[time-nuts] Normal operating specs of a Morion MV89?

Bob Camp kb8tq at n1k.org
Tue Sep 20 18:09:17 EDT 2016


Hi

At least the MV89’s that I have bought have been mostly defective. The issues in them are many
and some of them are only apparent with fairly exotic testing There are a lot with defective output 
capacitors, but many of those also have other issues as well. Unless you have a lot of time, repairing 
them is not very cost effective. 

Basic gear to check one out:

Temperature test chamber to spot the miss-set temperature controllers
Phase noise test set to spot the various noisy stages
ADEV test to check the noisy temp controllers
Output level test / harmonics via spectrum analyzer

That’s just a quick list of the stuff I ran them past. Different ones failed different tests. 

Note: These are pretty good OCXO’s. The guys that make them are doing a good job. The problem 
is the salvage process they go through. You need to be pretty careful dealing with an OCXO. The
salvage guys are not careful at all. They damage far more parts than they save ….

Bob


> On Sep 20, 2016, at 5:41 PM, Bryan _ <bpl521 at outlook.com> wrote:
> 
> Any tips on resoldering the can, special solder or flux required? Quite often they can be found for a good price on Ebay, from what I have read they are a  good OCXO minus the issue of the one particular cap failing.
> 
> -=Bryan=-
> 
>> From: brayniac at gmail.com
>> Date: Tue, 20 Sep 2016 20:06:59 +0000
>> To: time-nuts at febo.com
>> Subject: Re: [time-nuts] Normal operating specs of a Morion MV89?
>> 
>> Yes. This low output due to capacitor failure is a very common failure.
>> From the last set of MV89a I got on the bay, all had this issue.
>> 
>> I had good luck opening mine with a hot air rework station with a small
>> nozzle to blow the solder seal away. A bit of careful prying with a thin
>> flat screwdriver while it is still hot to pop the bottom from the case. The
>> capacitor is easy to get to once the outer can is removed. Hot air to
>> remove. Then tweezers and a fine point soldering pencil made for an easy
>> repair.
>> 
>> Obviously, be very careful and be sure to work on an appropriate surface
>> for the amount of heat involved.
>> - Brian
>> 
>> On Tue, Sep 20, 2016, 12:57 PM Bryan _ <bpl521 at outlook.com> wrote:
>> 
>>> May also want to check the output amplitude. If memory serves me correct
>>> it is very common for a capacitor inside this model number to fail. It can
>>> be fixed but requires a torch or a pretty heavy duty soldering iron to get
>>> the can open.
>>> http://www.rbarrios.com/projects/MV89A/
>>> 
>>> -=Bryan=-
>>> 
>>>> From: listertim at gmail.com
>>>> Date: Mon, 19 Sep 2016 14:31:06 -0700
>>>> To: time-nuts at febo.com
>>>> Subject: [time-nuts] Normal operating specs of a Morion MV89?
>>>> 
>>>> I recently ordered and received what claims to be a 2007 vintage
>>>> Morion MV89 from ebay (I say claimed as that what the auction item
>>>> said, but my unit is missing the identifying label on the top and just
>>>> has '2007 MV89A' written on the side in marker). I've powered it up
>>>> with a bench power supply at 12V and it's drawing 390mA at steady
>>>> state. I measured the case temperature with a ThermaPen Mk4 (not often
>>>> I get to combine the hobbies of bbq and timenuts...) which is
>>>> calibrated to +/-0.7F to be about 111F, varying somewhat with
>>>> position.
>>>> 
>>>> This seems pretty hot - Is this normal ? The datasheet says it should
>>>> draw <350mA when at steady state but doesn't say what temp it should
>>>> be at. Does anyone else have info on their version to see whether this
>>>> is normal ?
>>>> 
>>>> Cheers,
>>>> Tim
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