[time-nuts] HP 58501A reference clocks

[Steve D]

This is a followup on the 58501A. I have the unit working now. The location
was fixed in the units EEPROM to coordinates 37.3586547°, -079.1746364°.
Zooming into those coordinates with google earth gives you a pretty good
idea of where its antenna was mounted in the 90's. Using Tac32 I was able
to see that it would program the GPS receiver with that position at power
on and then put it into position hold mode. The solution was to simply
remove the EEPROM altogether. It had some other data in it but the unit
appears to work great without it installed. If any data in the EEPROM is
altered it ignores the whole thing so it is checksum protected. The alarm
LED never comes on that I can tell but the GPS lock LED works just fine. I
have ordered a slightly more modern/sensitive GPS receiver for the unit as
the one it has now is pretty terrible. The current GPS is old enough it
uses true RS232 for communication. The 58501A has jumpers to select between
RS232 and TTL for the GPS data though so it should be an easy to swap to
something newer. I am testing its hold over performance which looks to be
excellent thanks to the OCXO installed.
I have many uses for the 10 MHz out and may have a use for the 19.2 MHz out
but have no idea what I can use the 9.6 kHz or 100 Hz outputs for. There is
also 1 PPS on the DB25 connector. No further useful SCPI commands have been
found.

I still think it is pretty cool to have a one off prototype from HP(that
also works!).

Steve VE7FM

On Sat, Mar 26, 2016 at 6:35 PM, Bob Camp <kb8tq at n1k.org> wrote:

> Hi
>
> I wold not be at all surprised if it has a previous location surveyed into
> it’s little
> brain. As long as it still thinks it’s in Virginia (or wherever) it’s not
> going to
> lock up in it’s new home.
>
> Depending where it came from, it might be a lab unit for initial design
> checkout.
> If HP shipped a unit like that to a customer, it would be the first
> example I’ve seen.
> Since there are a *lot* of things I have not seen … that may not mean much.
>
> Bob
>
> > On Mar 26, 2016, at 7:13 PM, Steve D <kls at ve7fm.com> wrote:
> >
> > Hi group,
> >
> > I recently purchased an HP 58XXXA or 58501A precision reference clock
> unit.
> > The unit is clearly a prototype made by HP for Ericsson GE. The front
> label
> > actually says 58XXXA. The serial number of the unit is EGE001P. It has a
> > GPS antenna in and 10 MHz, 19.2 MHz, 9600 kHz and a 600/300/100 Hz
> outputs.
> > Inside is has a main board with part # 58501-60001, a 10 MHz OCXO part #
> > 05071-60219, a Motorola GPS part # 84D43215M02, a hand built board which
> > generates (likely phase locked) 19.2 MHz from the 10 MHz, a hand built
> > board to hold the three front mounted LED's and a third party power
> supply.
> >
> > At power up the front panel power LED comes on and a second later the GPS
> > and ALARM LED's toggle on/off in sequence. The main board LED's also all
> > toggle and then one of them flashes once per second. I can communicate
> with
> > the unit via SCPI using 9600/8/N/1 RS232 data.  I was able to verify the
> > GPS does receive a signal as the time is correct and the date updates but
> > is 1024 weeks behind(GPS rollover bug). However the "GPS LOCK" and
> "ALARM"
> > LED's never do anything. The 10 MHz out the back does travel between
> > 9,999,997 and 10,000,003 Hz which follows the EFC test point voltage that
> > goes between -5 and +5 volts. I have found very few SCPI commands that
> > work. At this point they are:
> >
> > *IDN? which gives: HEWLETT-PACKARD,58501A,0,Fiji_EGE
> > *CLS
> > *TST? which gives 1 (possibly indicating a rom error)
> > PTIME:DATE?
> > PTIME:TIME?
> > SYSTEM:ERROR?
> >
> > I have pulled the four firmware roms and reseated them as well as the
> > Xilinx chip, it made no difference. So the question is, did it ever work
> or
> > has something failed?
> >
> > I find it to be a fascinating piece of equipment and think the hand built
> > boards are super cool to see, but lets face it, it would be more fun if
> it
> > worked.
> >
> > I have posted pictures and a firmware dump on the eevblog forum here:
> >
> http://www.eevblog.com/forum/testgear/prototype-hpagilent-gps-based-refererence-clocks-generator/
> >
> > I'm coming to this group to see if anyone has any ideas or knowledge of
> the
> > unit.
> >
> > thank you!
> >
> > Steve VE7FM
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