Fluke PM3082 Service Manual page 489

8 - 2 2
Autocalibration of horizontal gain and offset
As input signals are used signals generated by generator circuit (D7004, N7014, N7015) on the DTB
circuit diagram (unit A1). The accurate output signals are MCLOOP (MTB) and DCLOOP (DTB).
The output signals are measured on the X-deflection plates of the CRT. This results in the signal
XCAL (horizontal plates).
Error Calibration step
code
013
X-pos, MTB x10
015 X-pos, MTB x1
01B X-pos 0 div, timebase
01C
X-pos -3 div, timebase
014 X-gain, MTB x10
016 X-gain, MTB x1
017 X-pos, DTB x1
019
X-pos, DTB x1
018
X-gain, DTB x10
01A X-gain, DTB x1
01D X-pos 0 div, X-defl
01E
X-pos -3 div, X-defl
Autocalibration of offset delay line driver and channels 4, 3, 2 and 1
As input is used the accurate signal ATCAL generated by circuit with D1152, N1104 on the circuit
diagram of the input attenuators (unit A1).
The output signals are measured on the Y-deflection plates of the CRT (YCAL).
Delay line driver offset
The delay line driver input signals FNC..OUTO and FNC..OUT1 are differentially 0 V. D.A.C. output
DLDOFFSET is adjusted such that YCAL detects the mid screen position.
Error Calibration step
code
02C Delay line
driver offset
Offset trace
02E
02F separation 0 div
idem, 3 div
Position midscreen
ATCAL is set such that a positive trace shift is obtained. The microprocessor controls the trace back
to just above midscreen via POS4 in the Y-functions section.
DC loopgain
ATCAL generates a 13 Hz sq-wave. The microprocessor monitors the top of the sq-wave (via YCAL)
at successive moments in time. In successive steps AT4LFCAL is adjusted for a correct sq-wave
response.
CORRECTIVE MAINTENANCE PROCEDURES
Input Control signal
MCLOOP TBXPOS
(A1/17A/7075) (A1/17/R7099)
. .
XTRAGC
J
MCLOOP
(A2/3/N2002)
\ DCLOOP
TBXPOS
J
(A1/17/V7075)
J- DCLOOP
XTRAGC
1 LEVDTB
TBXPOS
J
(A1/14/R7681)
Control signal
Input(s)
FNC..OUT0 DLDOFFSET
(A1/9/R5018)
FNC..OUT1
(A1/9/R1313.R1314)
TRASEP
[ ATCAL
(A1/9/R5021)
J
(A1/1/R1008)
Output
XCAL
(A2/3/R2313)
XCAL
XCAL
XCAL
XCAL
Output
YCAL
(A2/2/R1309)
YCAL