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Callbration Procedure (Adjustments)-DM 505
ADJUSTMENTS
Introduction
PROCEDURE
This procedure need not be performed unless the
instrument fails
t o
meet the performance requirements of
I-
Adiwt
the +15m7S
the electrical characteristics listed in the Specification
a. Set the voltmeter to the 20 Vdc range.
section. Adjustment is generally required after a repair has
been made or after long time intervals in which normal
aging of components
may affect instrument accuracy.
b. Connect the voltmeter positive lead to the DM 505
H5.75
V t e a point and the negative lead to TP1521 (LO).
To ensure instrument accuracy, check the calibration
every 1000 hours of operation or every six months if used
c. EXAMINE-that
the voltmeter reads +15.75 Vdc
infrequently.
f
0.08
V.
Tektronix, I
nc.
provides complete instrument repair
d. ADJUST-R1021, the+15.75
V ADJ,for avoltmeter
and calibration at local Field Service Centers and at the
reading of +15.~5
v
f0.05
V.
Factory Service Center. Contact your local Tektronix Field
Office or representative for
further
information.
e. Disconnect the voltmeter from the DM 505.
Test Equlpmeml Required
2. Adjust the Clock Frquency
Test equipment used for adj ustrnent of the DM 505 is
a.
Set the counterto Frequency, 10 Hz Resolution, and
listed in the beginning of the Calibration section. All test
Display Time fully ccw.
equipment is assumed to be correctly calibrated and
operating within specifications.
b. Connect the counter input lead
to
the CLK test
point.
A X I probe
may be used,
if desired.
Preparation
Connect the DM 505 to the power module via the
flexible plug-in extender. To gain access t o
the
ad-
justments, remove the left side cover
of
the DM 505 by
pulling the
rear
of the side cover
outward from the
instrument. Then remove the large metal shield attached
to a standoff in the center of
the
instrument. If desired,
most adjustments may be made through the holes in the
metal shields using an insulated adjustment tool. Adjust-
ment locations are shown in the illustration located in the
pullout pages at the rear
of
this manual.
Connect the test equipment
and
the power module to a
suitable line voltage source. Turn on the power module
and the test equipment; allow at least 30 minutes far
equipment warm up and stabilization. Set the INPUT EXT-
INT to the out (EXT) position.
Make
adjustments at an
ambient temperature of
+21°C
to
+25*C.
Perform ad-
justments in the order given, since some adjustments
interact with others. Interactions are noted in the
procedure. Refer to the adjustment location page (in the
Diagrams and illustrations section).
c. EXAMINE-that
the counter reads 20.68 kHz to
20.28
kHz.
d. ADJUST-R1202,
CLOCK FREQ ADJ, for a fre-
quency of ZQ.48 kHz
r t 0 . 0 5
kHz.
e. Disconnect the counter.
3.
Adjust Oc Zero
a. Press the VOLTS
DC
button and the
200
mV range
button.
b. Short
the
VOLTS/n and LOW input connectors
together with the dual banana plug shorting bar.
c.
EXAMINE-that
the DM 505 display reads 00.0
rto.
1 .
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