin 3 (and 4) = ground: connect to black wire of
both inputs
•
Pin 5 (and 6) = positive signal: connect to red
wire of both inputs
The 6 pin connector at the main board then can be
used as the signal input.
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