[time-nuts] MTI 260-0624-D OCXO

Bob Camp kb8tq at n1k.org
Thu Feb 18 20:10:16 EST 2016


Hi

The one advantage you have in testing a used OCXO is you have a pretty good idea of how
you are going to use it. If phase noise does not matter to you … no need to test. I’d always check
that it tunes on freq with reasonable EFC range left over. I’d also make sure that it warms up 
properly (oven works) and that it has a reasonable output. What goes on the list past that …
it depends on what you need. 

The gear you have will check aging and get it set on frequency fine. It will check it for “wander” 
as your lab heats up and cools down. With a GPSDO and a simple phase lock, a DVM may be
all you really need to do most of that. You will not have a proper ADEV, but you will know it works
pretty well (or not ..).

A lightbulb oven / bench / fridge /freezer proces can give you a wide range TC if you need it. 

If you do get into phase noise, a sound card system will get you going. For ADEV, the 10811’s 
tune far enough that a single mixer system with your 53131 will give you good data. Both 
of those will involve some building, but not a lot of money.

There is one thing about the 10811’s: They are not sealed units. They tend to soak up humidity
when stored in most parts of the country. You may want to run them for a month or three 
before doing any fancy testing.

Bob 

> On Feb 18, 2016, at 7:40 AM, Adrian Godwin <artgodwin at gmail.com> wrote:
> 
> I have a small collection of 10811 and similar oscillators here, collected
> from hamfests rather than china (and mostly pre-ebay).
> 
> What sort of testing regime would you put them through ? I don't have
> anything as exotic as a timepod but I do have an HP53131A, the Tait Rb
> source, and a KS-24361 set up. And always keen to get hints on the
> acquisition of new toys !
> 
> 
> 
> On Thu, Feb 18, 2016 at 12:09 PM, Bob Camp <kb8tq at n1k.org> wrote:
> 
>> Hi
>> 
>> It is *much* better to have an OCXO that you do not need to test to death.
>> There is simply to much testing to do. A modern factory does not test the
>> quality into the product (of any sort) they design in and build it in. The
>> same
>> is true of the normal customer for virtually any component. They make sure
>> the parts come from somebody they can trust and save a lot of testing time.
>> 
>> That said, yes, I have a pile of scrap parts sitting in front of me as I
>> type this.
>> It’s a hobby. Time does not count. It lets me play with all sorts of toys
>> doing
>> the testing. I occasionally learn things in the process. Mostly I learn
>> that
>> my hope of a 100% perfect batch is still a dream ….
>> 
>> Bob
>> 
>> 
>> 
>>> On Feb 17, 2016, at 9:56 PM, timenut at metachaos.net wrote:
>>> 
>>> Bob,
>>> 
>>> In this case, I know how it was taken off the board - it wasn't. They
>> just cut
>>> the board around it. I had to remove it myself. Nice thing about that,
>> is that
>>> I got a nice plastic, pre-formed part that fits between the board and the
>>> OCXO, probably as an insulator.
>>> 
>>> You are also right about the number of things that you need to test to
>> make
>>> sure that one of these is fully functional. However, this is a "starter"
>> OCXO
>>> for me and I don't yet have the equipment to perform the tests. The best
>> that
>>> I can do is to make sure that, when powered up
>>> 
>>>  1. I see something that sort of looks like a sine wave at a reasonable
>>>     magnitude.
>>> 
>>>  2. My 2465B CT frequency counter thinks that it is somewhere near 5Mhz.
>>> 
>>>  3. If I apply gnd, or VRef to the adjustment pin I see the frequency
>> change
>>>     at least a small amount.
>>> 
>>> Without more equipment, there isn't much more that I can do to test.
>> Unless
>>> you have some suggestions?
>>> 
>>> 
>>> Mike
>>> 
>>> 
>>>> Hi
>>> 
>>>> Best guess is these things get taken off the board with either a big
>> torch or a charcoal fire.
>>>> You can ask Mr Google to dig up pictures of the process. Depending on
>> just how quick
>>>> they are, the insides of the OCXO can easily be reflowed. The
>> likelihood of it reflowing and
>>>> cooling back to a reliable joint … not real good.
>>> 
>>>> Bob
>>> 
>>>>> On Feb 17, 2016, at 5:16 AM, Andrea Baldoni <erm1eaae7 at ermione.com>
>> wrote:
>>>>> 
>>>>> On Tue, Feb 16, 2016 at 07:58:21PM -0500, timenut at metachaos.net wrote:
>>>>> 
>>>>>> I just received a 5Mhz OCXO from eBay (MTI 260-0624-D OCXO). After
>> testing it,
>>>>>> it is clear that it is defective.
>>>>>> 
>>>>>> 1. It never heats up.
>>>>>> 2. The reference voltage is zero.
>>>>>> 3. Only noise is seen on the output pin.
>>>>> 
>>>>> I had the same issue with some of them. It's very likely that the
>> internal
>>>>> solder connections from pins to PCB are broken, at least, the one for
>> power.
>>>>> It happens because the inner oven is heavy and there isn't any thermal
>>>>> insulator (besides air) to keep it from moving.
>>>>> 
>>>>> Wheter the crystal has been damaged or not, it's unknown. I had one
>> where the
>>>>> crystal actually fell off from its supports too.
>>>>> 
>>>>> I posted a link to photos of the internals, time ago. The link is dead
>> now
>>>>> and I don't think to have the photos anymore but perhaps someone
>> downloaded
>>>>> them.
>>>>> 
>>>>> Best regards,
>>>>> Andrea Baldoni
>>>>> _______________________________________________
>>>>> time-nuts mailing list -- time-nuts at febo.com
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>>>>> and follow the instructions there.
>>> 
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>>> 
>>> 
>>> 
>>> --
>>> Best regards,
>>> Timenut                            mailto:timenut at metachaos.net
>>> 
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