Fix errors 407.1, 407.2, 407.3 - Front end 2V/200V/750V
407.1 - Cannot measure 7V ±0.15V at A/D IN.
407.2 - Cannot measure 0.7V ±0.2V at A/D IN.
407.3 - Cannot measure 0.14V ±0.04V at A/D IN.
VRIN is buffered by U517 and tied to BUFF. The signal at BUFF is routed through R233
to pin 1 of NET1 (R557). The voltage at pin 4 of NET1 is routed through U526 (DCF
pulled low) and Q516, and applied to the input buffer (Q512 and U520). The buffered
signal is tied to AMP IN.
The signal at AMP IN is then routed to the variable gain ampliÞer (VGA) and, being
positive, follows the non-inverting x10 path that consists of R530, Q508, Q507, U519,
R531, U509, Q501, and U516 to pin 12 of multiplexer U511.
The output (OUT) of the multiplexer is routed through buffer U342 to ACV/A. The signal
at ACV/A is routed through U320 (/AC pulled low) and applied to the A/D buffer
(U322), which is conÞgured for x1 gain.