[time-nuts] Brooks Shera GPS Controller Help

Brendan Minish ei6iz.brendan at gmail.com
Wed Jan 17 18:45:11 EST 2007


Here 
http://www.rt66.com/~shera/setup_notes.html
In the troubleshooting section there's a note about A mysterious
problem.

I had this issue, I Wonder could it be related to your issue? In any
case the fix does not hurt so worth a try?  


On Wed, 2007-01-17 at 17:05 -0600, Jason Rabel wrote:
> Checked that today, getting 315.5KHz (A&A Board - P3 pins 1&2 jumpered).
> 
> I pulled all the chips, just to make sure I didn't have any bent/broken
> pins. Reflowed every pin on the board so there would be no doubt in my mind
> that there were any bad joints. Replaced chips.... Same problem I've been
> having.
> 
> I just checked my frequency bits again, the full range on the OCXO EFC from
> 0-6V gives me 4,999,997.9 to 5,000,002.4 Hz (4.5 Hz total difference). Each
> volt shifts about .75 Hz (I measured from one volt to the next, but also
> just the simple division from the numbers I gave results in the same final
> number).
> 
> It's like it's not counting or detecting the phase properly or something.
> Maybe one of my chips is the incorrect model? Here's a list for everyone to
> compare theirs to.
> 
> U1&U3: TI  CD74HC4046AE
> U2:    ST  M74HC4520B1
> U5&U6: ST  M74HC166B1
> U4:    TI  CD74HCT4040E
> U7:        EXO 35M / 24.000M / KSS JAPAN
> 
> The PIC & DAC I got from Brooks, U10 is the Max233 (and not really related
> to the rest of the circuit).
> 
> 5:00 now, time to go home...
> 
> Jason
> 
> > Jason,
> > What divider output are you using? The typical input to the 
> > phase detector
> > should be between 312.5KHz and 625KHz and an appropriate 
> > jumper has to be
> > installed on the divider header on the A at A board to tie the 
> > selected divider
> > output to the phase detector. Sounds like you aren't getting 
> > a good clock
> > into the phase counter reset.
> > Hope this helps,
> > Richard
> 
> 
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