[time-nuts] Thunderbolt question

[paul swed]

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 <kd4pbj at 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 <kd4pbj at 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 <golgarfrincham at 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
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