View Full Version : SWL PSK-20 - Diagnostic help required (Please!)

08-21-2009, 08:37 AM

I built a Small Wonder Labs PSK-20 transceiver at Christmas, but never got it to work correctly.

If I TX using the PSK software, it shows almost 5W output into a dummy load, so that part seems to be working OK.

The problem is that it's always stuck in TX mode. Q10 is always hot (although the watt meter only shows power output when I TX in the software).

Dave (NN1G) advised me to check the voltage on U4 pins 5, 6 and 7 on TX and RX...

5 - 1.83v
6 - 1.71v
7 - 2.90v

5 - 1.87v
6 - 1.76v
7 - 2.90v

Dave told me that those numbers don't make sense as U4 is an op-amp. Since pin 5 (+ input) is higher than pin 6 (- input), the output should be high (12V).

I've swapped the two '1458 ICs over and it made no difference.

I'm very green when it comes to diagnosing circuits, but I've checked all the components are in the correct positions and I can't see any dodgy soldering.

Can anyone with some PSK-20 experience please help me?

I'd very much appreciate your help on where to look next.

08-21-2009, 08:42 AM
The manual can be found here:


And some troubleshooting guides can be found here (that I don't particularly understand I'm afraid):



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