[time-nuts] The "NAKED" 5065A optical unit

[Bob kb8tq]

Hi

Indeed very cool pictures.

If the lamp is like most gas bulb lights, there is indeed a “strike voltage” required
to get things going (or an RF excitation). There inevitably is some temperature 
dependence as well. A constant current driver might be the better bet.

Bob

> On Feb 20, 2018, at 4:30 AM, Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:
> 
> --------
> In message <AABPJY7PFAJKDQYS at smtpout01.dca.untd.com>, cdelect at juno.com writes:
> 
>> Here is a PIX of the optical unit from a 5065A totally removed from the
>> shield assembly.
> 
> Nice!
> 
>> Left to right:
>> 
>> Lamp assy
>> lamp oven cylinder
>> lamp reflector/convection block/diffuser
>> Rb85 filter cell
> 
> It looks like there is a square filter of some kind
> between the reflector and the filter cell ?
> 
> I've been thinking a little bit more about power for the lamp assembly.
> 
> Since I have the lamp on the bench-supply I am going to plot lamp
> voltage vs. photo-I because it looks like a threshold rather than
> a linear relationship.
> 
> If that is the case, I think it will make sense to give the lamp
> its own adjustable voltage regulator (LM317), so the power can be
> reduced to what is optimal/necessary without having to take the
> lamp apart and change a resistor.
> 
> A 1R resistor between the 22-30V supply and the LM317 will make it
> easy to monitor lamp current, and a 300mA short-circuit protection
> is a nice bonus.
> 
> If need be, the regulator could start out at 20V and drop to something
> lower in a matter of minutes.
> 
> Actually, now that I think about it, I should try to measure if it
> is gives better stability if I drive the lamp with constant current,
> constant power, constant voltage or constant photo-I...
> 
> -- 
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe    
> Never attribute to malice what can adequately be explained by incompetence.
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