[time-nuts] Re: HP 115BR Clock 60 Hz output option

[John Vendely]

Hi Chris,

You're definitely on to something here, something I completely failed to 
notice--that second photocell, V102, which is "NC" in the standard 
product, but clearly used in the 60 cps output option, according to the 
parts list! Â  In the 115BR days, some form of triggered divider would be 
have been necessary to to provide the large division ratio needed to get 
down to 60 cps. And, as it happens, the 1 kc is derived from a 
regenerative divider, which naturally includes a frequency tripler 
providing 3 kc as part of its conversion scheme.  Buffer the 3 kc output 
from the 1 kc regen. divider and use the second photocell in conjunction 
with a spinning aperture disc to generate an optical gate (as was done 
to generate the 1PPS) to select every 50th pulse of 3 kc .   Something 
along these lines, anyway.

I shall look more closely at the 115BR mechanics and electronics, and 
peruse the parts lists and see if I can ferret out the details.

Many thanks for everyone's interesting suggestions...

73,

John K9WT

On 3/7/2023 1:48 PM, Chris Caudle via time-nuts wrote:
> On Tue, March 7, 2023 10:29 am, John Vendely via time-nuts wrote:
>> If nothing else, I'm curious to see how HP
>> accomplished the 60 cycle output option.
> That would be interesting.
> The service manual is available at ko4bb.com and has a note that the aux
> output is 0.25V RMS minimum (so 0.06V is definitely below spec), and the
> parts list has V102 as a photocell used for the 60 cps option only.
>
> I am not familiar with any divider circuit which uses a photocell, but
> perhaps that will ring a bell with someone else.
>