[time-nuts] MTI 260-0624-D OCXO
wb6bnq
wb6bnq at cox.net
Fri Feb 19 02:18:52 EST 2016
Mike,
Way more likely that "POT" set the temperature of the oven.
Bill....WB6BNQ
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
>>>>>>>_______________________________________________
>>>>>>>time-nuts mailing list -- time-nuts at febo.com
>>>>>>>To unsubscribe, go to
>>>>>>>
>>>>>>>
>>>>https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>>>
>>>>
>>>>>>>and follow the instructions there.
>>>>>>>
>>>>>>>
>>>>>>_______________________________________________
>>>>>>time-nuts mailing list -- time-nuts at febo.com
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>>>>>>
>>>>>>
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>>>>
>>>>>>and follow the instructions there.
>>>>>>
>>>>>>
>>>>>
>>>>>--
>>>>>Best regards,
>>>>>Timenut mailto:timenut at metachaos.net
>>>>>
>>>>>_______________________________________________
>>>>>time-nuts mailing list -- time-nuts at febo.com
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>>>>>
>>>>>
>>>>https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>>>
>>>>
>>>>>and follow the instructions there.
>>>>>
>>>>>
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>>>>
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>>>
>
>
>
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>
>
>
>
>
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