I just got a new BGTBL GNSSDO, the successor to the GPSDO, with an used (OEM-)specific OCXO (C-MAC 48S1164).
Just would like you to know, that the parts configuration and placement does and may vary depending on the original OCXOs used. This might make it almost "impossible" to replace a defective (original) OCXO with another one without adding additional parts of sometimes
unknow specs, dependig what OCXO was used originally by BG7TBL. The major problem is, that there are no schematics "in the wild" or supplied, which could be used. The latest incarnation of the GPSDO, now called GNSSDO, has a new motherboard (2021-06-10) to adapt to all kinds of (used) OCXOs which might be available right now on the used market. Unfortunately many rare OEM OCXOs are not documented, even when searching the net intensively, and may feature - eventually - a different PIN layout or other variations in specs, which make it almost impossible to find a direct replacement in those cases. Mine i.e. got an OEM specific C-MAC OCXO, which seems to fluctuate quite heavily below the 10MHz mark, Unfortunately the OP-amp multiplier had been set to x3 by BG7TBL already, but my fully functional replacement OCXO (Oscilloquartz 8663-XS) does fit mechanically but not electrically exactly for this reason, because some parts are missing or are new on the board (solder pads are unpopulated, no values given etc.) for substituting the OCXO. Because of the missing parts no 10MHz signal is been produced, although the Oscilloquartz OCXO 8663-XS is fully functional as tested several times. I already looked around for another replacement OCXO (same kind), but no luck...
What makes me wonder is, that the label on the GPS-chip has been removed although it is supposed to be an "Ublox NEA M8N " as stated by the seller, which told me, that he had checked this himself with the Ublox control software. I will have to check this out later on too. Some Ublox clones identify themselvs as Ublox chips but dont have the corresponding flash on board as tested by others already.
Sending it back from Europe costs a lot too and does not make this feasible. Note: I will add some photos of the "new" board if I got the time to do it.
If you look at page 1 of this thread, you will find an ever changing list of different board layouts, which seems to continue "endlessly" up to the current date. Many OCXOs have an identical PIN layout and usage, but some vary quite a bit not only by size.
PS.: Latest units have become quite expensive for such a unit because they now reach about appr. €200 after importing them to Europe.
The factory installed solder bridge on the X3 pads have beeen already removed on the photo of the PCB.