[time-nuts] KS-24361 EFC Error

Bob Camp kb8tq at n1k.org
Tue Aug 11 19:09:05 EDT 2015


From your description it sounds like you have done a very complete analysis of the problem. The
only other thing you *could* do is to run the EFC over 0 to 6V with a power supply and see just
how the OCXO behaves. It would not tell you much more than you know already. It might blow 
something important out on the board.

Here’s effectively what you know:

1) The OCXO is coming up to temperature (it’s close) = not a heater issue
2) The EFC is not shorted (it does tune) 
3) The OCXO has an output and the board recognizes the output = not a shorted output issue
4) The board properly deals with the output that the OCXO has = not a problem elsewhere on the REF-1 board

I’d say it’s time for the big soldering iron and a new OCXO

— OR —

For the very ambitious, start swapping ROM’s and GPS parts from the “dead” REF-1 over to the “live” REF-0. 

I think taking the soldering iron to the OCXO is the better bet.


> On Aug 11, 2015, at 9:44 AM, Matthias Jelen <Matthias.Jelen at gmx.de> wrote:
> Hello Time-Nuts,
> I have a RFTG-U REF-0 / REF-1 pair here which seems to have a problem. The error LED of the REF-1 box stays on forever, and Ulrichs SW reports an EFC Error. After OCXO warmup, the EFC goes doen to it´s lower rail (-100 %) and stays there forever.
> Indeed the 5 MHz Output from the OCXO is abt. 2 Hz of (compared to the 10 MHz Output of the REF-0 which works OK). Tuning voltage to the OCXO is 0V.
> During power up, the tuning voltage is abt. 3.1 V and the OCXO is abt 4 Hz to low. During this time, the DIAG:OSC.EFC:REL? gives me something like 3.085 E+000 - so I guess this is abt. 3% of the tuning voltage.
> Reference voltage output from the OCXO itself is abt. 6.1 V.
> From that I conclude that the tuning voltage range is from 0 to + 6 Volts.
> When the tuning voltage drops from 3 V to 0 V, frequency goes up, but not high enough -2 Hz offset from 5 MHz remain.
> This makes me think that the OCXO has a problem and is not reaching the 5 MHz within it´s tuning range.
> Bevor I heat up the big soldering iron to remove the OCXO, I wanted to ask if anybody else experienced this before and if anybody can confirm that tuning voltage range is indeed 0..6 Volt. If so, replacing the OCXO should cure the problem.
> Regards,
> Matthias
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