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3721 fails to engage backplane switch

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Joined: September 23rd, 2014, 6:14 am
Country: United States

3721 fails to engage backplane switch

Post by jaime_g » January 25th, 2017, 10:33 am

Dear Web Forum,

I am using a 3706 System Switch with firmware version 1.41c. There are four 3721 relay cards installed in slots 1,2,3,4 and 6. A new application, I am developing in LabVIEW, uses the backplane switches (X911, X921) to be able to multiplex the first relay bank (X001-X004) and (X011-X014) to any of the relays in banks X005-X009, X010-X013, and X014-X020.

The configuration described above works as specified in the user manual for slots 2,3,4, and 6. However, backplane relay 1911 does not close for the 3721 SLOT 1 MUX1 relay bank. When using the 3706 Web application, backplane relays 1911-1917 for SLOT1 MUX1 do not close. When attempting to close the relays by clicking the mouse on them, the diagram on the Web app shows the backplane not making contact with the relay. Also, there is no clicking noise when the relay is energized.

In the enclosed - for SLOT1 MUX1 relay 1911 is shown as closed on the 3721 side but with no connection to the 3706 backplane. However, for SLOT1 MUX2, relay 1921 is show with connections to both the 32721 side and the 3706 backplane.

Is there a way to enable 3721 SLOT1 MUX1 to connect to the 3706 backplane? Is this an indication of a 3721 malfunction or perhaps a 3706 SLOT1 MUX1 connectivity issue? The DB50 cable integrity was verified and ruled out as possible root cause of this failure.

Your help is appreciated.

Jaime Arevalo
Test Engineer
Micropac Industries
PMTS-1_3706 Slot1 3721.png
PMTS-1_3706 Slot1 3721.png (118.19 KiB) Viewed 10621 times

Andrea C
Keithley Applications
Keithley Applications
Posts: 1323
Joined: October 15th, 2010, 10:35 am
Country: United States

Re: 3721 fails to engage backplane switch

Post by Andrea C » January 25th, 2017, 1:17 pm

For the 3721 card in slot1, is the interlock satisfied (bank 1: pins 33,50; bank 2: pins 1,34).
Any error messages?

If you move the particular 3721 card to a different slot, does the MUX1 backplane relay begin to work?
Conversely, if you put a verified card into slot1, does it stop working?


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