[time-nuts] problem with Efratom FRS-C from eBay

Scott Mace smace at intt.net
Sat Oct 18 01:09:05 UTC 2008


I have a FRS-A which is very similar to your unit, but with a LPRO compatible
pin-out.  This came out of a Lucent RFTG box.  It would take a long time to power
up, and I found that the power supply was no good.  I removed the unit and kept
it on a piece of the chassis as a heatsink and used a new 24v switcher.
This unit still takes longer than the 10min to lock, but once it locks it's solid.
The lock indication goes low when locked, high when unlocked.  It has a strong 10mhz
TTL output.  You should attach some sort of heatsink to the baseplate.  The FRS-A
runs hotter than any of the LPRO units I have.  I've had good luck with the
Datum labeled LPRO-101 units.  What are you using the measure the frequency?
Sounds like your unit is locking if the BITE is low.  The usual thing that
kills these units isn't the lamp itself but noise from some other source in
the physics package.

I've purchased from this seller several times before and he replaced a bad
LPRO unit (powered up and locked for 1 hour then unlocked and never locked
again).  Usually, it is not practical to repair these units as most of the parts
cannot be swapped from unit to unit without changing some undocumented adjustments.

	Scott


Robert Darlington wrote:
> Hello all,
> 
> My FRS-C showed up today.  I carefully wired it up and powered it on.  I got
> a nearly 10MHz signal out.  The frequency counter is dancing around a bit
> and I get a 0.02 V on the lock indicator line after about an hour warm up.
> Specs show this should happen in under 10 minutes and it looks like it is
> not locking.   Dead unit?
> 
> I obtained it from this ad:
> http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=290262243079
> 
> The unit that I received does not show TTL after the frequency and the scope
> output looks like a cross between a sinewave and a ringing square wave.  I
> have about 13 feet of RG174 between the FRS and the measurement equipment so
> who knows.   This is the "*Rubidium and GPS DO From
> China<http://stores.ebay.com/Rubidium-and-GPS-DO-From-China>"
> *eBay store, which I thought was pretty reputable so I want to make sure I'm
> not doing anything wrong before I contact the seller, PayPal, etc.*  *There
> was also a big white sticker covering the whole top of the unit.  I had to
> remove it to verify the pinouts and the model information.  Hoepfully that
> didn't void my warranty on the $100 paperweight.  Should I let it sit
> overnight?  Any suggestions would greatly be appreciated.
> 
> Thanks,
> Bob, N3XKB
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