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

Bob Camp kb8tq at n1k.org
Sat Feb 20 09:11:57 EST 2016


Hi

If this is a double oven, there are two oven circuits and two oven controllers. 
Both would have a set point and both would be adjusted somehow. The pot
may be the adjustment on the outer oven. Get things all set up and packaged,
then adjust the outer oven to make things do what the should do.

Bob

> On Feb 19, 2016, at 7:29 PM, EB4APL <eb4apl at gmail.com> wrote:
> 
> I have read sometime ago and probably on this list a success stories about opening OCXOs using a hot air gun or even a propane torch, an x-acto knife  and a stainless steel shim sheet to avoid the solder to do it stuff again when solidifying.
> Using this technique probably the can could be reused after repairing the part.
> 
> Ignacio EB4APL
> 
> 
> 
> El 19/02/2016 a las 18:09, timenut at metachaos.net wrote:
>> Alex,
>> 
>> I did not take opening pictures, but there is nothing to miss.
>> 
>> For the outside of the unopened case, there are plenty of pictures on eBay.
>> For the actual opening process, that consisted largely of scraping away solder
>> with a small, triangular file and utility knife until most of what I could
>> remove was gone and then using a hammer and screwdriver to separate the sides
>> from the bottom and then prying it off. Nothing pretty, and nothing much for
>> pictures. I used a tiny drill for my desoldering gun to remove an intial hole
>> in the solder for the adjustment hole. I then enlarged it with a 1/16th drill
>> bit (by hand). Ideally, a 2mm drill bit could be used. A 5/64th drill bit will
>> fit through the hole, but it is very tight. Probably not best to drill with
>> it because that would most likely enlarge the hole.
>> 
>> I wouldn't open it the same way again, but I'm not sure of the best procedure
>> that leaves the case and contents undamaged so that it can be reassembled. I
>> think, perhaps, that I would remove all of the solder that I could as before.
>> But then, I would make some sort of cut-out for the pins on the bottom and put
>> it in a pan on the stove and heat it up (hopefully, evenly) until the bottom
>> could be popped off. The outside case can get pretty hot without damage
>> because the only contact is the pins and the inside gets pretty hot when
>> running. The main risk is getting so hot that the plastic spacers on the pins
>> melt or the pin supports melt. I'm not sure how hot that would be. But, they
>> must have heated it fairly hot to melt the solder originally, so hopefully
>> that would work.
>> 
>> However, here are some pictures of the inside :) which is probably what you
>> want!
>> 
>> Top Case 1:    [img]http://imgur.com/mvQkJ16[/img]
>> Top Case 2:    [img]http://imgur.com/K7Rmeau[/img]
>> Bottom Case 1: [img]http://imgur.com/j7tC7QN[/img]
>> Bottom Case 2: [img]http://imgur.com/TKiofvi[/img]
>> Outer Oven 1:  [img]http://imgur.com/bzYywj7[/img]
>> Outer Oven 2:  [img]http://imgur.com/kKKynzc[/img]
>> Outer Oven 3:  [img]http://imgur.com/xtzFsXD[/img]
>> Circuit Board: [img]http://imgur.com/PHgnVIm[/img]
>> 
>> 
>> Mike
>> 
>> 
>>> Hi Mike,
>>> Would you be so kindly and post some pictures of the opening process of
>>> that OCSXO ?
>>> 73
>>> KJ6UHN
>>> Alex
>>> On 2/18/2016 7:54 PM, timenut at metachaos.net wrote:
>>>> Bob,
>>>> 
>>>> The vendor has said that they did not want the unit back. So...
>>>> 
>>>> I opened it up. Crudely, I admit. I learned a few things. I was concerned
>>>> about the outer case heating up too much when I was trying to remove the
>>>> solder. Turns out that the outer case doesn't touch anything except the pins,
>>>> so it can get pretty hot without any damage. Unfortunately, I used a bit of
>>>> brute force to remove the casing after scraping away as much of the solder as
>>>> I could and after cracking the solder seal with a hammer and screw driver.
>>>> Even using more heat, I'm not sure of the best way to remove the case. Neither
>>>> solder wick nor a vacuum desoldering tool is likely to remove all of the
>>>> solder between the top case and the bottom.
>>>> 
>>>> Even so, I got the case off. Somewhat bent, even bent the bottom circuit board
>>>> a bit. I discovered that there is a 2mm hole in the top that allows a variable
>>>> resistor to be adjusted. You need a pretty long, small screwdriver / adjusting
>>>> tool to do that, but that is probably for setting the center point. I would
>>>> try to remove the solder rather than drilling, or drill upside down to prevent
>>>> solder flakes from falling inside.
>>>> 
>>>> Also, I found that the -D on my part number appears to correspond to the board
>>>> revision, which is marked "Rev D". So the -C and -D parts probably have the
>>>> same specifications. And, on the inside there is a marking "92.0" which I
>>>> believe would be the set point for this specific crystal. So if I took the
>>>> crystal out, I would know where to design the set point for a custom unit
>>>> (currently beyond my skills, but who knows...).
>>>> 
>>>>  From there, I removed the bottom casing. That caused additional damage, some
>>>> lifted traces and even one very small part (tiny, SMD, who knows?).
>>>> 
>>>> But, I then soldered wires directly to the board, making patches for the
>>>> lifted traces.
>>>> 
>>>> I plugged it in.
>>>> 
>>>> I turned it on.
>>>> 
>>>> Success!
>>>> 
>>>> I gave it 12v which should supply 2A, but it dropped the voltage down to just
>>>> over 9V. Even so, I got a nice sine wave out at around 4.999790Mhz according
>>>> to my (uncalibrated) scope and around 800mV (into 50 ohm, DC). That was with
>>>> nothing attached to the adjustment pin. After some time, the frequency
>>>> stabilized at 5.000014Mhz and the voltage came back up to 10v. When I attached
>>>> the adjustment pin to ground, there was no change. When I attached the
>>>> adjustment pin to Vref (which is at 6.15v), the frequency dropped to
>>>> 5.000010Mhz. So apparently, these units adjust negatively. But also have a
>>>> very wide adjustment range of 4Hz (8e-7). I am assuming that the adjustment
>>>> range is 0..6v. I attached the adjustment pin to +10v and the frequency
>>>> dropped another 3Hz for a 1.4e-6 adjustment range.
>>>> 
>>>> I don't expect that this specific unit will be very useful given the damage
>>>> that I caused opening it up. But, probably there were just bad connections
>>>> internally, so if I were much more careful in the disassembly, I could
>>>> probably have fixed it. Something to keep in mind for the next unit.
>>>> 
>>>> I may be wrong for what the variable resistor does. Turning it made no
>>>> difference in the frequency.
>>>> 
>>>> I also suspect, but don't know that the difference from 5Mhz is due to the
>>>> frequency counter being uncalibrated. It could also because I damaged the unit
>>>> or just because it is very far off from where it should be.
>>>> 
>>>> Still, I learned a lot, and well worth the time spent.
>>>> 
>>>> 
>>>> Mike
>>>> 
>>>> 
>>>>> 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
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>>>>>>>> 
>>>>>>>> --
>>>>>>>> Best regards,
>>>>>>>> Timenut                            mailto:timenut at metachaos.net
>>>>>>>> 
>>>>>>>> _______________________________________________
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>> 
>> 
>> 
> 
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