Hi Szabolcs,
I have followed your pictures and... success! Thank you very much for your guidance. I had however to invest into a decent desoldering station considering the multi-layer PCB with metal holes otherwise I would have damaged the traces to remove the NVRAMs. I then successfully removed the batteries and did solder two wires to a battery holder that I glued on top of the NVRAMS. A few cycles of on/off, removed the CAL jumper, ran the self-cal then external cal easily and there you go, all tests now pass. Thanks a lot!
Cheers,
Christophe
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