[time-nuts] Z3805 utility, Was: AW: (no subject)

Robert Benward rbenward at verizon.net
Sun May 23 17:51:20 UTC 2010


Bob

Looking at al these pictures, I'm beginning to think I have a Z3801A, not a 05A.  After a few hours, the unit still has 
not locked.  It is possible the antenna is bad. I have a few more that I know are working.  I also took the precaution 
of connecting an antenna before powering up, as  the manual says it will go into an extensive search mode if it can't 
find satellites.

Bob

----- Original Message ----- 
From: "Bob Camp" <lists at rtty.us>
To: "Discussion of precise time and frequency measurement" <time-nuts at febo.com>
Sent: Sunday, May 23, 2010 12:42 PM
Subject: Re: [time-nuts] Z3805 utility, Was: AW: (no subject)


> Hi
>
> The Symmetricom 3805's have an area on the lower board right behind the "control" DB-25. It's very similar to the 
> 3801. There are three rows of holes for 0.025" post connectors. One row pair is labeled RS-232. The other row pair is 
> labeled RS-422. The original intent appears to be to jumper the unit for what ever standard the customer desired. It's 
> not at all clear that the later units are even stuffed for the RS-422 option. There are a number of unstuffed IC 
> locations on the pc board.
>
> Your unit sounds like it's either blown, or running RS-422. I have never seen one of the earlier HP 3805's so I don't 
> really know how much they have in common with the older units. There are indeed USB to RS-422 converters out there 
> that will run on a normal PC.
>
> A good picture of the area in question on the 3801 is shown at:
>
> http://support.ntp.org/bin/view/Support/Z3801AReceiverModifications
>
> The picture you want is the third one down the page, under "RS-232 and PPS modification.
>
> The parts layout on the later 3805's is essentially identical to what's shown in the picture. The LT1180A RS-232 IC is 
> present on the 3805. The chip next to it labeled U5 in the picture is absent. I suspect that is the RS-422 level 
> converter. The labeling of the jumper locations on the 3801 is easier to read in the picture than the equivalent 
> labels are on my 3805.
>
> Since the region obviously dates to the HP era, I'd be quite surprised if it was not pretty similar on the early 
> 3805's.
>
> Bob
>
>
> On May 23, 2010, at 11:30 AM, Robert Benward wrote:
>
>> Ulrich,
>> On pin 2 of the DB9, I get -0.5V, and on pin 3 (TX) I get +2.0V.  Doesn't sound good.  I have a 3805 that has only 
>> the bottom DB25 connector.  The person who sold it to me made a 3 wire cable, DB25 to DB9, with pins 2&3 reversed and 
>> pin 7 grounded.
>>
>> Bob
>>
>>
>> ----- Original Message ----- From: "Ulrich Bangert" <df6jb at ulrich-bangert.de>
>> To: "'Discussion of precise time and frequency measurement'" <time-nuts at febo.com>
>> Sent: Sunday, May 23, 2010 6:29 AM
>> Subject: Re: [time-nuts] Z3805 utility, Was: AW: (no subject)
>>
>>
>>> Bob,
>>>
>>> even without a computer connected the beast should do SOMETHING. In
>>> conjunction with a pc and a running communication it is easier to judge WHAT
>>> it currently does.
>>>
>>> To establish communication first find out what pinning the RS232 connector
>>> has: with the negative cable (black) of a voltmeter connected to Pin 7 of
>>> the RS232 connector check pins 2 & 3 with the positive cable (red) for the
>>> presence of a NEGATIVE voltage of a few Volts. If you can measure a negative
>>> voltage on one of the pins, you have successfully identified the Z3805's
>>> TRANSMIT pin. The other pin of 2/3 is the receive pin.
>>>
>>> Then solder a cable in this way
>>>
>>> Z3805 Transmit pin  -> Pin 2 of pc RS232 port (9 pole D-Sub assumed)
>>> Z3805 Receive pin   -> Pin 3 of pc RS232 port (9 pole D-Sub assumed)
>>> Z3805 Ground (7)    -> Pin 5 of pc RS232 port (9 pole D-Sub assumed)
>>>
>>> Should you have a 25 pin connector for RS232 at your pc then the cable is
>>>
>>> Z3805 Transmit pin  -> Pin 3 of pc RS232 port
>>> Z3805 Receive pin   -> Pin 2 of pc RS232 port
