Re: Something has been blown

Jerry Gaffke
 

Not very weird.  
First off, RV2 and RV3 are wired backwards, so fully clockwise is minimum bias voltage to the gates.
You must go through the adjustment procedure whenever the IRF510's get changed,
as each IRF510 is different.
The procedure to adjust RV2 and RV3 is here:  http://www.hfsignals.com/index.php/ubitx-tuneup/
Basically, start out fully clockwise on both, then with ptt pressed adjust one for an additional 100ma
of current draw into PA-PWR, and then the other for an additional 100ma.

If RV2 and/or RV3 get turned too far up, the heavy drain currents will quickly blow the IRF510.
It is a very quick transition as you are turning those pots from "about right" to "way too much". 

Jerry


On Fri, Jan 26, 2018 at 08:23 am, César EA3IAV wrote:
It is weird. I was adjusting the pa with the blue squares and the fuse blew.

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