[time-nuts] Re: TEMEX LPFRS-01 LPRO repair

[Wilko Bulte]

hi Dave,

Do you get a halfway decent "on frequency" 10 MHz frequency out of the LPFRS? There is only so much capture range, so if the XO is too far off from the nominal frequency the LPFRS will never lock to Rb. I encountered this with an Efratom FRK in which the crystal heater had failed. Fixed the heater: locked ok.

Worth checking I guess.

Wilko

> On 24 Apr 2024, at 16:54, VE7HR via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> I have been having lots of enjoyment out of my TinyPFA. It’s so small, easy to carry and quiet compared to my HP 5370B.
> 
> I am testing it out on my existing pile of frequency sources. One of them is a LPFRS-01. It no longer locks. It locked for a few minutes when I first powered it up.
> 
> Looking in the archives there has been a long standing thread on repairing these devices with several people in the same spot I am in on a used to work LPFRS-01.
> It no longer locks.
> 
> Output from Serial port on mine is
> 8A 1C C3 8A 7C 86 A7 DC
> The 4th column is the VCO control voltage that should be sweeping when unlocked. So that is what the other threads seem to indicate.
> 
> There are some nice teardown pictures of a unit at https://egidy.de/temex_lpfrs_lpro/
> With similar data output.
> 
> I don’t think I have found any service information yet. If I have missed it please point me in the right direction.
> 
> I have not pulled my unit apart bit I am not seeing the trimmer cap that has been speculated to be the fix in the pictures.
> 
> Can anyone shed any light on what to twiddle?
> If I get it fixed I promise to post my results. It’s somewhat puzzling that there is a common question but no answer. Does this mean not one has fixed it or just not one has told us they have.
> 
> Dave
> VE7HR
> Sent from my iPad
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