Sorry, that should have been '10base2 ethernet card'
On Sun, Dec 22, 2019 at 11:16 PM Adrian Godwin <artgod...@gmail.com> wrote: > Voltage converter might be one of these : > > https://www.we-online.com/catalog/datasheet/177920521.pdf > > You can also sometimes find a similar device on an old 10baseT ethernet > card, where it generates a -9V supply. > > On Sun, Dec 22, 2019 at 7:04 PM Brian Lloyd <br...@lloyd.aero> wrote: > >> >> >> On 11/26/19 09:28, x...@darksmile.net wrote: >> > Hello everyone, >> > >> > Does anyone here know about this item: >> > >> > >> https://www.ebay.com/itm/Brand-New-NTP-Time-Server-GPSDO-GPS-Disciplined-Oscillator-GPS-Clock/362758051388?hash=item547610963c:g:yFIAAOSwgztdgfM9 >> > >> > >> > George, N2FGX >> >> OK, I ordered one. I missed the part about the 10MHz output being >> "optional". (Optional? Really?) So I ordered one and it arrived 2 days >> ago. Delivery took about 3 weeks. Looks nice, well packed, no damage. It >> includes an active GPS antenna with about 20' of RG174 and a 12VDC >> wall-wart. Unit, antenna, and PSU, nothing else. No doc and no software. >> No problem ... so far. >> >> Plugged it in. Power supply LED comes on and the Sync LED is flashing at >> about 2Hz. About 20 seconds later the SV LED comes on. about 2 minutes >> later the Sync switches to 1Hz. I am guessing it has achieved some sort >> of lock. I connect the 10MHz output to my FA-2. Of course, no 10MHz >> output. (More on this later.) I plugged it into the network. Looked at >> my DHCP server. No IP address assigned. Huh. How do I find this thing on >> my network? >> >> eBay message back to the seller. Seller sends me a link to a zip file >> with the software and doc. The first 'uh oh' is that all the file names >> are in mandarin. I must admit, I find <mandarin>.pdf and <mandarin>.exe >> amusing. I have an old laptop that dual-boots Linux and Windows just for >> this sort of thing, i.e. annoying software that only runs on Windows. I >> extract everything from the zip file and try things out. One of the >> programs shows just an ip address of 192.168.0.100 and has three windows >> separated into dotted-quads. Could this be the tool that sets the IP >> address, subnet mask, and gateway? I run the PDF that opens with a >> picture of the unit through google translate. OK, yes, that is what the >> program does. There is a picture of the window and, guessing at the >> examples, I was right, IP addr, mask, and gateway. With 5 buttons to >> click on in varying orders, it tooks me several tries to finally get it >> to change its IP address to one on my network. It is now pingable. >> >> I look at some of the other programs. These are mostly in English, being >> open software, and do things like let you look at the status of the GPS >> receiver. After successfully setting the IP address of the unit, I was >> able to run the utility 'PowerGPS.exe' and have it report GPS status >> from the box. >> >> So I pointed ntp on my linux server at the box as a server. It synced >> right up and chose it as the primary ntp source. Clearly it works just >> peachy as an NTP server and is running in my network that way. Now to >> tackle the lack of 10MHz output. >> >> Opening up the box it clearly has a 10MHz OCXO so getting something out >> the 10MHz BNC connector should be fairly straight-forward. Examining the >> bottom of the board, the path from the OCXO to the 10MHz BNC output is >> pretty clear. It goes through a single buffer op-amp and then drives the >> BNC jack. The only problem is, the op-amp is missing. The pads are for >> an SO-8 package. Following the traces it is pretty clear it is a >> standard, single-op-amp pinout, i.e. : >> >> 1. n/c (null) >> 2. inverting input >> 3. non-inverting input >> 4. V- >> 5. n/c (null) >> 6. output >> 7. V+ >> 8. n/c (null) >> >> Lots of parts could go there. Looks to me like it should probably be >> something like an LT1227. The op-amp is operated at a gain of 2 with a >> 100ohm FB resistor and 100ohm to ground. This should be pretty stable >> with 100ohm pretty much swamping any parasitic capacitance in the FB >> loop. The input is a 300 ohm/300ohm voltage divider so the overall gain >> of the stage is unity. >> >> Input to the buffer from the OCXO is capacitively-coupled as is the >> output. There is a 50ohm resistor in series with the output. The >> unloaded voltage output of the OCXO is a 3.5V positive square wave. >> After passing through the buffer it is probably supposed to approximate >> a 3V p-p sine wave. (At least, that is what the marketing verbiage >> suggests.) >> >> The board is already populated with linear +5v and -5v regulators (74L08 >> and 74L09 respectively) and associated bypass/filtering. +5v is present >> at pin7. No -5v is present. Tracing the board back to the source of the >> -V at the input to the -5v regulator, one arrives at an empty 4-pin >> through-hole area marked u14. This has +7.5V on pin 2 which also feeds >> the input to the +5V regulator. Pin 3 is the -V output that feeds the >> input to the negative analog regulator. So the 64-dollar question is: >> does anyone know of a chip/module that is a 4-pin, 0.1" pin spacing, >> single-output, inverting regulator module, producing -7V from a +7V >> input? I need to find something like that to populate this board and get >> the 10MHz output. I haven't been able to find anything on Mouser or >> Digi-Key. I am guessing that this is something that already exists as a >> module but ... >> >> Yes, I have asked the seller about the parts to populate the board or >> the option of returning it and getting one already populated. If the >> seller tells me to go pound sand I would like to manage to make this >> work anyway. >> >> Hmm ... if I DC couple the input and run the op-amp with a single-ended >> +5v supply, it might work without the negative supply at all. My only >> worry would be latch-up because the input would be going right to the >> negative rail and approaching within 1.5V of the positive rail. OTOH, >> most op-amps now are pretty immune to latch-up. Just thinking aloud >> here. I am sure someone here has some ideas about getting this to work. >> >> Thanks in advance for humoring me. >> >> >> -- >> >> >>  <https://www.lloyd.aero> >> >> Brian Lloyd >> 706 Flightline >> Spring Branch, TX 78070 >> br...@lloyd.aero <mailto://br...@lloyd.aero> >> +1.210.802.8359 >> >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@lists.febo.com >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. >> > _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.