[time-nuts] HP105B HP 105B 1 amp fuse blowing

[Dana Whitlow]

I once read that Supercapacitors come up short in handling really short
spikes,
and that this is not due to physical inductance arising from the
structure.  Rather,
the issue was of a subtle (to me) electrochemical nature.

Can anyone either confirm or refute this?  Inquiring minds want to know.

Dana

On Fri, Oct 11, 2019 at 2:01 PM Bob kb8tq <kb8tq at n1k.org> wrote:

> Hi
>
> Indeed, the unit seems to work fine without batteries.
>
> -------
>
> If filtering and short duration spikes are the concern, one could
> replace the batteries with super capacitors. One would *hope* they
> are a bit less likely to create problems. ……
>
> -----
>
> While it is a good idea to keep OCXO’s on power, a half hour or
> couple hour outage is not that big a deal. They will settle back down
> pretty fast after that sort of interruption. Unless the rest of the lab is
> on backup power, there may not be a major need for the 105 to stay
> up and running ….
>
> Bob
>
> > On Oct 11, 2019, at 11:59 AM, Jeremy Nichols <jn6wfo at gmail.com> wrote:
> >
> > The 105A was built without a battery. The 105B has a battery and charger.
> >
> > I have a 105B that had the failed battery removed before I bought it. It
> > works fine. I have it on a UPS; it survived our just-finished NorCal
> power
> > shutdown just fine.
> >
> > Jeremy
> >
> >
> > On Fri, Oct 11, 2019 at 7:01 AM Scott McGrath <scmcgrath at gmail.com>
> wrote:
> >
> >> As one who owns a 105 i had the battery properly rebuilt and basically
> >> have it on low rate charge and periodically discharge the battery
> >>
> >> When rebuilding a 105 battery it’s important to replicate its
> >> characteristics
> >>
> >> Remember HP also intended I believe that the battery would also serve
> as a
> >> filter for the power supply.   As I dont recall any version of the 105
> >> without a battery.
> >>
> >>
> >>
> >> On Oct 10, 2019, at 4:50 PM, Taka Kamiya via time-nuts <
> >> time-nuts at lists.febo.com> wrote:
> >>
> >> The fact that 25V supply is dropping to 23.4V shows it is drawing far
> more
> >> current than it is rated.  I am assuming this is a regulated power
> supply.
> >> Does the power brick actually shuts down at 500mA or does it let the the
> >> voltage drop and try to supply what it can?  Maybe one or more Nicad
> has an
> >> internal short?  That will cause and over-voltage situation per battery
> and
> >> thus over-current.  I've recently seen a brick power supply go into
> >> oscillation and produce 3x rated voltage when too much current was
> drawn.
> >> (and blew the circuit)
> >>
> >> Also, different batteries has different charging rates.  As far as 105B
> >> document goes, it says 24V 0.5Amp supply but that is for default
> >> configuration. Designed charge rate is 390mA (page 3-4) and is current
> >> controlled by A5Q3.
> >>
> >> I would actually measure how much current is drawn there.  Since the
> fuse
> >> is already blown, just put an am-meter across the fuse and see....
> >>
> >> ---------------------------------------
> >> (Mr.) Taka Kamiya
> >> KB4EMF / ex JF2DKG
> >>
> >>
> >>   On Thursday, October 10, 2019, 4:00:41 PM EDT, Roy Thistle <
> >> roy.thistle at mail.utoronto.ca> wrote:
> >>
> >> Hi All:
> >> A 105B (quartz oscillator) is blowing the 1A fuse, after it is on about
> 1
> >> hour.
> >> The fuse appears to have just melted (not a black mark as the result of
> a
> >> flash, in the case of a high current short.)… just looks like the fuse
> wire
> >> (inside the glass capsule) melted into some little blobs, for about 1/4
> >> the fuse length, near the middle. It wasn't a fast-blo or slow-blo
> fuse...
> >> just the normal kind.
> >> I think the unit is drawing just a little too much current, as the
> result
> >> of the batteries needing charging (I had the fast charge option on when
> the
> >> fuse blew.) And so, the fuse heated up, and finally melted. Not sure why
> >> the batteries were not charging normally... but 20.1 volts is what I
> >> measured across the pack, initially, and 23.4 V after about 45 min of
> >> charging.
> >> I am charging the batters, from a power cube, at 510 ma, and dropping
> >> (cube gives 25V, 500mA max)… the batteries are 20 C size NiCads, wired
> in
> >> series... that of course is a retrofit.
> >> I don't want to put another fuse in, and blow that too, without some
> >> reasonable explanation of why the first one failed!
> >> Please, any comments, or hints/suggestions... much appreciated.
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> >>
> > --
> > Jeremy Nichols
> > Sent from my iPad 6.
> > _______________________________________________
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