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

[Tom Miller]

Just put a 47 or 56 ohm resistor from the output pin to ground and look at 
it with a X10 scope probe.

Do you get a sine wave? Over 1 volt pp?

Otherwise, you can open up the can and replace the output chip capacitor.


Regards

----- Original Message ----- 
From: "Scott Stobbe" <scott.j.stobbe at gmail.com>
To: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
Sent: Wednesday, September 28, 2016 2:38 PM
Subject: Re: [time-nuts] Normal operating specs of a Morion MV89?


> If you used a 10x probe (10 Meg || 10-15 pF)  you may have a pretty weak
> output, but if you could drive a meter of coax or a 1x probe to 800 mVrms
> at 10 MHz your probably not too far off spec.
>
> 100 pF at 10 MHz is 160 Ohms.
>
> On Wed, Sep 28, 2016 at 12:39 PM, Tim Lister <listertim at gmail.com> wrote:
>
>> 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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