[time-nuts] Lady Heather numbers

Bob Camp lists at rtty.us
Tue Mar 12 20:54:03 EDT 2013


If the oven runs away, you won't get the nice "DAC voltage settling to a reasonable value" trace on LH. If it has run away, the appearance is very distinctive when you open it up. Boards turned brown and highly oxidized solder ….


On Mar 12, 2013, at 7:35 PM, Rex <rexa at sonic.net> wrote:

> Do you think that the oven is working correctly? Is the DC current high on power-up then dropping to a steady lower value after warm-up time?
> My concern is that the resistors may have unsoldered themselves because the oven ran away into an over-temp condition.
> On 3/12/2013 9:55 AM, Garren Davis wrote:
>> Bob,
>> Took your advice and ordered another OCXO. While waiting for it I decided to cut open the
>> OCXO with a bad heater that came with the thunderbolt. I found the 1 ohm resistor from the
>> 12 volt pin to the heater circuit popped off its solder pads and was laying between the
>> insulation and the metal enclosure. While unsoldering the circuit board to fix this the
>> 1 ohm resistor in the oscillator circuit popped off its solder pads. For others that have
>> OCXO's that don't work this is an easy fix. They are large surface mount resistors and easy
>> to solder. Anyways I put the circuit board back in the metal enclosure but did not seal
>> it. I put the OCXO back in my double oven and started a run. The enclosed picture is a 72
>> hour display. Even though the DAC was still increasing it looked like the PPS had stabilized
>> so I did an auto calibrate. You can see this at marker 1. That was almost two days ago.
>> Questions:
>> 1. Is it normal to take this long for the PPS to stabilize?
>> 2. Is it normal for the DAC to keep increasing after two days?
>> 3. In general what numbers would be considered good for the PPS and OSC?
>> Thanks.
>> Garren
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