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FEC200 Maintenance Hints

The first step is to eliminate the PC and its interface, the DC supplies, and the relays. PC and its interface, the DC supplies, and the relays.

Since the PC is almost completely stock, you can test it independently to see if it runs some general purpose software.

The relays can be checked thoroughly using the “RELAYS” diagnostic. Most problems will be stuck reeds. This can be checked just by selecting “all open” and testing them with an Ohm-meter. If you suspect an open relay, you can select any type of test and check the relays that should be closed. The program tells you which ones they are.

The computer interface is a little more complicated. If you prove that the interface is bad, you will have to try replacing both boards to find which is bad.

All of the diagnostic routines use the interface to some degree. If two or more unrelated diagnostics (such as HANDLER and RELAYS) both fail, you should suspect the interface.

If just one diagnostic fails, you can never be perfectly sure whether the problem is the other board (s) involved or just the particular output register on the interface board. This makes the B621 a good candidate for a spare board.


There is a diagnostic routine to check all of the bin drivers, the EOT driver, and the start test circuit. It is best to use the manual station for this test. You can see the outputs on the LED lamps and use the push buttons to make a start test pulse. Also this eliminates the handler itself as a problem. You should know that the four B502 interface boards and the sockets they are in are identical EXCEPT that each board is jumpered for the station it serves.


If the tester does not polarize correctly, the problem must be the B368 polarity sensor, the associated relays or the computer interface. It’s a good idea to write a program with NO TESTS. This program will just test polarity and Kelvin contacts and show the results on the computer screen.


The SELFTEST, which runs all the time, compares the DAC1 output with the corresponding ADC reading. If this test fails, the problem must be the B500, B501, or the computer interface. On the other hand, if this test does not fail, you know that the DAC1 and the ADC both work. DAC1 is used to program the forcing conditions for all tests.


Always determine which tests work ok as well as which ones do not. Also see if the problem is associated with forcing currents above or below 4mA and readout voltages above or below 16V. This will help greatly in narrowing down the problem.


You should determine if the testing problem is with the forcing supply or the readout. Use your scope to see if the forcing supply for the test involved is working. For constant current tests, you may want to use a resistor as the DUT. If you see the voltage on the resistor you can calculate the current by Ohms law. Scope sync is available. See SCOPE SYNC.


The boards used by the AC tests are B500, B552, B530, and the computer interface. You can easily checkout the B500 AC capability using the diagnostic SINES.



Scope Sync is available for all tests and most diagnostics. The sync comes from TTL drivers and is “low” going. You can set it to occur on any test being done on the “current” station. SYNC1 occurs as the forcing condition is turned on. SYNC2 occurs at the time that the internal ADC samples its reading.

SYNC1 3 SYNC2 3 (Test 3 on current station)
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Last Updated September 12, 2007
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