[time-nuts] HP 115CR Clock Powerup / Documentation
cfharris at erols.com
Fri Dec 23 10:13:14 EST 2016
They are fun little (ha, ha) clocks. There really is no need
to ramp up power. Go for broke, and turn it on.
The only issue you will find in these is a host of wet tantalum
caps that may, or may not be bad. They are on terminal strips,
and are the caps in silver plated metal cans with teflon seals
on the large end. The failure is sulfuric acid leaking out of
the lead on the teflon end.
The other failure issue is the ball bearings on the motor. The
grease is all but certain to be hardened by now. You might be
able to work some light motor oil between the shaft bushing and
The motor will *not* start by itself. You have to open the clock,
press a couple of buttons to start the dividers, and give the
knurled knob on the motor's shaft a spin.
Be careful when setting the odometer display, as it is quite
possible to lock it up. I don't remember how that happens
anymore, but it can.
These clocks are not a lot of fun to live with. They sing along
quite loudly at 1KHz.
Hugh Blemings wrote:
> I've been fortunate enough to acquire a HP 115CR Frequency Divider/Digital Clock -
> it's electromechanical and I suspect built in the mid/late 60s - just slightly older
> than your humble correspondent.
> It's similar though not identical to the 115CR shown here
> I'd like to fire it up - given it's age my thought was to use a current limited 24V
> bench supply and slowly ramp up the voltage the first time - would welcome any
> thoughts on this. I gather from the supporting documentation for the powersupply
> it's rated at drawing ~250mA
> I've been unable to locate a scan of the owners manual or service manual online.
> Have looked at time-nuts archives, leapsecond.com and hparchive to no avail. There
> does appear to be a hardcopy available for purchase - happy to fall back to this if
> necessary, but any pointers welcome.
> My goal ultimately is to have it on display running, synchronised to a GPS disciplied
> 10MHz source :)
> Any thoughts and feedback welcome - this is my first foray into old clocks :)
> Kind Regards,
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