SECTION E : MAINTENANCE , REPAIR AND CALIBRATION
E-1.
General
The AMPTEC RESEARCH 620UK Ohmmeter is shown in PCB block diagram form on page 17.
The AMPTEC 620 Series Igniter Tester uses modern solid-state semiconductors exclusively and digital CMOS
circuits extensively to minimize power requirements and make battery operation useful and practical. AMPTEC
also maintains a
620UK spare PCB inventory
and it’s customer service department can also provide
additional assistance in the trouble shooting process.
E-2.
Troubleshooting Only by Authorised Personnel
Since the 620 Ohmmeter is used to test potential deadly explosive force detonators and warheads of missiles
etc.,
personnel that are not qualified to make such electrical repairs on the 620UK Tester should not even
attempt to remove the calibration access screws or open the main panel or effect any repair whatsoever
.
Apparent 620 Tester malfunctions can sometimes be the result of bad test lead/connection wiring, wrong
connections, misinterpretation of specifications, low battery levels, and in rare cases due to an incomplete
understanding of the instrument and how to use it. A thorough review of the operating instructions for this
instrument is recommended prior to any component replacement. Check to be sure that cables and other test
equipment are in good working order before attempting to troubleshoot the 620 series igniter tester .
If you turn on
the AMPTEC 620UK,
display does not come on
, it may indicate the batteries need
replacing. If the 620UK exhibits problems that cannot be eliminated by reviewing Chapters B and D, the
following guidelines have been established to help solve the problem.
E-3.
CIRCUIT BOARD OPERATION OVERVIEW
There are two main internal printed circuit boards that perform the AMPTEC 620UK “Digital Ohmmeter”
resistance measurement. The AMPTEC 620UK Explosive Safety Ohmmeter uses an
independently certified
“intrinsically safe”
constant current source (current source PCB). When the intrinsically safe current constant
source is combined with the ohmmeter's digital voltmeter PCB electronics a stable DC resistance measurement
for 0.0001 Ohms to 2.0 Megohms is provided. The digital voltmeter electronics (DVM PCB) uses a high input
impedance sense circuit. The digital voltmeter circuit draws very little current when it measures the DC voltage
drop across the “resistance under test”. The worst case test current (<8mA or less) for each range is indicated on
the AMPTEC 620UK Explosive Safety Ohmmeter/ Igniter Circuit Tester specification page of this manual
(Section B). The AMPTEC 620UK DVM PCB slides in (slot)
above
the Failsafe Current Source PCB.
The
620UK Ohmmeter’s front panel security screws must be removed to access either the DVM PCB (upper slot)
or the Constant Current Source PCB (lower slot).
and the
15
