(red) MMDVM board failures

 I have bought a few different MMDVM boards to run with Raspberry Pi,  such as JumboSpot, the dual HAT boards  and some red colour S56AL clones.

These red boards I found to be best for P25, as the other boards typically have too much frequency drift, which makes the other boards like JumboSpot work fine for DMR usage, but for P25 usage it is much more critical, otherwise you get lots of artifacts in the voice transmissions.

Anyway, the first board I bought, was working great for P25, after 6 months it suddenly stopped receiving transmissions from the RF modem receiver, it just ignores  any transmission, the Receive light no longer lights up, I spent considerable time looking for solder faults under magnifying glass, comparing the circuit diagram to the board, followed the path, but could not fix it. So I bought another two of the red  boards,  tested them,  they were working, great I put them both to work, so I could run two different frequency P25 hotspots, about a month or so, one of them dies,  no receive from the radio modem side, then after 4 months the second board dies, again, same fault, receiver stops decoding signals.

All three boards transmit perfectly. I also configured and tested these boards for DMR operation and it is the same deal, receiver does not work,  transmits ok in DMR mode. I know it is not the mode. All three boards are using the onboard ceramic antenna, so it is not a case of RF overload, as it is same IC's and circuit used on my JumboSpot boards. 

These boards are marked as S56AL v2.1 and coloured red.  These are NOT boards from Alex S56AL,  this red board is a chinese clone board based on S56AL's circuit design. 

As it stands, I still running these boards in Tx mode, I can monitor 3 different P25 TG's at once now, as none of the boards can receive, so they won't be talking to each other. In the meantime, I am now looking for another MMDVM board that is stable enough for P25 usage and won't fail after a few months.

Here are the pics of the "Red" board. Note: JP1 to external SMA socket antenna is not bridged.

Also Note I added the 4 pin IDC sockets to my boards so I can plugin a OLED display