[time-nuts] Z3801 misbehaving

paul swed paulswedb at gmail.com
Tue Jan 26 12:56:33 UTC 2016

The 3801s are getting very old at this point. I know mine has started to
show a loss of lock occasionally on the oscillator. Intermittent problems
are very tough.
What jumps out to me is the 27 volts. That seems low as I recall. I run at
48 V. I understand there were several models made so what I mention may not
be correct.
The other thing is there is a small regulator on the power board.
I know on my unit one of the regulated outputs on the switcher failed and I
simply replaced it with another small block switcher. Though as you mention
your voltages appears fine.

On Mon, Jan 25, 2016 at 8:54 PM, John Green <wpxs472 at gmail.com> wrote:

> After running continuously for about 3 years at work, I stored my Z3801 for
> a little over a year. I recently took it out of storage and when I hooked
> it up, all I get is a power on light. The front panel LEDs light in
> sequence and the 6 inside blink red once and then the last one blinks
> continuously as always. Thing is, it never locks on GPS. I even left it on
> over night. When run on 27 volts, it starts out at about 1.1 amps, then
> after about 10 minutes, goes up to 1.26 amps. Then, after about 30 more
> minutes, it settles down to .88 amps and stays there. The OCXO gets warm. I
> haven't checked for 10 MHz out, but I am pretty sure it is there. I hooked
> it up to my netbook but I get no response from it at all. I am using one of
> those USB to serial devices and it used to work. I am looking for a PC with
> a real serial port to try. I know the antenna is good. It works with one of
> those Symmetricom GPSDO cards.  Having heard about the evils of tantalum
> capacitors for years, I replaced them all except for those on the GPS
> receiver board itself. All the test points that call out a voltage read
> correctly. I'm thinking of trying a new GPS board next. I have had this
> thing a long time and it has always just worked. Any ideas what the problem
> is?
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