Fluke 900 - Manual (Page 86)

Maintenance FLUKE 900 SERVICE MANUAL
The rest have a common header; "F_MASK offset table". These blocks wiUbe referred to
with their individual headers: "duration 40 ns", "duration 80 ns" up to "duration 240 ns" or
simply "40ns", "80 ns", etc.
Each block consist of five columns, the first being pin number, the other four being
"offsets". In other words, each pin has four offsets labeled U-H, D-H, U-L, D-L.
NOTE: The first two columns in Limits Table Block are meaningless and should be
ignored.
5A.2.2 Calibration Standards
The main condition standard is that the absolute value of the offset for all pins should be
less or equal to 4. A board that fulfills this condition and passes aU tests in the selftest is
considered calibrated and does not need any further adjustments.
NOTE: the first block (Limits table) does not need to fulfill this condition if all other
blocks are OK.
In each block, the line with the biggest offset is marked with a ">" character so only such
lines need to be checked. This rule does not apply to limits table block which has to be
checked line after line if needed.
5.4.2.3 HSB Component Placement
There are seven white rectangles outlined on the HS Board that are called F1,F2,..J^. FI
is located at the bottom, then F2 and so on. Within each rectangle there are fom identical
fields designated UBl, UB2, UB3, UB4. A 74ALS09 chip is placed between UB2 and
UB3. Each UB field has a place for an additional resistor and capacitor (see fig. 1).
Whenever the word "resistor" or "capacitor" is used in this section, it relates to these
additional components. The words channel, line and pin are used to mean one of the 28
signal paths.
The following table relates the 28 channels to the components in the UB fields.
Area UBl UB2 UB3 UB4
F7 1 27 28 2
F6 4 24 26 3
F5 5 23 25 6
F4 20 9 22 7
F3 21 19 10 8
F2 16 12 18 11
FI 15 13 17 14
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