loss of signal on QUattro ultima

[RDNut]

We have a Quattro ultima that suddenly lost signal in the middle of a run, I infused A Juice at 10 ul/min and could see a little bit of the 2035 in both ms1 and ms2. After venting and powercycling the instrument all masses looked good and I made some injections using a method we run twice a week. It looked great for a few injections then the signal died again, the A juice showed the same symptoms. After venting and powercycling it again worked for about a half an hour and died. Anyone have any pointers on where in the instrument the problem might be? All the readbacks look normal, parking either MS1 or ms2 at 2000 the rf voltage flips around 350 to 500 as it normally does. The detector readbacks all look okay too.

[mhr311]

Sounds like a power supply going in and out. Check the low voltage supplies (near the front, accessible from side panel) as well as the Photomultiplier voltage supply found on the short card near the vacuum PCB. Note reseat that card and check the BNC HV connector. Is the 84V present when signal is lost?