The .5 on the f connector is an issue and thats through the filter on top of the board made of traces and 3 caps. From Arthur's digging I would agree he found the chip or one that would work. But that chips voltages seem to match so most likely not the issue. What does the F connector measure to ground? A strike could have burned the internals of the F connector. Above the DC filer will be some form of current limiting. Maybe an inductor or resistor.
On Sat, Aug 5, 2017 at 12:00 AM, Chris Waldrup <kd4...@gmail.com> wrote: > Hi, > > I've changed the blown MMBT3904 in the antenna sense circuit and I still > have no 5V to the antenna. I measure 0.5V DC on the F connector. > There are two Murata filters (F2 and F3) on the RF path to the antenna. In > between the two silver colored filters is a 6 lead SOT package marked 51A. > The PCB silkscreen says Q13. > I have measured the following voltages on this part: > Pin 1= 0v > Pin 2= 0v > Pin 3= 0.749V > Pin 4= 4.892v > Pin 5= 0v > Pin 6= 3.417v > > The trace from pin 3 of this part goes to the F2 filter and the output of > F2 goes to the F connector. I'm getting 0.5V on the output of this filter. > I'm suspecting this Q13 part may be bad but I'm not sure what the part is. > Searching the net for 51A marking came up with a large 2 pin shottky which > this isn't. > > Chris > KD4PBJ > > > On Aug 4, 2017, at 5:27 PM, Chris Waldrup <kd4...@gmail.com> wrote: > > > > Thanks guys. > > I've opened up my T bolt and noticed a SOT23 packaged part has the top > blown off. > > The PPS BNC jack has U19 beside it. > > The next part is blown. Could someone take a closeup of the five parts > around U19? > > The intact parts are marked: > > 5Dz > > 1AM > > and two 2Az parts. > > > > > > Chris > > > >> On Aug 4, 2017, at 4:13 PM, Arthur Dent <golgarfrinc...@gmail.com> > wrote: > >> > >> Actually that isn't my photo I linked to but one I just Googled. That is > >> probably a board revision most people don't have but it was the first > one > >> I saw so I used it just to show that the GPS receiver is part of the > >> only circuit board and not another easily replaceable board like in some > >> other units. > >> > >> I just took a couple of photos of the later revision of the board for > >> anyone interested in seeing what might be fried. In the photo of the > >> top of the board the signal comes into a filter then to a 25db amp > >> marked AM50002 by Macom. Above the filter near the input is where the > >> decoupled +5VDC for the antenna is connected. If you are only reading > >> 0.5VDC, if your're lucky it might only be the amp is fried and that > >> could be an easy fix. If the 5VDC is ok with the amp input pin lifted, > >> it might be the only problem. I wouldn't bet on it though. The 4031 I > >> believe is a 1575.42 SAW filter > >> > >> The photo of the bottom of the receiver area shows a Sawtek filter and > >> other parts. At the bottom of the photo is C460, a feedthrough capacitor > >> and that might be where the receiver output is but where my Tbolts are > >> working I don't feel the need to look into whether you could connect > >> the output of a seperate GPS receiver there to make it work. > >> > >> I do have one Tbolt that has no oscillator. I brought the EFC and 10Mhz > >> connections to SMA connectors on the back so I can test other > oscillators > >> or GPSDOs that don't have an easy way to monitor of graph the stability > >> of those units and using Lady Heather gives me a good way to compare the > >> graphs to ones I'm used to. You might possibly be able to replace the > >> built-in receiver but it might be easier to buy a working Thunderbolt. > >> > >> > >> http://i906.photobucket.com/albums/ac262/rjb1998/GPS% > 20top%201_zpslgxunnyw.jpg > >> > >> http://i906.photobucket.com/albums/ac262/rjb1998/GPS% > 20bottom%201_zpschvruppt.jpg > >> _______________________________________________ > >> time-nuts mailing list -- time-nuts@febo.com > >> To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > >> and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.