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Re: Intermittent Loss of Pre-Driver signal


 

Hi all, Now I'm not sure if this would work. Maybe someone with more knowledge?about FET's can comment.
Attached is the data sheet of the factory FET
Also attached is what I found that may be a possible replacement that is more robust. Since this is an RF
component, I'm not sure. Judging by the physical size of that resistor in the picture, this TO-247 case FET should?
physically fit.

Any comments?

Factory? RD01MUS1
Possible replacement? ?IRFP260NPbF

Bob W4JFA

On Thu, Nov 28, 2024 at 11:28?AM Steve G4ALG via <steve=[email protected]> wrote:
Update: New FET received & old FET removed
?
The new FET arrived today, ahead of the de-solder wick.? Upon inspection, I was pleased to see that the FET 'tab' and 'source' connections are made from a single piece of metal, which is clearly visible from the underside of the device.

This knowledge helped me in two ways.? Firstly, the source terminal on my IC-7000 had to be soldered to ground via the tab terminal, if not via the pad under the source terminal.? ?Secondly, I now had confidence that heating the source terminal with the soldering iron would probably release the tab terminal also.??

So, armed with my 50 year-old Weller TCP soldering iron, I first heated the tab, and then quickly moved to heating the gate, source, and drain terminals, thereby releasing the FET from the board.? Actually, it didn't happen quite this cleanly because the device fell apart during de-soldering.? I was half expecting this to happen.

I then cleaned each pad of solder, a whisker at a time, by repeated application of a 'dry' soldering iron tip.??

Here is the result:

?
Note that the PTHs each side of the 56 ohm resistor look much nicer from this camera angle? :-)

I have since checked the FET PCB pads for continuity, and all look to be solid, with no solder bridges caused by my ham-fisted work with less than ideal tools.? Note that I still haven't removed the Main board from the rig.

And here is a photo of what's left of the dead FET:




I'm now planning the next part of the repair.? There does at least seem to be a good chance of installing the new FET without removing the Main board.? All would be suggestions greatly appreciated.? ?
?

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