[time-nuts] nortel NTGS50AA embarrassing moment OCXO EFC Pin open circuit

Mark C. Stephens marks at non-stop.com.au
Sat Sep 7 14:17:32 UTC 2013


Just in case someone ends up in the same boat with the EFC control voltage not reaching the EFC pin on the OCXO.
Due to the plated through hole being accidently but inadvertently removed, for example <red face>

You can pick off the EFC control voltage from TP23 next to the great big 4u7 NP SM cap on the other side of the oscillator package than the silk screen for the SMA/B connectors.
Use some wire wrap wire from TP23 to the pin and you are set.
Shame it happened but on the plus side, I got to reverse engineer the EFC D/A circuitry, well at least garner some information on its mechanics.

It is of interest that the OCXO reference voltage out never seems to be used on many of these designs (HP Z3816A, Trimble NTGxx)
This is the middle pin between RF out and EFC.  If I am wrong about this, please pipe up as I am quite curious?


--marki
-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of Mark C. Stephens
Sent: Friday, 6 September 2013 11:21 PM
To: time-nuts at febo.com
Subject: [time-nuts] nortel NTGS50AA embarrassing moment OCXO EFC Pin open circuit

I got sent a duff NTGS50AA with a crook Trimble 49422C oscillator module.
Not from Bob, he always checks his stuff, I have my vague suspicion this was sold as "untested" when the seller knew it was a dud..

Anyway, we are rearranging the workshop and I couldn't get to the Weller desolder station.
All I had on hand was an Aoyue or however it is spelt.
It is some such oem'ed or cheap copy of a hakko desolder pistol.

People warned me, it won't get hot enough for what you are trying to do, but did I listen?
Well, after pulling 3 plated through holes out, I wished I had.

I fixed the ground and 10Mhz but I can't find the EFC.
If someone has an NTGS50AA handy,
please trace where the EFC pin on the ocxo goes to where (pin on IC, buffer transistor etc)?


Cheers :)
--marki
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