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- Cosmic Ampworks
For attaching the potmeters of the new tonestack, gain and volume controls to the chassis as indicated in this
manual, some extra holes need to be drilled in the chassis; Figure above)
6. Wire a DC power supply for the preamp heater filaments.
a. Carefully de-solder and remove the L7912
18). Make sure to only briefly heat the legs, as the L7912 is a heat-sensitive part (!) If possible,
clamp the included crocodile clip to the leg that you are de-soldering, as a makeshift mini-
heatsink.
b. Drill 4 small holes in the heatsink (Figure 19), large enough to accommodate a tie wrap.
c. Drill 5 holes in the chassis (Figure 20): a larger one for the three wires running to the voltage
regulator and four smaller ones, for attaching the heatsink with tie wraps (Figures 19, 20). Copy
the layout of the four smaller holes from the four holes in the heatsink (see 6 b), with a marker or
pencil. Then drill. The distance between hole 1 and the center of the imaginary line that connects
holes 2 and 5 should be about 1.5 cm (Figure 20). After drilling, smoothen the edges of hole 1 with
some sanding paper and/or a file and remove any burrs.
d. Clip three lengths of speaker wire, of some 7 cm each. Separate the strands of one of them (so you
have one single stranded and one double stranded wire). Solder one strand to each of the voltage
regulator's legs. Make sure the legs don't touch each other or even come close – careful soldering
and minimal quantities of soldering wire required! It is probably easiest to lay the wires parallel to
the component legs for soldering. NOTE: if you clip the wires too short, it may be difficult to get
underneath the circuit board later on! Again, make sure to only briefly heat the legs, in order not to
damage the component. For that reason, if possible, it would perhaps be better to
L7912 to the heatsink (with some thermal grease put on the contact surfaces),
3
NOTE: if things should fail with the L7912 and the component gets damaged, please note that it is then still possible to
use the remaining voltage regulator, the L7812, instead of the L7912. It supplies -12 V DC, it supplies +12 V DC. See
point 6.j.ii.
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www.cosmicampworks.com
- The Ultimate Harley Benton GA15 Mod Kit- Version 1.4 - 200127
®
Drill some new holes in
chassis for attaching the
new potmeters (upside
down) as indicated in the
manual (the original ones
were attached to the circuit
board).
negative (12V) voltage controller from the board (Figure
3
16
Dedicated to the Advancement of Stellar Tone!
first
mount the
then solder
.
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