[time-nuts] Brooks Shera GPS Controller Help

[Jason Rabel]

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