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High current read back for 40K amplifier #205

Open hlym opened 4 years ago

hlym commented 4 years ago

Biasing the the 40K amp with SMuRF with a nominal voltage gate voltage read back a current of 66 mA. We checked the current drawn with a bench top amplifier and it was normal (~15 mA). Turning amplifier bias on/off and restarting pysmurf session did not fix the problem. Had to power cycle the server.

swh76 commented 4 years ago

@hlym This sounds like a known hardware issue on your RTM (we call this the "RTM hiccup"). If this happens again, if you're able to, could you please put a multimeter on the +12V output of the cryostat card (which you probably use to power your warm LNA) ; if it is the known RTM hardware problem you'll see the +12V output is hiccuping on and off.

Rebooting the server shouldn't matter - probably it was resolved by running shawnhammer after reboot (but you never know...). We need to fix your RTM (I saw you put in a request for that to Ryan), but until then if you run into this again and shawnhammer doesn't seem to be working, I usually unplug the crate, wait for 30 sec, the plug it back in and hammer. I think some regulators on the RTM latch and power sometimes has to be completely removed to get them to unlatch.