Introduction; Preparation; Power Supply - Fluke PM6685 Service Manual

Introduction

Required Test Equipment
Type
DMM
HF synthesizer
Pulse generator
LF synthesizer
Oscilloscope
Passive probe
FET probe

Power supply

Power splitter
Feed-through termination
10 MHz reference
10 MHz reference
BNC-BNC cables
Screwdrivers
Table 6-1
Required test equipment.
* For adjustment of PM9691 and PM9692 Oven Oscillators only.
Note: Only calibrated instruments should be used.

Preparation

WARNING: Live parts and accessible terminals which
can be dangerous to life are always exposed inside
the unit when it is connected to line power. Use ex -
treme caution when handling, testing, or adjusting
the counter.
Before beginning the calibration adjustments, power up the instru -
ment and leave it on for at least 30 minutes to let it reach normal oper -
ating temperature.
Power Supply
CAUTION: If you adjust the +5 V trimmer you have to
adjust the complete instrument.
Setup
n
–
Remove the protective cover above the power module.
WARNING: The heat sink inside the power module is
connected to line power.
– Connect the counter to line power.
–
Switch on the counter.
– Press PRESET, then press ENTER.
NOTE: The backlight must be switched on during the adjust-
ment of the power module.
6-2 Introduction
Performance
Acc. 0.02% / Res. 1mV
3300 MHz
125 MHz / 2 ns rise/fall time
50 MHz / 20 Vpp
300 MHz / 2-channel
10:1, preferably 500 W (or well
compensated 10 MW)
300 MHz
12 V / 2 A
50 W / 4W
50 W
-7
1x10
-9
1x10 *
Different lengths
Torx 10 & 20
J3
Fuse
J4
J9
J10
1 5
Po wer
Mo d ul e
+5V adjust
6 14
TP15, +5
TP17, -7
J15
TP16, +15
Fig. 6-1
Test points and trimmer for the Power Supply.
Adjustment
n
–
Connect the DMM to test point TP15 = +5V and GND, (see
Fig. 6-2).
–
Adjust the +5V trim potentiometer inside the power module
until the DMM reads +5.10 ± 0.01 V.
– Check that the voltage between the test point TP23 = +5 V and
GND is +5.06 ± 0.03 V.
– Check that the unregulated voltage from the power module at
test point TP16 = +15 V is about +18 V.
–
Check that the unregulated voltage from the power module at
test point TP17 = –7 V is about –8 V.
– Reinstall the protective cover onto the power module.
TP22, +7
J16
TP20, -5.2
TP23, +5
TP21,+12V
J21
Load