[time-nuts] Z3801A/58503A Help

Jerry jreed123 at cox.net
Sat Dec 11 15:45:32 UTC 2010


I recently purchased a Z3801A/58503A off of E-bay from Yixunhk in Hong
Kong.  The unit arrived quickly and was complete with antenna, power
supply and some software.  It is a nice kooking package with an HP
case much like the HP3805.  The first problem was that the case was
marked as requiring a 38-60 volt power supply which seems to be the
common power supply for the Z3801A.  The power supply that came with
the unit was a 24 volt power supply.  After a lot a research and help
from several members of time-nuts I deduced that the vendor had
changed out the power board in the unit and that it did in face run on
24 volts.  In trouble shooting the unit I found several loose screws
which were likely affecting the operation of the unit.  After I got it
going I noticed that the EFC voltage plots were jumping all over the
place and about every 24 hours it would drop out of lock because the
EFC could no longer keep the oscillator in spec.  More trouble
shooting revealed that the power to the outer oven was never coming
on.  There is an output on pin 10 of the cpu that turns on the outer
oven and this output was never going active.  Some additional research
found that others have had a like problem and that by pulling up the
input to the outer oven circuitry they were able to get the cpu to
reset and work normally.  When I pulled up the input to the oven it
worked normally but the cpu would never reset.  I have had numerous
E-mail with Yixunhk and he has been of no help.  It will cost $200 to
return the unit to Hong Kong.  If anyone has any suggestions I would
like to hear them.  In the meantime based on my experience I would
think twice or more about doing business with Yixunhk.  He advertised
the unit as fully functional and claims that it was fully tested.
This problem was not caused by shipping damage and any tech with
experience on this type of equipment should have recognized the
problem.  Sorry about the long ramble but I thought my experience
might help someone else.
Jerry



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