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

Alex Pummer alex at pcscons.com
Wed Feb 17 23:29:30 EST 2016


Hi Mike,
look for any kind of radio-receiver, which would receive around 5MHz the 
old 60 meter broadcast ban, connect to power any kind of wire which 
could serve as antenna turn it on and try to find WWW at 5MHz, after 
that power up your 5MHz oscillator connect piece of wire to the 5 MHz 
output and bring the other end close to the radio receiver's "antenna" 
which you installed before. I you are lucky you will hear a beat from 
the radio's speaker, now you could apply some tuning voltage to your 
oscillator, and if you change that tuning voltage the beat will change 
somewhat but no to much since that OXCO has  very narrow tuning range. I 
t could also happen that you do not hear any beat frequency, but a 
wabling [= very low frequency fluctuation] of the www, because your 
oscillator's and the frequency of the  www are very close to each other, 
frequency of beat is not audible. the frequency of the www will be not 
exact since it's propagation path is not stabile. That is enough to see 
of the OXCO is still "alive" and with a proper PLL it could be tuned to 
the correct frequency
73
KJ6UHN
Alex

On 2/17/2016 6:56 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
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