Hameg HM 303-5, Service Manual

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Subject to change without notice 26
ADJUSTMENT PROCEDURE
30MHz Standard Oscilloscope HM303-
5
WARNING
The Instrument must be disconnected from the mains power supply whenever you open
the case, repair or exchange parts.
HIGH VOLTAGE WARNING!
Hazardous High Voltage of up to 2,000 Volts is present inside this Instrument. The areas particularly
affected by High Voltage are the high voltage circuit on the PS-board, the CRT-board and the CRT-
socket.
SERVICE AND ADJUSTMENT
• of this instrument should only be performed in accordance and in conjunction with the operating
manual and the WARNINGS contained therein.
• should only be performed by suitable qualified and experienced service personnel, or should be
referred to one of the HAMEG companies listed on the rear cover of the manual.
Test Instruments required:
1) Scope Tester HZ60-2.
2) Constant amplitude sinewave generator, 20Hz - 250MHz, output 5mV - 5V into 50
Ω
,
preferably with 20dB attenuation (e.g. HM8133, TEK SG502 + TEK SG503).
3) Amplitude Calibrator with 1kHz squarewave output and 600
Ω
impedance, risetime faster than
150ns.Output voltage 2mV - 20Volts in 1-2-5 sequence for 4 divisions display amplitude
(e.g. HZ62, TEK PG506).
4) Time mark generator from 5ns/div to 5s/div. Output min. 10mV into 50
Ω
(e.g. HZ62, TEK TG501).
5) Pre-attenuator 2:1 (1M
Ω
, 12-48pF), e.g. HZ20.
6) 50
Ω
BNC through termination, e.g. HZ22.
7) 2 BNC-cables, 50
Ω
, e.g. HZ34.
8) BNC-T-connector.
9) Oscilloscope probe 10:1, with exactly 9M
Ω
series resistance and compensated
for test oscilloscope mentioned under 10).
10) Oscilloscope 100MHz, 5mV/div to 5V/div, e.g. HM1005.
11) Trimming/adjusting tool.
12) Variable output safety insulation transformer.
13) Video signal generator with positive and negative signal output.
14) Yt-EPROM HM1007.
This procedure covers all adjustments and the most important - but not all - performance checks.
The correct sequence of all adjustment steps must be strictly followed.
Exact adjustment is only possible when any influence of the earths‘ magnetic field has been
compensated with the trimmer marked TR (trace rotation).
All adjustments should only be performed by qualified and experienced personnel. This is particularly
important for adjustments in the high voltage section of the instrument.