[time-nuts] Temex LPFRS-01

Azelio Boriani azelio.boriani at screen.it
Thu Apr 12 16:50:47 UTC 2012


Interesting... have to check my LPFRS now: only tested for the lock
indicator when received and then put aside to complete first the
"discipliner".

On Thu, Apr 12, 2012 at 5:00 PM, MailLists <lists at medesign.ro> wrote:

> Well, the saga continues...
> A replacement part (for which a thorough check was specifically asked) has
> arrived. It boasts a "Checked OK" written with a marker pen on the label.
> Promising...
> With high expectations, the necessary connections were made, power
> applied, and after warming up it locks at precisely 9.999,817,1 MHz...
> bummer.
> Sometimes, for (yet) unknown reasons, it unlocks again, and, if the
> frequency adjustment trend is upwards, it locks again at ~10.000.000 MHz.
> The lock signal is active even at higher temperatures - that's quite better
> than the first unit, but after a power cycle the story repeats... mostly
> the wrong frequency comes out, but, on the brighter side, it's locked.
>
>
> On 3/18/2012 10:26 AM, MailLists wrote:
>
>> Yes...
>> Thank you, and the others, for the suggestions for cleaning/reviving the
>> unit, but I can't recommend to my friend to keep a pile of rust (if
>> water damage really is the problem) advertised as an used working item.
>>
>> Regards,
>> bbg
>>
>>
>> On 3/17/2012 4:10 PM, Azelio Boriani wrote:
>>
>>> LPFRS from fluke.l? OK, then open it up and clean it, the LPFRS from
>>> fluke.l suffers from high humidity/water immersion and usually are very
>>> rusty inside. I have received one that was very bad but after cleaning
>>> with
>>> tetrachloroethylene (translated with google) it is working properly,
>>> maybe
>>> it will fail soon but now works. I complained with fluke.l and he
>>> refunded
>>> me without asking to ship back the LPFRS.
>>> TIP: handle with extreme care an opened LPFRS, there is a flexible PCB
>>> that
>>> holds the DB9 connector that can tear in the corners.
>>>
>>> On Sat, Mar 17, 2012 at 10:59 AM, MailLists<lists at medesign.ro> wrote:
>>>
>>>  Hello all,
>>>>
>>>> a friend purchased from the bay a<subj.> in the LPRO configuration.
>>>> After
>>>> some problems encountered during the first power ups, he asked for
>>>> help -
>>>> I'm passing the questions further...
>>>> After about 9 minutes of warm-up from room temperature (22°C) the lock
>>>> signal goes low, but after a short time starts to switch low/high with
>>>> decreasing low periods, until it remains high with short low pulses,
>>>> spaced
>>>> at about 2 seconds. After power-down, and sufficient cooling time, the
>>>> cycle repeats.
>>>> First step was to reapply the thermal interface to the integrated Al
>>>> radiator, which helped a bit, the time during which the unit is locked
>>>> growing slightly.
>>>> Next step was forced cooling, which helped more, so the lock loss
>>>> could be
>>>> attributed with high probability to elevated operating temperatures. The
>>>> temperature of the base plate (integrated Al radiator) at which lock
>>>> gets
>>>> lost is about 40°C, so for a reasonable operation it should not pass
>>>> about
>>>> 36°C, at which the power consumption raises to about 17W. That also
>>>> means
>>>> that for a 1°C/W heat sinking - obtainable with a larger passive HS or
>>>> active cooling - operation above 30°C ambient gets practically
>>>> impossible
>>>> (except refrigeration, Peltier, etc.).
>>>>
>>>> Any further help or suggestions are welcome.
>>>>
>>>> Regards,
>>>> bbg
>>>>
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