[time-nuts] HP 10811 update

Bob Camp lists at rtty.us
Fri Jul 26 08:52:15 EDT 2013


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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