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
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