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

Bob Camp lists at rtty.us
Sun May 23 16:42:37 UTC 2010


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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