Out of the blue, I am suddenly dealing with this "too many listeners on the GPIB" error, and my PC could no longer find any intsruments in NI-MAX. I have a GPIB-USB-HS connected to my PC, and 8 instruments (few HP4142b, Keithley instruments, power meter, etc) daisy-chained with various GPIB cables..I was able to control them in LabVIEW and was having no issue with it for months.
Then yesterday, LabVIEW (I have 2012) suddenly hung when I was trying to access one of the instruments (went into "not responding" state). Upon recovering, it could no longer see any of my GPIB instruments in the drop down menu. I restarted LabVIEW, but still got the same thing..could no longer see my GPIB instruments. I restarted the PC, and same issue. Then I could no longer see any GPIB instruments in NI-MAX. I have spent a few hours debugging this, trying different setups, connecting to 1 or 2 instrument at a time..now with this new configuration I am able to get it to see 7 of my instruments, but not all 8. I have one Keithley 7001 system it does not seem to like anymore...when i connect it to the rest of the GPIB instruments, I get the "too many listeners" error and can't see any instruments in MAX. Odd because I have two of these 7001s in my setup, and it is seems ok connecting to one but not the other.
Overall this is all really strange and i cannot figure out what could be the issue...would appreciate any suggestions/tips.
things i have checked/tried
-all GPIB instruments have unique addresses..there are no conflicts. as i mentioned, things were working fine before..suddenly they weren't.
-doesn't appear to be a GPIB cable issue. i have tried different cables..same cable will be ok connecting to one instrument, but when i use it connect to this particular Keitlhley instead, none of the instruments can be found.
Also, i just noticed something, don't know if it's important.. for my GPIB-USB-HS, the "Ready" light seems to always glow amber...it is never green. And the "Active" light never seems to come on...even when i'm sending commands to instruments. Not sure if this matters or not.