[time-nuts] Racal 1992

[Ed Palmer]

John Green wrote:
> Ed Palmer wrote:Which timebase does yours have?  I've got option 4E (similar
> to 4B).
> Although the timebase appears to be stable, I've noticed that the
> counter drifts about 5e-9 during warmup, even when the oscillator has
> been on standby for many days.  It takes a couple of hours to settle
> down.  Does yours do anything similar?
>
>
>
> Ed, Exactly which reference I have seems to be something of a mystery. The
> part number on it is 454879. The part number listed in my manual is 404386.
> My manual makes no reference to optional timebases. The manual I downloaded
> does but doesn't list the part number I have as a choice. Though it is
> ovenized, I don't believe it is the best high stability type. It does look
> pretty good in general terms. Retrace is important to me and it seems pretty
> good in this respect. I did try to
> get it in sync with the GPSDO and after several minor adjustments and
> several hours of observation, I still saw movement. This isn't that
> important as I can always use the GPSDO as a standard.
> I did find out why it doesn't output a sine wave. There is a nice sine wave
> out of the oscillator itself but that goes through a conditioning amplifier
> and into IC39 which is some kind of 40 pin device. IC39 actually feeds the
> back panel BNC. Why they do this is beyond me but it answers the question.
> I haven't looked at how it behaves coming out of standby yet. I'll let you
> know when I have done that.
>   

Yes, they seem to have made a few oscillator substitutions along the 
way. I'm guessing that they outsourced the oscillators and changed 
suppliers a few times during the life of the 1991/1992 product. I have 
two units, one labelled as having 04A and the other having 04E. Pulling 
info from various manuals, data sheets, and my units, I think the info 
is as follows:

Option Osc. Part # Physical Description - based on my oscillators only
04A 9444* or 11-1710 Approx. cube 5 cm., only one adjustment
04B 9423 Don't know - haven't seen one of these
04E 9462* or 404386 or 454879* Approx 5x5x10cm., two adjustments

* these are the markings on my oscillators. The 04E oscillator is 
actually labelled "9462 454879, Rev. A ERC 87-34". Both of my 
oscillators are 5 MHz with freq. doubler boards attached to the bottom.

IC39 is one of the "Magic happens here" chips in these units. One of my 
units died shortly after I got it. IC39 didn't let the magic smoke out, 
but it was running at a temperature of ~90C! IC39 in the other unit was 
running at ~60C. I decided to put a heat sink on it just in case.

Ed