[hpsdr] Pennylane problem (suspect hardware issue) - a few pointers needed

[Paul Fletcher]

Hi all,

I think I have a problem with my Pennylane board. The RF side of things 
seems to be working fine. However it looks like I have a problem on the mic 
input. I've substituted the board with a Penelope card and that work fine. 
The issue is the mic audio is heavily distorted with a lot of noise. If I 
select the line input the noise is still present (but obviously there is no 
mic audio). I have a Janus card that I could use to try to tie down the 
problem but I can't remember if this needs firmware updating or not or if 
it's just natively supported (I'm using Metis as the interface).

Looking at the circuit diagram the mic input is fairly simple as it just 
goes to the CODEC via a few passive components and then to the FPGA. I've 
had a good look at the board under a Loupe and there is nothing immediately 
obvious in terms of manufacturing defects. It did work fine but has now 
developed this fault. I don't think it's firmware related (running V1.4 
Pennylane) but I can't remember if this has happened after I upgraded to 
V1.4.

Any suggestions welcome (oh and it's nothing to do with the mic or the gain 
settings either - the same setup and settings works fine with Penelope).

73 Paul M1PAF