Re: Bitx40 from Chile


Sandeep Lohia
 

Agree with Jerry abt 'abt parasitic oscillation in the IRF510 while in RX mode'
Coz drain & source never gets disconnected here even in RX BITX, unlike other RF Power BJT design...
parasitic oscillation can also trigger if gate is dry solder or short in transformer...

Crosscheq with DVM if Drain & Source of IRF have become short...
( keep one finger on - 0 V ground & other finger on gate while testing )



'Repair & Reuse or Recycle E-Waste'

On Mar 1, 2017 11:38 PM, "Jerry Gaffke via Groups.Io" <jgaffke=yahoo.com@groups.io> wrote:

You are right, his initial post said 0.98A in RX mode, almost a factor of 10 too high.  I didn't read that closely enough.

He did say that the IRF510 was getting hot, which means it probably is not the transformer.  There was another thread here where our best guess was a parasitic oscillation in the IRF510 while in RX mode, which can apparently occur even when the gate bias into the IRF510 is shut down at 0 volts.    https://groups.io/g/BITX20/message/22548


Jerry, KE7ER


On Wed, Mar 1, 2017 at 09:24 am, Ashhar Farhan wrote:

The IRF510 wouldnt have powered up in the RX mode. It looks more like the PA transformer was or something else was shorting to the ground.

 

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