KerberosSDR hardware fault: DIP switches


Further to my ‘Kraken software on a KerberosSDR with Pi3’ post:
The eBay seller very kindly refunded me my money and said I could keep the KerberosSDR. :smiley:
So, now I would like to repair it.

The fault is that Receiver #2 isn’t recognised by the software, e.g. when trying to update the EEPROM.

I have established that each of the four DIP switches are short-circuit when they are closed and the LEDs go on and off when the KerberosSDR is powered on and each switch is toggled.

Can anyone tell me what the resistance to ground should be for each of the terminals of the DIP switches?
I ask because I was expecting one side of each of the DIP switches to be connected to ground.
However, there is 990 ohms to ground on the contacts on the inner side of the PCB.
(With 3.5 Meg ohms on the outer sides of each DIP switch.)
With all four switches having the same resistance to ground, I suspect that 990 ohms (perhaps 1K0) is correct. But it would be good to have this confirmed.

All advice welcome.


The DIP switch circuitry appears to be working correctly for all four receivers.

I have found some voltage anomalies within the Receiver #2 circuitry when compared with the other three receivers.

The voltage on L24 (Rx 2) is 0.3V whereas the voltages on L34 (Rx 1), L57 (Rx 3), and L79 (Rx 4) are all 1.2V.

Within the screening can, there is 3.2V at R49 (Rx 2) but only 0.1V at R68 (Rx 1).

Also, the Rx 2 circuitry within the screening can may be running slightly warmer than the circuitry within the other three cans.

Does anyone have a circuit diagram for the KerberosSDR so that I may make further investigations?

Many thanks.