Ed,

I think my 48V golf car battery bank is stiff enough for this :)

Seriously, that is what I always intended to try first.  Fed through a suitable fuse/circuit breaker, of course.  Will give it a go and report back later.

Best regards

Mahlon -N4ZK

Hi

Each time I’ve had a Z3801 fail, a fuse in the front end (ahead of the internal supplies) has been the issue.
Replace that fuse and they go back to normal function for a number of years. Obviously, a blown fuse is
open circuit and we’re looking at a short in this case.

It does bring up the question: What about that fuse?

1. The cap you “lost” is ahead of the fuse. Not sure there are many in that category …

2. The fuse is defective.

3. The fuse was replaced with a short at some earlier repair point.

4. It’s also possible that there multiple versions of the 3801 and some do and others don’t have fuses.

Something more to consider.

Bob

Well, as expected, when connected across my 48VDC infinite current source (e.g. golf car battery) the Z3801A booted right up.

Now all I need is a 48VDC 5A unregulated power supply.  Decades ago, these things were a dime a dozen.  Now they cost hundreds of dollars.

Or maybe a suitable step-start or ICR between the Vicor SMPS and the Z3801A.  After all, the Z3801A only draws roughly 500 mA, steady-state, while the Vicor can source 2.9A.  Plenty of room for that sort of thing.

Thanks for your support.

Best regards

Mahlon - N4ZK

Hi

Now that it has started up again, I’d go back and try the switcher.
You might have simply cleared a short somewhere.

Bob

Not cheap, but not particularly expensive, $50 gets you a new 48V / 5A supply:
https://www.mpja.com/48-Volt-Power-Supply-5A-240W-Hengfu/productinfo/18437+PS/

For a few dollars less, series up a pair of 24V / 6.5A supplies:
https://www.mpja.com/24-Volt-Power-Supply-65A-150W-Switching/productinfo/33470+PS/

Bob LaJeunesse

FWIW, we have four *Z3805As *(they are different, but not too different
from the Z3801A design) and we run each one from a dedicated Meanwell
GS60A24-P1J 24V, 2.5A tabletop switching power supply (with an XLR
connector in place of whatever was the original dc plug). No issues.

And also FWIW, we recently replaced the Motorola Oncore receiver inside one
of them (that had died) with one of synergy-gps https://synergy-gps.com/'
16U54523G-B1 replacement GNSS receiver and it works great; it locks much
more quickly than before. Am now waiting for another four 16U54523G-B1
units so that we can complete the updates.

--Andrew

Andrew E. Kalman, Ph.D.

On Fri, May 26, 2023 at 6:23 PM Mahlon Haunschild via time-nuts <
time-nuts@lists.febo.com> wrote:

A traditional soft start circuit you could try would be to use a series
resistor and a 48V relay. 20 ohms would limit the current to the max of
your 2.9A supply. Connect the relay coil between the load side of the
resistor and ground. Connect the relay contacts so they short the resistor
when the relay is engaged. At startup, the load acts like a very low
resistance and the relay does not pull in right away. As the load
current drops, the voltage on the relay coil increases until it pulls in,
connecting the supply directly to the load. Hopefully the supply can handle
this smaller surge.

You may have to experiment with the resistor value. A larger resistor would
reduce the surge but it must be small enough so that the relay eventually
pulls in and the load starts up properly. Also consider the power rating of
the resistor, and whether you need a slow blow fuse to protect it in case
the load is shorted.

On Sun, May 28, 2023 at 4:44 PM Robert LaJeunesse via time-nuts <
time-nuts@lists.febo.com> wrote:

--

--Jim Harman

Thanks, but I already thought of that.  Nope.  Still inop.

I’ve done relay-switched step-starts in the past for other applications, I’ll probably go that route if I can’t get an ICL to work.

Thanks all.

Mahlon - N4ZK

My inrush current limiter assortment arrived yesterday, so today I tried a 20 ohm 9 amp ICL in series with the Z3801A positive supply line. Success!  The receiver starts reliably and continues to run, with only a one volt drop across the ICL.

The ICL is a very simple solution to this problem, and I’m surprised that it hasn’t been thought of before (unless of course I just didn’t run across it).

I think the permanent solution will be to internally-mount a pair of 10 ohm 9 amp ICLs in series; the single 20 ohm part gets quite warm, and I prefer to spread the heat across more than one of these ICLs.

There’s probably a better part choice than what I am using, by the way.  I chose the part because I knew that I wanted to limit the load on the Vicor power supply to 3 amps (20 ohms is close enough, it seems).

Will report back once the unit warms up (and the current drops to steady-state) if there are any further issues.  No news will be good news, in this case.

Best regards

Mahlon - N4ZK