[time-nuts] Re: Z3801A questions

[paul swed]

Mahlon I am aware that the big black block that is a DC to DC converter
does fail.
So as you suggest absolutely just replace it with a AC to DC multiple
output unit. Think it was +12 -12 +5. But the schematics and such show what
the voltages are.
The other thing is the input circuit to the unit can also fail. Its all
pretty reasonable to troubleshoot or get rid of if you do not intend to run
on batteries. My Z3801 has never been run on batteries. Though I have 2 X
24 V linear supplies in series for it. Been working fine for 15 years or
more. I am knocking on wood right now.
Regards
Paul
WB8TSL

On Sat, May 20, 2023 at 11:42 AM Bob Camp via time-nuts <
time-nuts at lists.febo.com> wrote:

> Hi
>
> First step would be to look for melted blobs / debris where capacitors
> used to be …..
>
> Bob
>
> > On May 19, 2023, at 9:17 PM, Mahlon Haunschild via time-nuts <
> time-nuts at lists.febo.com> wrote:
> >
> > Hello list.  Just joined and, after reading the list archives, I feel
> that I Am Not Worthy to ask these questions, but here goes.
> >
> > I’ve had a Z3801A just sitting around for years now and, the other day,
> I finally decided to experiment with it a bit.  I already had a 26dB Andrew
> antenna and a Vicor 48V 2.9A power supply for it, so I put the antenna on
> the back of the receiver with some N adapters, wired up a serial cable to
> an ancient ThinkPad running SatStat, placed the whole rig in the back yard,
> and turned everything on.
> >
> > To my astonishment, after placing it into survey mode, four hours later,
> it had completed its sky search and had switched over into position hold,
> with a  TFOM of 3 and a FFOM of 0.  Since all I wanted it for was to use as
> a freq reference, I thought it was good to go.
> >
> > The next day I tried it again.  No go.  The Z3801A acted like it had
> developed an internal power supply short because it was causing the Vicor
> to go into current limiting, with zero volt output.
> >
> > I’ve read the material on 56V vs 48V switching supply startup for these,
> and I will them that next.  Failing that, I’ll troubleshoot the power
> supply.
> >
> > It appears that a long time ago someone reverse-engineered the power
> supply design and published a schematic for it, and Google found it
> somewhere in https://xdevs.com/doc/HP_Agilent_Keysight/ <
> https://xdevs.com/doc/HP_Agilent_Keysight/> but is it on the web
> elsewhere?
> >
> > If all else fails I’m tempted to yank the two DC-DC converters from the
> power supply board and power the whole thing with a suitable AC-DC
> triple-output switcher (specifically, a Nemic Lambda LWT-50H-5FF, which is
> on hand).  Has anyone done this?
> >
> > Lastly, I’m considering trying an Oncore UT+ instead of the VP to get
> its better front-end filtering.  Opinions?
> >
> > Best regards and thanks in advance,
> >
> > Mahlon - N4ZK
> > _______________________________________________
> > time-nuts mailing list -- time-nuts at lists.febo.com
> > To unsubscribe send an email to time-nuts-leave at lists.febo.com
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
> To unsubscribe send an email to time-nuts-leave at lists.febo.com