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9. Servicing
f o r c e
VACUUM TUBES
The FORCE microphone preamplifier utilizes one 12AX7 per channel. Equivalent tube types are 12AX7WA,
ECC83, 7025, CV4004. The lifespan of these tubes is in the order of 5000-6000 hours, after which time the tubes
should be replaced. If the FORCE has become noisy, this could be related to tube wear. Consult your dealer or
purchase new tubes from Manley Labs. We suggest low noise and graded quality. Simply hold the tube firmly at
its base and vertically pull upwards, freeing the tube from its socket. When inserting a new tube ensure all the
pins are straight and align with the receptacles of the tube base before pressing down firmly to locate the tube
correctly.
GAIN SETTING JUMPERS
The FORCE is shipped factory set for 50dB of gain for the HI gain setting. (Diagam 2-switch (2)) If required the
unit can deliver a further 10dB of gain so the overall gain of the preamplifier would be increased to 60dB, which
may be required for some users. Each channel is equipped with a jumper to select the desired gain. The jumper
is red and is located to the right of each tube. Please refer to diagram 4, for their locations. With the red
jumper in the top position 50dB of gain is selected and with the jumper in the lower position 60dB of gain is
selected.
GROUND LIFT JUMPER
If necessary the Circuit Ground can be disconnected from the Chassis Ground. This practice is usually required if
hum-loops cannot be cured in any other way. Removing the jumper at P4 will break the ground.
PEAK METER CALIBRATION
These trim pots are initially set at the factory for the LED Peak Level meter and should not require any
additional adjustment by the user, as the solid-state circuitry does not drift over time.
PSU FUSE
The PSU fuse is a safety fuse rated at 2A (T) 250V AC. If this fuse fails the switched-mode PSU has suffered a
catastrophic failure and it is unlikely that it can be repaired. The unit will have to be returned for service.
12AX7 12AX7
PEAK METER CALIBRATION TRIM
Please ensure the unit is unplugged and switched off before attempting any of the procedures below.
11
GAIN SETTING JUMPERS
12AX7
12AX7
Diagram 4
GND LIFT JUMPER
PSU FUSE
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