Chet make sure all the components are flush to the PCB especially the
input coil and the drain resistor. If everything looks good then you
could have a damaged chip cap(s) in the source of the GaAs FET.
The cover should have no effect on tuning once the above is addressed.
G/L,
John
N2HMM
> I thought this preamp was working OK for a few months, but it is not now.
>
> When it is out of its die-cast box, it seems to hear and tune up just
> fine.
> But when I put it back into its box, it still outputs a higher level of
> background noise, but the input signals are not amplified.
> If I just crack the lid a bit, it again hears OK, but when completely shut
> it does not.
>
> Input detuning? But there is not way to tune it when it is in the box.
>
> Any ideas??
>
> Chet, N8RA
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