>>> Z3805 Ground (7)    -> Pin 7 of pc RS232 port
>>>
>>> No other connection is needed. With a cable like this start Z38XX and check
>>> that you that you choose the correct Com-Port for communication in the
>>> Parameters window. And yes, I know, being an owner of a Z3805 I should know
>>> exactly but I don't remember the day that I made the cable and I currently
>>> cannot access the back of my Z3805.
>>>
>>> Best regards
>>> Ulrich Bangert
>>>
>>>> -----Ursprungliche Nachricht-----
>>>> Von: time-nuts-bounces at febo.com
>>>> [mailto:time-nuts-bounces at febo.com] Im Auftrag von Robert Benward
>>>> Gesendet: Sonntag, 23. Mai 2010 05:31
>>>> An: Discussion of precise time and frequency measurement
>>>> Betreff: Re: [time-nuts] Z3805 utility, Was: AW: (no subject)
>>>>
>>>>
>>>> Thank you all for these inputs!
>>>>
>>>> Most importantly, the big question is:  Regardless of RS-232
>>>> or 422, will the unit do ANYTHING without communications?
>>>> Do I need a computer to get anything beyond the "power" led?
>>>>
>>>> I bought this at the Dayton convention ham flea market, and
>>>> the guy told me it was already modified for RS-232.  The
>>>> board inside says RS-422 near the connector.  Without the
>>>> other LEDs blinking, I'm worried I bought a dead unit.  I had
>>>> a GPS antenna on it, but it never locked on.  Do I need a
>>>> computer to enable this thing?
>>>>
>>>> Thanks,
>>>> Bob
>>>>
>>>> ----- Original Message ----- From: "Bob Camp" <lists at rtty.us>
>>>> To: "Discussion of precise time and frequency measurement"
>>>> <time-nuts at febo.com>
>>>> Sent: Saturday, May 22, 2010 10:54 PM
>>>> Subject: Re: [time-nuts] Z3805 utility, Was: AW: (no subject)
>>>>
>>>>
>>>> > Hi
>>>> >
>>>> > In this case the RS relates to Radio Shack ......
>>>> >
>>>> > Not a lot of standardization in the RS-232 world. Take a
>>>> look at the
>>>> > slew rate limiting requirements in the original
>>>> > document ...
>>>> >
>>>> > Bob
>>>> >
>>>> > On May 22, 2010, at 9:47 PM, Robert Darlington wrote:
>>>> >
>>>> >> Was there ever a standard?  I always thought the "RS" stood for
>>>> >> Recommended Standard, as in "you *should* do the following" as
>>>> >> compared to "you shall do the following"  I've seen
>>>> inverted TTL talk
>>>> >> to the RS232 port on laptops and I even sometimes use the max233's
>>>> >> (+/- 10 volts instead of 12), but always use the full max232 with
>>>> >> external charge pumps when it's a gadget that needs to
>>>> work everytime
>>>> >> with systems from multiple countries.
>>>> >>
>>>> >> -Bob
>>>> >>
>>>> >> On Sat, May 22, 2010 at 7:21 PM, Didier Juges
>>>> <didier at cox.net> wrote:
>>>> >>> Bruce,
>>>> >>>
>>>> >>> Thanks for the additional information.
>>>> >>>
>>>> >>> +/- 14V is quite unusually low in my experience. I typically use
>>>> >>> +Maxim parts such as the MAX220 series, which is
>>>> >>> specified at +/-25V for no damage on the inputs (some
>>>> parts in that
>>>> >>> series go to +/-30V).
>>>> >>>
>>>> >>> The bottom line is that as I pointed out earlier, there
>>>> is no such
>>>> >>> thing as an RS-232 standard any more.
>>>> >>>
>>>> >>> Didier
>>>> >>>
>>>> >>> ------------------------ Sent from my BlackBerry Wireless thingy
>>>> >>> while I do other things...
>>>> >>>
>>>> >>> -----Original Message-----
>>>> >>> From: Bruce Griffiths <bruce.griffiths at xtra.co.nz>
>>>> >>> Date: Sun, 23 May 2010 10:39:21
>>>> >>> To: Discussion of precise time and frequency
>>>> >>> measurement<time-nuts at febo.com>
>>>> >>> Subject: Re: [time-nuts] Z3805 utility, Was: AW:  (no subject)
>>>> >>>
>>>> >>> Didier Juges wrote:
>>>> >>>> Bill, I think you got it backwards. +/- 12V is typical
>>>> for RS-232,
>>>> >>>> 0/+5V is for RS-422 and RS-485.
>>>> >>>>
>>>> >>>> No RS-232 receiver should be damaged with +/- 12V or
>>>> even +/- 15V
>>>> >>>> because that is their normal operating voltage.
>>>> >>>>
>>>> >>>> Also, RS-422 and RS-485 have something like 25V common mode
>>>> >>>> tolerance (not sure what the actual spec is there,) so that the
