[time-nuts] EFRATOM FRK Lamp Voltage

Ulrich Bangert df6jb at ulrich-bangert.de
Thu Aug 10 10:19:18 EDT 2006


Joe,

> locks up quickly enough and works fine as far as I can see. I 
> realise that the lamp voltage is only the output voltage of 
> the first op-amp after the photo-diode and may not be a 
> reliable indication of its true health.

the lamp voltage may be taken as the lamp's health indicator if every
other parameter that has an influence on the lamp voltage has been
checked to be ok. The two most prominent factors for the lamp voltage
except its own health are

a) the lamp's temperature

and

b) the lamp's excitation frequency.

Both of them have an impact on the quality of the plasma excitation
within the lamp. If two different lamps show a similar behaviour in your
FRK-L i would bet on one of these parameters being wrong. The
maintainance manual has some pages on how to measure and set these
parameters. However, is a bit tricky because it involves removing the
base plate (where the heat sink is mounted at). The base plate holds a
TO220 transistor as a heating element at its inner side that is soldered
with VERY short wires to a pcb, so it is mechanically a adventure to
handle the base plate. Therefore i also suggest you keep it running
until severe problems occure like lockouts after warmup a.s.o.

If you need the maintainance manual i can send it as a personal email.
It is abt. 5 MB.

Regards

Ulrich Bangert 


> -----Ursprüngliche Nachricht-----
> Von: time-nuts-bounces at febo.com 
> [mailto:time-nuts-bounces at febo.com] Im Auftrag von Joe McElvenney
> Gesendet: Mittwoch, 9. August 2006 20:54
> An: time-nuts at febo.com
> Betreff: [time-nuts] EFRATOM FRK Lamp Voltage
> 
> 
> Hi,
> 
>    A few years back I obtained a Racal-Dana rubidium standard 
> with a EFRATOM FRK-L fitted. I was concerned that the 
> indicated lamp voltage was about 5.5V where the book says it 
> should be between 6 and 12V. Subsequently I obtained another 
> lamp from a surplus source hoping that the voltage would move 
> upscale when changed. Unfortunately it didn't and has stayed 
> around 5V, slightly lower than the original. I can't put the 
> old one back because I cracked the glass when prizing it out 
> of the sealing compound.
> 
>    So, was I seen off or is this typical of the voltage 
> spread likely to be encountered? I must say that the unit 
> locks up quickly enough and works fine as far as I can see. I 
> realise that the lamp voltage is only the output voltage of 
> the first op-amp after the photo-diode and may not be a 
> reliable indication of its true health.
> 
>    Anyone know of a cheap source of spare lamps?
> 
> 
>    TIA - Joe
> 
> 
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