All,
I sent out a request for help awhile ago for a locking problem I was having with my DD2 system. All of the suggestions I received were very helpful in troubleshooting. With additional observation we saw that associated with locking difficulty there was also a loss in signal for gradient shimming. This led us to the relays on the transmit side of the RF front end after we eliminated the lock XCVR by both checking outputs with a scope and swapping boards between systems.
Outputs on the 600MHz DDS system should be:
In the lock screen set lockpower to max & measure
*Lock Transmitter output: > 3Vpp
*Lock signal at the probe: >1.1V (50-ohm setting) and pulse has a width of 5 msec when lock scan ON or 50usec when off
(disconnect the cable that goes into the lock on the probe and connect it into a scope with 50 ohm setting and measure the output)
There are two relays implicated. They are available from RelComm Technologies in Salisbury, Maryland, part number RDL-SR005 for minimal investment. A small solder job is required to replace them. So far, it seems to have solved our problem.
Thanks for your input in troubleshooting,
Victoria
vbegue_at_eastman.com
Received on Fri Apr 27 2018 - 03:15:34 MST