SLA> Naw, there are only two and I replaced em both.  One of the 820s was
SLA> shorted, but so was just about everything else in the tool (it is an oil
SLA> well logging tool).  They dump a high voltage pulse from an inductor into a
SLA> ultrasonic magnorestrictive transducer at 20 cps.  I don't seem to have
SLA> enough trigger pulse to make em work.  Would the 820 be more sensitive than

How is the trigger pulse generated and what does it look like right
now? If the original MOSFET was shorted, it probably also shorted
either drain or source to the gate. This might have killed the driver
circuit either by overloading it (short to ground) or by bypassing the
high voltage pulse directly into the driver....


SLA> the 840 with regard to the trigger pulse?  Most of these type tools use an
SLA> SCR; this is my first experience with a mosfet fired transmitter.


  Uwe.

-- 
Author: Uwe Zimmermann
  INET: [EMAIL PROTECTED]

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