[time-nuts] HP 10811 update

[paul swed]

Good comments. Indeed I will order up a new xtal from digi-key. They should
be in stock any day now. I do agree with the comment on the cap in
parallel. I had not thought about the series cap dropping and there is a
.1uf as I recall. Need to look. The varicap seems to work very well so
don't believe thats an issue.
Will do some more hunting.
By the way as a heads up the top and bottom cover of the xtal compartment
are actually a pain to screw back together.
Anyone have a sense of the Hz change per degree C?
Thanks


On Fri, Jul 26, 2013 at 8:52 AM, Bob Camp <lists at rtty.us> wrote:

> Hi
>
> Ok, since it's moved *down*  and it's about on temperature there are a
> couple of likely possibilities:
>
> 1) The crystal leaks and there's air in it
> 2) The trap coil(s) / capacitor(s) have changed value
> 3) The varicap is shorted / forward biased
>
> Normal factory troubleshoot (after checking the varicap) would be to swap
> the crystal and see if the problem follows the crystal or the oscillator.
> Yes, I know, that's not very helpful in this case - sorry about that.
>
> Bob
>
> On Jul 25, 2013, at 9:32 PM, paul swed <paulswedb at gmail.com> wrote:
>
> > Well lucks not so good do have the voltage closer but as Bob C said. That
> > ain't the issue.
> > Darn I hate when he is right. By the way the oscillator draws 26 ma
> approx
> > as a reference. Reassembled everything and let the oven heat up it
> settles
> > at 81C 15 min after start and within a respectable range of the temps
> > listed in the service manual. Measured with a K thermocouple. Freq is at
> > 9.999955. or 45 Hz low
> > Tuning the variable cap has 20 Hz range and the cap was pretty much
> center
> > range. Have not played with the varicap but that should have a very small
> > effect.
> > I can easily adjust the temp setting R to raise the xtal temp. But that
> > seems like a jerry rig.
> > Could a xtal of this quality simply go bad over time?
> > Somewhat at a loss here.
> > I have a spare 10544 (Would not use the z3801 outer oven)and wonder if at
> > least I could use that with the Z3801. Anyone know if the efc would work?
> > Regards
> > Paul
> > WB8TSL
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > On Thu, Jul 25, 2013 at 10:28 AM, Stefan Heinzmann
> > <stefan_heinzmann at gmx.de>wrote:
> >
> >> paul swed wrote:
> >>
> >>> I can't believe you found the transistor. When I pulled it out last
> night,
> >>> its actually a MPSA18!!! I had not had time to look it up but figured
> it
> >>> was a ebay leftover hunt. :-)
> >>> At that price I may order 20 of them. Like the gain.
> >>>
> >>> Toshiba used to make a transistor with even higher gain, the
> >> 2SC3112/2SC3113/2SC3295/**2SC4666 (same chip, different package). They
> >> discontinued it recently, however.
> >>
> >> Cheers
> >> Stefan
> >>
> >>
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