Channel 2 Vertical Preamplifier

The Channel 2 Vertical Preamplifier functions the same as the Channel 1 Vertical Preamplifier previously described.

with the exception of an additional pair of transistors that performs the inverting function. In the Normal mode of operation, Q257 and Q267 are biased on and Q258 and Q268 biased off by INVERT switch S264 grounding one end of R263. In the Invert mode (INVERT switch pressed in), cross-wired transistors Q258 and Q268 are biased on and Q257 and Q267 biased off by grounding the junction of R256 and R266. Invert Bal potentiometer R264 is adjusted to correct for dc offsets between the two switching-transistor pairs. When R264 is correctly adjusted, a baseline trace will maintain the same vertical position as the amplifier is switched between Invert and Normal.

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