Bug #277

K2 - ERROR 405.2 โ€“ Absolute value x10 gain comparison; large +DAC output

Added by tin about 7 years ago. Updated over 4 years ago.

Status:ClosedStart date:19/07/2012
Priority:NormalDue date:
Assignee:tin% Done:

0%

Category:-
Target version:Keithley 2001 #2

Description

Voltage at A/D IN not the same as test 405.1.

DAC U531 is programmed to generate 0.51 VDC at PRECOMP. That signal is then applied to ACF through R560 and U532 (DAC line pulled low). ACF is routed to AMP IN via U526, Q516, and the AC input buffer.

AMP IN is tied to the inverting and non-inverting paths of the variable gain amplifier (VGA). NETOUT (output of U519) is routed to the Zero-Crossing Amplifier which, based on the polarity, generates the appropriate COMP- signal that is applied to com- parator U507. The comparator selects the path that the AMP IN signal will follow through the VGA by closing the appropriate analog switches of U509.

The positive (non-inverting) AMP IN signal path with the VGA at x10 is through R530, Q508, Q507, U519, R531, U509, Q501, and U516 to pin 12 of multiplexer U511. The out- put (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 configured for x1 gain.
Measure the voltage at A/D IN. It should be same value that was measured in test 405.1.

Suspected components

U342
U320
U322
U519
U507
U509
U526
U532
R560
Q516
U531
R530
Q508
Q507
R531
Q501

History

#1 Updated by tin about 7 years ago

Test 405.8

Q310, Q305 and R591.

#2 Updated by tin over 4 years ago

  • Status changed from New to Resolved

#3 Updated by tin over 4 years ago

  • Status changed from Resolved to Closed

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