How To Find And Replace Bad Hybrid Card Relays

All shorts test fail on all boards and yesterday they’re fine. Before we debug our fixture, run diagnostic for the system and find out one of the hybrid cards we used for the fixture has bad relays. We swapped the hybrid card and it moved to the new slot. While waiting for the service people to ship a new card (these days Agilent don’t troubleshoot and replace relays any more), we decided to find the relay and replace it ourselves so we can get the development going.

1. We know the relay # and the tests they failed.

card failed      card moved

2. Now the bad card with K7F failure moved to module 2, slot 2a. Since this is double density hybrid card, notice the 2a because there are 2 K7F (A & B).


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3. We should open the service manual, look up the test #, subtest # and find the relays group, sometimes it’s easy to find K7F is the bad one, sometimes it’s not. So here is the service manual.

service manual     test numbers

test 3986     subtest 51

4. Now let’s look at the location of the K7F and hope it is the one. Search for K7F.

search k7f     K7F A

Remove the hybrid card and locate the K7F A. Measure pin 1 and 4 to see if they’re shorted, if they are, then replace the K7F A.

K7F A on the back side     relay has shorts

Use solder sucker and soldering iron to remove the relay, pretty easy, notice the pin 1 when install the new one, 1 side is sharp, 1 side is rounded.

pin 1     bad relay removed

Put a new one, make sure the new one has no shorts, solder well all 4 pins – again check for the orientation of the relay, round edge vs sharp edge.

Put it back and run diagnostic again, it should pass nicely. Now we’re up and running again until the new card comes. The next thing is how to find which probes cause the system hybrid card to fail.



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