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- Cosmic Ampworks
(Wire to tonestack)
The tail resistor R28 of the phase inverter is replaced by mounting the included 10k resistor diagonally to the circuit board, with
Figure 25
one leg in the rear hole of (the removed) R28 and the other leg in the front hole of R8. Presence wire are soldered to the front hole of R28
(ground) and the rear hole of (removed) wire bridge J12. Also visible is a wire that runs to the new tonestack – to be discussed further
down.
Wire from rear
hole of J12 (Figure
11) to left lug of 5k
pot
Figure 26. Connect the presence and negative feedback (NFB) controls: solder the wire that runs from the rear hole of J12 to the left lug of
the 5k potmeter. Solder the other strand to the right lug. Solder the legs of the 0.1uF capacitor to the right and center (wiper) lugs of the 5k
potmeter. Solder one leg of the 120k resistor to the left lug of the 5k potmeter and the other leg to the left lug of negative feedback control
(1M potmeter, B = linear taper). Keep the legs long enough, so they can bridge the distance between the two pots when they are mounted
in the holes where the Send/Return/Lineout jacks used to be. The run a wire from the center tap of the 1M potmeter to P3 (Figure 27), on the
left rear of the board.
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www.cosmicampworks.com
- The Ultimate Harley Benton GA15 Mod Kit- Version 1.4 - 200127
®
To presence
control – front
hole of R28
10k(*)
0.1uF
120k
5k (presence)
22
To presence
control – rear
hole of J12
Wire from front
hole of R28 (Figure
11) to right lug of
5k pot
NFB wire from
output transformer
(P3)
1M (NFB)
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