[time-nuts] Temex LPFRS-01

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That would be the tougher part, as, with highest probability, the 
external analog adjustment is first AD converted in the MPU (AIN4) 
summed with the internally stored fine adjustment value, and then 
applied to the C-Field correction, through an external DAC8800.
As both conversions are 8 bit, the obtained resolution of 1E-11 is 
insufficient to discipline the unit with enough accuracy, it was just 
meant to adjust the working frequency.

In the last day of the easter holidays I opened one up, and now I'm 
trying to grasp the inner workings... time allowing.


On 4/12/2012 7:50 PM, Azelio Boriani wrote:
> 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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