I recently acquired a nice HP-105B, serial prefix 1240A, and like Perry
Sandeen (posted here 10 May 2016) was pleasantly surprised to find a
10811-type oscillator inside in place of the old blue oven. Well, the
oscillator isn't actually labelled "10811" but has a label "Serial No.
3010A62646 / Hewlett Packard / Made in U.S.A. / R11 147K." So, this is
essentially the same oscillator as Perry found in his 105B.
The oscillator works well although the meter reading for the 5 MHz
output is low, about 30 instead of the expected 80 (per the 105B manual
for the 1240A series). The measured output is also low, about 1 Volt
where 1.5 Volt is the expected minimum. Might this be due to the change
from the old 105 crystal oven to the 10811?
What is the received wisdom on replacement of the previously-removed
factory Ni-Cad pack? There are many small 12 Volt batteries available,
two of which would easily fit into the space available and some of which
might not even catch fire! Other options are an external battery+charger
or even a UPS on the AC line. Opinions?
Jeremy / N6WFO
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