User manual

Vetta and FBX Service Hints Page 1 of 2
Engineering
Vetta and FBX Service Hints
If the PS_VALID line is inadvertently short-circuited, D15 on the power supply will
almost certainly fail. This will keep the audio from appearing on the Direct Outputs, and
possibly on the speaker outputs.
If the main FETs (Q3 & Q15) on the power supply are shorted, a series of components
will most likely fail. Replace R21, R7, R55, R49, R12, R11, R15, D4, Q3, Q15, Q11, Q2,
and U2.
If unit locks up intermittently and or settings aren’t remembered after power cycle, check
SRAM battery to ensure voltage isn’t significantly below 3V. Replace the battery if it is
below 2.7V and check the SRAM current consumption by measuring less than 100mV
across R185.
If 7 segment numeric display behaves erratically, check to ensure proper insulation
between pins and chassis on header connecting numeric display PCB to U.I. PCB.
If displays show garbled information or none at all, check to ensure proper seating of
ribbon cable from main board to U.I. board. Note: obvious but common.
Be extremely cautious when removing knobs for the three global controls. The shafts on
these pots will pull out easily. The suggested method is to hold the shaft of the pot from
the inside of the chassis with pliers while pulling the knob off. If the shaft breaks, the pot
CAN be replaced without removing the entire U.I. board. The method is to first cut the
pins of the pot, remove it and then de-solder and remove the pins remaining in the board.
If the power supply must be removed from the unit, it is not necessary to remove the
speaker output PCB. There is a hole in this board, which allows for accessing the power
amp screw below. A magnetic screwdriver is handy to put the screw back in.
Be very careful while working on the power supply PCB. The PCB section between the
AC receptacle and the transformer has high voltages.
Notice that the power connectors have a lever, which must be pressed to unplug them.
Also while pulling or pushing on these connector, try to support the PCB with the other
hand to avoid excessive stress.
Both power connectors on the speaker output board are 4 pin wide. The PCB screening
shows which one plug where.