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

[Jeremy Nichols]

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.