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

[Bob kb8tq]

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. ……

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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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