Vectronics VEC-841K - Manual (Page 18)

VEC-841K Owner's Manual Tunable SSB/CW Audio Filter Kit
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! ! 1. Locate resistor R26. This is a 500K linear dual potentiometer with six
(6) legs. This part will be marked "105-2011" on the backside of the
part.
! ! 2. Insert R26 into its mounting holes until it stops, making sure that all
six (6) legs are inserted into the board. Also, make sure that the shaft
is parallel with the circuit board surface. Solder in place.
! ! 3. Locate resistor R27. This is also a 500K linear dual potentiometer.
Insert at R27, making sure that all six legs are inserted and the shaft is
parallel with the circuit board surface. Solder in place.
At this point, your kit is finished and it's time to take a well-earned break! When
you come back, be sure to give your work a close "quality control" inspection.
PC Board Inspection:
Before applying power to your kit, give it a thorough QC (quality control)
inspection. This will help you find inadvertent assembly errors that might
prevent the filter from working or cause damage to sensitive parts. Follow this
procedure:
! Compare parts locations against the parts-placement diagram. Was each
part installed where it is supposed to be? Was the correct value used? Start
at one side of the board and work your way across in an organized pattern.
! Inspect the solder side of the board for cold-solder joints and solder bridges
between tracks or pads. Use a magnifying glass to obtain a clear view of the
track area. If you suspect a solder bridge, hold the board in front of a bright
light for a better view. All joints should be smooth and shiny, indicating
good solder wetting and flow. Resolder any beaded or dull-appearing
connections.
If you find a construction error and need to remove a part or two, it will be easier
if you have the right tools. One very convenient item for freeing soldered-in
parts is a "solder sucker". This consists of a suction bulb or a spring loaded
vacuum pump that draws molten solder away from the pad and lead.
Alternatively, you may use a special copper braid called "solder wick" (solder
suckers and solder wick are both available at your local Radio Shack or
electronics supply house). If you suspect you've damaged a component during
removal, better to replace it than risk reusing it!
Finally, rosin flux can absorb moisture, which may cause a problem for some
electronic equipment. To remove flux, use isopropyl alcohol (or 95% grain
alcohol) and an old toothbrush. Apply a generous amount of alcohol with the
toothbrush and scrub gently. Once the flux has fully dissolved, blot the bottom