>>>> >>>> RS-422 and RS-485 receivers should not be damaged by 15V either.
>>>> >>>> The RS-422 drivers are pretty low impedance, while the RS-232
>>>> >>>> drivers are current limited, so I don't think that connecting an
>>>> >>>> RS-232 driver into an RS-422 driver will damage either.
>>>> >>>>
>>>> >>> Picking one RS485 receiver (ADM1485) at random the
>>>> receiver absolute
>>>> >>> maximum (no damage) input range is -14V to +14V. The
>>>> RS485 receiver
>>>> >>> operating common mode range is -7V to +12V. RS422
>>>> receivers have an
>>>> >>> input operating range of -7V to +7V. The no damage RS422 receiver
>>>> >>> input ratings may be higher.
>>>> >>>> However, most recent (<10 years?) RS-232 receivers will
>>>> work with a
>>>> >>>> 0/+3V or 0/+5V input, conveniently having a threshold a
>>>> few 10's or
>>>> >>>> 100's of mV above ground, even though the original RS-232 spec
>>>> >>>> required receivers that work with as low as +/- 3V, and drivers
>>>> >>>> that deliver +/- 9V minimum. Many commercial systems use +/- 5V
>>>> >>>> drivers for RS-232 (B&B Electronics sells a lot of
>>>> converters with
>>>> >>>> these voltages). This is a deliciously sloppy spec that
>>>> nobody has
>>>> >>>> met in the last 25 years probably, yet works most of the time.
>>>> >>>>
>>>> >>>> The one thing to avoid is to short an RS-422 (or RS-485)
>>>> driver to
>>>> >>>> ground, as that can actually cause damage, maybe not every time,
>>>> >>>> but definitely not recommended. These have relatively
>>>> high current
>>>> >>>> output capability to drive long lines.
>>>> >>>>
>>>> >>>> Didier KO4BB
>>>> >>>>
>>>> >>>>
>>>> >>>>
>>>> >>> Bruce
>>>> >>>> -----Original Message-----
>>>> >>>> From: time-nuts-bounces at febo.com
>>>> >>>> [mailto:time-nuts-bounces at febo.com] On Behalf Of Bill Hawkins
>>>> >>>> Sent: Saturday, May 22, 2010 3:09 PM
>>>> >>>> To: 'Discussion of precise time and frequency measurement'
>>>> >>>> Subject: Re: [time-nuts] Z3805 utility, Was: AW: (no subject)
>>>> >>>>
>>>> >>>> When all else fails, get out the voltmeter.
>>>> >>>>
>>>> >>>> Do you have power to the antenna? Is it the right
>>>> voltage? All the
>>>> >>>> way to the antenna?
>>>> >>>>
>>>> >>>> What volts are on pins 2 or 3 relative to pin 7 in the comm
>>>> >>>> connector?
>>>> >>>>
>>>> >>>> If you see 12 volts, that's RS-422. You may have burned out your
>>>> >>>> computer's serial port.
>>>> >>>>
>>>> >>>> If you see less than 5 volts, that's RS-232 and all
>>>> should be well,
>>>> >>>> unless you see zero volts.
>>>> >>>>
>>>> >>>> I may have the RS-xxx volts somewhat off because my memory isn't
>>>> >>>> what it used to be.
>>>> >>>>
>>>> >>>> The guy you bought it from should be able to help with
>>>> comm basics.
>>>> >>>>
>>>> >>>> Bill Hawkins
>>>> >>>>
>>>> >>>>
>>>> >>>> -----Original Message-----
>>>> >>>> From: time-nuts-bounces at febo.com
>>>> >>>> [mailto:time-nuts-bounces at febo.com] On Behalf Of Robert Benward
>>>> >>>> Sent: Saturday, May 22, 2010 2:08 PM
>>>> >>>> To: Discussion of precise time and frequency measurement
>>>> >>>> Subject: Re: [time-nuts] Z3805 utility, Was: AW: (no subject)
>>>> >>>>
>>>> >>>> Hi All,
>>>> >>>> I hooked everything up and I still get nothing.  I can't seem to
>>>> >>>> establish communications  with the Z3805.  I tried a
>>>> null modem as
>>>> >>>> well, in case the cable (supplied) was wired with the wrong
>>>> >>>> connector gender.  I see a green blinking light inside,
>>>> it he left
>>>> >>>> rear corner of the box.  Everything is warm, but nothing
>>>> else.  Any
>>>> >>>> ideas?
>>>> >>>>
>>>> >>>> Bob
>>>> >>>>
>>>> >>>>
>>>> >>>>
>>>> >>>>
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>>>> >>>>
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>>>> >>>>
>>>> >>>
>>>> >>>
>>>> >>>
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>>>> >>
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>>>> >
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