Does anyone recognize this board, is it a gpsdo?

[eevjohn]

Hello Denmark


But..
1) Where on the board do I connect which wires?

The “terminal” signals on the NEC board are TTL levels and must be converted to RS232 voltage levels.
I used a dual bi-directional driver MAX232N.
Be sure to add the 0.1 capacitors C1 – C4 as per datasheet.
Connect the MAX232 TTL inputs and outputs to the NEC board signals near connector Z5.
Connector Z2 is on the other side of the board, but solder points near Z5 were easier for me.

Z2 connector pin 33 is TOD TX Data; no handshake required.  TXD every second.
Z2 connector pin 29 is RX Data from the user terminal
Z2 connector pin 31 is TX Data from the NEC.

I used tiny “wire wrap” wire and just tack soldered to the pin side of the small SMD components which connect to Z2.
The connector that I have at NEC board connector position Z1 is just a tie point. My connector does not connect with any Z1 signals.
Be very quick with your soldering.

TOD output goes to pin 11 of MAX232
TXD goes to pin 10 of MAX232
RXD goes to pin 9 of MAX232.
I used 100R resistors in series with each signal to add a degree of isolation with each connection.

See photo.


2) Do I need anything in between the board and the COM cable?

Yes – add RS232 signal conversion as above.

3) Do I need to change the COM port config in Windows (7) or in U-center / Lady Heather?

Depends on particular PC and Terminal Software.
TOD signal is 4800 baud 8N1
Service Port is 115200 baud 8N1
I used both COM 1 and COM 4 on my ASUS WIN10 Laptop with Terminal Program “Termite 3.4”.
You will probably have to experiment a little.

You can only “talk” to the NEC Board software, not to the uBlox receiver module.
That would require a separate terminal connection on the uBlox module.
I have no experience with this, and it was not required for me, as to a degree, the NEC board interprets and reports the signal levels etc.

Good luck.

[ShadowLight]

Hello guys,

I know this subject has come silent, so let me know if I should post my own subject. But thing is, I think there is only this subject about this NEC GPSDO here...

I recently bought a board from eBay, it came without the OCXO. I powered the board, it works (there is a PPS signal at the LEA-5T). So I'm now looking for an oscillator. The Epson Toycon looks to have a control voltage ranging between 0-10v, centered at 5v. I was looking at some MV-180, but they are expecting a control voltage between 0-5v. Would the board be able to "learn" the control voltage, would it be safe for the MV-180? Or is there another reference I should be looking at?

Remi.

EDIT 2023.07.14: The answer is yes. I bought a FEI FE-180 OCXO on eBay, the control voltage starts a bit high but stabilizes around 2.8 volts. Lady Heather reports everything good after a while.