Thanks for the correction, Bruce. I made the mistake of thinking that
the Bridge Section was the only thing inside the puck. I should have
looked further.
Ed
On 1/9/2012 12:47 PM, Bruce Griffiths wrote:
Ed Palmer wrote:
On 1/9/2012 8:58 AM, Robert Benward wrote:
Hi Ed,
I just tracked down Fluke and he offered me one, and per your advice
I will try and confirm the condition before purchasing from him (not
that there are alternate sources) .
I have to say that fluke.l did guarantee that the E1938A was alive
and it was. According to other messages on this list, he's been very
good about replacing defective items.
I have the schematics, but taking apart the hocky puck is another
matter, I pry and pry but get nowhere. I don't think it was
designed to take apart. What buggs me is that if I warm up the oven
and stimulate the oscillator with an external signal, it will
oscillate. So it DOES work, and if I go into the puck to trouble
shoot it, I probably won't find anything defective.
Are you certain that the problem is inside the puck? If I'm reading
the schematic correctly, the only thing in there are the crystal and
a few passive components. The oscillator circuit is on the external
board. A bad connection or failed component could be interfering
with the oscillation. When the puck is hot, it's almost able to
overcome the external problem and your stimulus signal is enough to
get it going.
Wrong, the oscillator is within the oven, its buffer amplifier is
outside the oven.
Everything shown on the first schematic is inside the oven.
When your E1938A is working, is it working properly, on frequency and
good stability? If so, that would suggest that the crystal is okay.
The problem could be nothing more serious than a bad solder joint.
I've noticed that precision oscillators have something of a 'diva'
personality and can be quite temperamental. I have an Oscilloquartz
BVA oscillator that takes 5 - 10 seconds to start up after you apply
power.
Have you asked Rick Karlquist for advice on dissecting your E1938A?
He's an active member of this list and one of the designers of the
E1938A. You might want to start a new message thread called
something like 'E1938A repair' to get the attention of the right people.
Ed
Bruce
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