[time-nuts] Re: Internal power supply for Z3801A

[Lon Cottingham]

The power supply that I need is the 48v (sorry for calling it 50v I
was an Airline Pilot,
not an engine) supply that  bolts to the motherboard with Torx T-15
bolts just above
Motorola Oncore GPS receiver board.  I will certainly take a 24v
model, if I have to,  but
prefer the 48v model because this particular Z3801A chassis already
has a 48v power
supply built inside there rear of the chassis to power the original,
bolt down,  Z3801A
48v power supply.

This may sound confusing.  Some explanation is in order.  About 20
years ago I bought
25 Z3801A's from a surplus dealer in Dallas.  These units were just as
they came out of
the early cell towers, basically useless to Hams.  These units all
required 48v to run them, had
no display, other than some LED's, and were good for nothing except an
excellent time base
without being hooked to a computer.  I did a little machining to the
chassis and added a
transformer and a few parts to supply the 48v these Z3801A required.
Also added a 3 wire AC
line plug.  Also added Dave Robinson G4FRE / WW2R clock with a nice
bezel from Digikey.
The clock made the unit desirable and they sold like "Hot Cakes".
Unfortunately, when I went
back to the dealer in Dallas for more Z3801A's, the price had gone up
about 4 times from what  I had
originally paid.  It seems that Hams all over the country had about
the same idea that I had.  That
ended the project for me.

Through the years I got a few of these units back for service for
various reasons.  Mostly it was
just for lack of understanding.  Now, twenty years later, rather than
just throwing the parts units out,
I decided to see what I can make out of them.  If I can find the 48v
power supplies I can easily put
one complete unit together, and possibly two.  Thus my post.


73 de Lon, K5JV
K5jv@ kingwoodcable.com
281-795-1335
.

On Fri, May 6, 2022 at 3:31 PM Lon Cottingham <lonk5jv at gmail.com> wrote:
>
> On Fri, May 6, 2022 at 3:22 PM ed breya <eb at telight.com> wrote:
> >
> > I'm a little confused now about what power supply is at issue. The
> > normal PS board in the Z3801A mounts on top of the main board, and
> > provides +/- 15V and +5V to it, to run everything. The PS board also
> > includes the outer oven control, run from a separate 5V DC-DC converter.
> > The two DC-DC converters and a bunch of support circuitry are rigged to
> > run around 24V or 48V nominal, depending on the sub-model.
> >
> > Is this the board that's missing? If so, now I understand why you're
> > looking for a whole new one. I was picturing fixing one that's crapped out.
> >
> > I wouldn't be too picky about getting a 48V one versus 24V one - it's
> > better than nothing, and it's quite easy to change the external PS to
> > 24V. Go with whichever one you can find.
> >
> > If you can't find anything at all, and build an alternate system, you'll
> > need to replicate the outer oven control, besides supplying the main
> > board power.
> >
> > Ed
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