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

Tim Lister listertim at gmail.com
Wed Sep 28 12:39:17 EDT 2016


On Wed, Sep 28, 2016 at 4:14 AM, Bob Camp <kb8tq at n1k.org> wrote:
> Hi
>
> You have one of the many MV89A’s with an output problem. To be absolutely
> sure of the output, you need to have the scope set to 50 ohm input. If it was set
> to Hi-Z, the output is likely even lower…..

It seems that the scope is 1 MOhm input impedance and is not
changeable. I will have to see if we have any 50 Ohm in-line
terminators around that I can also borrow. Does anyone think that
there is any value in trying to pursue a return and replacement with
the ebay seller (being China, it's likely to be a long round-trip time
for both messages and parcels) or just live with it and move on
(potentially replacing the capacitor later if I get some way of
getting the casing open safely). From what Bob and others have said,
it seems that most of the MV89's have this problem so it seems
unlikely I would get a better one without a lot of trials.

Tim

>
> Bob
>
>
>> On Sep 28, 2016, at 1:38 AM, Tim Lister <listertim at gmail.com> wrote:
>>
>> On Tue, Sep 20, 2016 at 12:56 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=-
>>>
>>
>> I managed to borrow a Tek TDS 2024B 200 MHz scope from work and hooked
>> it up to the output of my MV89A. I get a peak-to-peak measurement of
>> 2.3 V which if I have converted it right is ~11 dBm ? Alternatively if
>> I turn on the FFT mode on the scope I get a peak value of -2.17 db if
>> I am driving the cursor mode correctly. With the 10 MHz from the
>> radioshackus GPSDO used for triggering, it takes ~18 seconds for the
>> MV89 waveform to drift 1 cycle (this is without anything connected on
>> the Uin or Uref pins).
>>
>> Tim
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>
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