Vectronics VEC-1680K - Manual (Page 17)

VEC-1680K Owner’s Manual Vacuum Tube Preamp
17
Before installing the control knobs, set turn potentiometer shafts fully
counterclockwise.
! ! Find a knob and install it on one of the potentiometers. Set the knob
pointer to the 7-o'clock position and tighten the set screw.
! ! Repeat knob installation for the second potentiometer.
Locate the bottom cover for the chassis plus the six (6) self-tapping screws.
! ! Install the bottom chassis cover and secure.
! ! Find the sheet with four (4) rubber stick-on feet attached. Install a rubber
foot at each corner of the bottom panel.
This concludes assembly of your VEC-1680K preamp kit.
High Voltage Warning: Your preamp's 12AX7 tube operates at potentially
lethal voltages. Please read the Testing and Alignment section of this
manual carefully before applying power or attempting to operate your
preamp!
TESTING AND ALIGNMENT
The VEC-1680K preamp has no internal adjustments and should work as
specified without additional set-up. However, there's always the remote
possibility that a construction error or defective component could prevent proper
operation. Before attempting to use your preamp, follow this initial test
procedure:
1. Turn both controls (Gain and Output) fully counter-clockwise.
2. Make sure the Power switch is Off.
Note: Do not plug in an instrument or amplifier at this stage of the test.
3. Locate the 12-VAC wall adapter and plug its cord into the 2.1mm power
jack.
4. Plug the wall adapter into a 110 VAC mains.
5. Turn the Power switch On. The tube's filament should light.
If the filament fails to light, turn the preamp Off at once. First, check the 12AX7
filament for continuity. Remove the tube and hold it with pins facing you. The
first pin clockwise of the gap is pin 1. Count to pins 4 and 5, and check
resistance with an ohm meter. If the filament is good, you'll see a short. Pin 9 is
the filament's center tap.