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4250 Flow Meter
Section 5 Maintenance and Service
5.6 Preliminary
Troubleshooting Steps
5.6.1 If Serious Problems
Occur
5.6.2 Inspection Protocol
5-14
4. While still pressing the 4 and Exit Program keys, turn
the flow meter on again. Wait until the display reappears
before releasing the keys.
Pressing 4 and Exit Program may leave some values pro-
grammed into the flow meter's computer. If you want to remove
all programmed entries, hold down 1 and Clear Entry while
powering up the flow meter.
The following messages describe serious internal problems, indi-
cating service is required:
ROM CHECKSUM ERROR - or -
FOUND BAD RAM - CALL CUSTOMER SERVICE
If these messages appear, call the Teledyne Isco Customer
Service Department at (800) 228-4373.
Do not attempt to disassemble or repair the 4250 Flow Meter
(other than changing fuses) unless you are skilled in the evalu-
ation and repair of microprocessor-based circuitry. Teledyne
Isco recommends no attempt be made to disassemble or
repair the printer mechanism or display module.
The electronic circuitry of the 4250 is solid-state and its reli-
ability is high. If the unit should fail to operate properly, the
problem is most likely a mechanical failure. Items such as a
broken or intermittent connections in the power cable or wiring
harness or (rarely) poor electrical connection through keypad
switches should be suspected.
If you suspect an electronic problem, Teledyne Isco recommends
that you contact the Technical Service Department. Contact
information can be found on the Warranty page at the
back of this manual. Our Technical Service Department has
trained technicians and specially designed equipment necessary
for timely, efficient repair of the 4250 Flow Meter. If you still
wish to attempt repairs, the Customer Service Department is
available to provide additional advice and information on ser-
vicing.
When attempting to isolate problems within the unit, you should
assume that the CPU and memory are working properly until
attempts to find problems in the peripheral circuitry have been
exhausted.
This is for two reasons:
• The likelihood of failure is far greater on transistor drive
circuits (heavier currents are handled here), than on the
CPU or memory.
• The CPU and memory are not serviceable and must be
replaced if found to be faulty.
CAUTION
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Table of Contents
Troubleshooting
