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

[Mike Bafaro]

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. 
 
Mike  

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Andre
Sent: Tuesday, October 3, 2017 1:51 PM
To: time-nuts@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.



Thanks,

Mike Bafaro WA9ZEO

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[time-nuts] Efratom rubidium oscillator service manual

[Mike Bafaro]

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.  

 

Thanks,

Mike Bafaro WA9ZEO

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[time-nuts] Ball Model PRFS 102

[Mike Bafaro]

Guys,

 

I have a Ball/Efratom Model PRFS 102 that has lost lock as of late.  I got
the  unit used a few years ago and it would acquire lock in about 3 minutes
but now it will not lock at all.

 

The heater is drawing current, at first turn on it takes about 1.4A and in
about ½ hour it draws about 100ma.  So the heater appears to be working but
no lock.

 

The internal oscillator is P/N 100318-003 and I opened it and it has 4 pc
boards connected with a flex board and they are built around the physics
module that in a deep draw case so that I cannot see the lamp.  If I take
the bottom cover off of the module I can see the physics case and I think it
has a hole in one side – is that to view the lamp?  

 

I am told that the lamp fails because the RB is coating the inside of the
glass and it can be revived by heating the lamp with a  heat gun.  Is that
true?  In this model is it easy to get to the lamp or is it more like brain
surgery?

 

There is a similar module on Ebay P/N100318-001  but it has a board on the
side instead of the subD connector and the board on the side may hit the
power input block on the back panel.  I could buy it at $149.

 

I am an electrical engineer that worked at Motorola for 37 years and have
used one of these at Moto a few years ago.

 

I have enough test equipment to do the job…  can you give me some help to
get it running again.

 

Thanks,

Mike

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