LTC1872B problem

[Russlk]

Has anyone succesfully used the LTC1872B boost converter and have an idea why it would not work? I built a 9 V to 100 V boost circuit that worked but all subsequent attempts to use the device have failed. The IC just does nothing. Pin 1 is above 1/2 volt as required but the output is low so the FET never gets turned on. Linear Technology has no application assistance as far as I can tell and do not reply to emails.

 

[Oznog]

I've had no trouble getting ahold of Linear tech support. Their phone support is good too. As always, write down everything you observed, if a pin is not oscillating as intended know whether it is stuck high or low, etc. Have your protoboard in front of you and if at all possible hooked up with a scope available.