[time-nuts] My stubborn Z3801A
Richard W. Solomon
w1ksz at earthlink.net
Mon Jun 14 00:43:58 UTC 2010
If you remove those "zero ohm" resistors, you need other jumpers
to make it work as an RS-232.
When I did mine, I stuck in two strips of "headers" and used those
HD jumpers to select RS-232 or RS-422.
Check out this site:
73, Dick, W1KSZ
>From: Robert Benward <rbenward at verizon.net>
>Sent: Jun 13, 2010 8:01 PM
>To: time-nuts <time-nuts at febo.com>
>Subject: [time-nuts] My stubborn Z3801A
>An update to my Z3801A saga.
>Summary: As you know, I purchased this Z3801A at the Dayton Hamfest. The
>person who sold it to me said it was modified for RS-232. I powered the
>unit up and the only thing it ever did was go into the holdover mode. Tried
>hooking RS-232, but got no response. Did some reading and found the little
>green blinking light was a good thing, all the others indicated a failure in
>ram, rom, etc. Boot was good if all the front panel lights went on in
>Update: Took the unit apart to do some serious trouble shooting. Found the
>signals (logic side) on the RS-232 did not go all the way to ground. Subbed
>in another RS-232 transceiver, still no luck. Found another note on the
>internet about removing the 5 little zero ohm resistors on the bottom to do
>the RS-232 conversion. Looked on the bottom and they were still there!!! I
>removed them and the signals now went all the way to ground and appeared to
>be normal. Tried various programs to link up (GPS.EXE, SatStat, RS-232
>comm). Saw the commands going in, and I did see a response from the Z3801A,
>but the computer could not read the response. Since I did see a response
>from the Z3801A on the scope, I figured it was receiving commands. I hooked
>up an antenna and sent a survey command. Apparently if the GPS is moved (I
>don't know how much) the Z3801A needs to do a survey otherwise it won't
>lock. I went shopping, and came back about 2 hours later, and low and
>behold, a GPS LOCK!!!
>Still to go: The RS-232 signals look fine going into the cable, +/-5V, any
>ideas why the computer won't read it? Am I missing something? I tried two
>different ports in case I screwed one up one of the ports, but no luck.
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