[time-nuts] Quieting the HP-113AR Clock/Frequency Divider

Bill Hawkins bill.iaxs at pobox.com
Mon Mar 19 07:05:54 UTC 2018


Here's another experience with a 103 crystal standard with the requisite
100 KC output and a 113 clock. I craved the clock because I'd seen it in
the Smithsonian precision time exhibit.

The 103 was certainly quiet, but the 113 was not, in spite of its heavy
cast aluminum case. The 1 KC stepping motor sings at a frequency that is
most sensitive to the ear. What were they thinking at HP? 

So I built an enclosure in an existing set of shelves. Quarter inch
paneling defined the enclosure, which was lined with thick fiberglass
insulation on all sides. The door was an insulated plywood panel that
had magnetic latches, so you could pull it loose to read the clock. You
could hardly hear it with the door closed.

Both the 103 and 113 were in the enclosure, reducing the temperature
changes typical of Minnesota. An external 28 volt power supply trickle
charged two 12V 7AH batteries with diodes to provide battery power when
the line went out. At the time, the power company was upgrading
underground service, so there were many opportunities to observe
switchover.

I'm sorry to say that I didn't keep detailed records of accuracy. IIRC,
the clock was within a few seconds of WWV at he New Year.

All in all, another fine learning experience. Sold the 103 and 113 after
a few years, and got into telephone GPS with a pair of HP Z3801A and a
16 foot plastic pipe mast for two HP conical antennas. Ended with the
Lucent stuff. Inquiries for recycling Lucent stuff welcome.

Bill Hawkins
bill.iaxs at pobox.com


-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Jeremy
Nichols
Sent: Saturday, March 17, 2018 9:39 PM
To: time-nuts at febo.com
Subject: [time-nuts] Quieting the HP-113AR Clock/Frequency Divider

Those of us with the 1960-vintage HP-113AR/BR Clock/Frequency Divider
know how noisy they are. The mechanical clock movement of my 113AR is
loud enough that I really don't want to be in the same room with it. I
don't know if the clocks are noisy from brand-new or if the mechanism
gets noisier as the various parts wear with age.

Here's how I quieted mine:
. Wrap the outer cabinet of the 113AR in stick-on automotive sound
deadener.
. Put the 113AR in a fully enclosed 4U rack cabinet.
. Stuff insulation into the cabinet so the 113AR is completely
surrounded except for the front panel.

Should anyone be interested, I can provide detailed notes, a shopping
list, and pictures. Total cost was about US$150 and would have been a
lot less if I could have found a used cabinet at the surplus store. 

Jeremy





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