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Re: QMX: Filter issues


 

Stefan, that transistor appears to have suffered a gate-drain short. You can probably confirm that with an ohmmeter.

JZ KJ4A

On Tue, Jan 16, 2024 at 4:20?PM Stefan U. Hegner <db4st@...> wrote:
Hi Folks,

Am 15.01.24 um 22:00 schrieb Stefan U. Hegner:
>> [...] test that Q508 is turned on while receiving.? The source and
>> drain should be close to zero volts.
>
> Not so sure on this one: Drain 0.64V, Source 0.07V, Gate 0.69V - no
> matter what band I select. - Is this maybe the suspect? Strange, as
> there was no re-soldering in that vicinity.
>
> [...]
>
> But my interpretation would be a fried Q508 ... so change one BSS123
> MOSFET.
>
> Please confirm this diagnosis
>
As 0.64V at the drain is not close to 0V, I suspect the Q508 ... but I'd
appreciate some confirmation on my interpretation, if that is possible,
before ordering parts and heating up the soldering iron ... Thank you so
much.

Vy 73 & mni tnx

Stefan.

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