[time-nuts] time-nuts Digest, Vol 159, Issue 3

Mike Bafaro m.bafaro at comcast.net
Thu Oct 5 14:50:39 UTC 2017

The unit I have is locking intermittently and I see a waveform at TP1 on the servo board that is a clipped sine wave when it is locked. The waveform at TP1 when unlocked is about .2V p-p.  I am concerned that the clipping on the bottom of the waveform is a problem with the bias on the sync detector stage.  I am just guessing. When the unit is locked the lamp voltage is 10.0V and the crystal voltage is 6.5V.  This seems to be OK. But in about 10 minutes it breaks lock and it may or may not lock again. But I had to add a .01uf at the lamp voltage pin of the main connector to get it to lock at all.  Without the .01uf cap it would break lock as soon as  I touched the DVM probe to the lamp pin on the main connector.  I was going to enclose the waveform I took but I guess it is too big a file.   Also I noticed that the output of middle gain stage in the lamp photo diode amplifier is biased at 1.6V which I think should be at about 5V.  There must be an issue with the LM324 or the bypass cap.  The resistor from +5V to the + input measures OK. 

-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Andre
Sent: Tuesday, October 3, 2017 1:51 PM
To: time-nuts at febo.com
Subject: Re: [time-nuts] time-nuts Digest, Vol 159, Issue 3

Whats up with it? There are related manuals for these around and one common problem is bad 10K resistor on the lamp board.
Apparently the heat does them in over time.

Interestingly a lot of "military surplus" units can in fact be probed using a random generator over serial port to see what comes back.
Takes a while but can yield results as commands although undocumented can sometimes be brute forced by comparing with known similar units.

Does anyone know where I can get a service manual for an EFRATOM part number
100318-001 or -003.  This is used in the EFRATOM model PRFS102.  The manual for the base model may have the data on the oscillator.


Mike Bafaro WA9ZEO

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