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 <[email protected]> wrote: > On Wed, Sep 28, 2016 at 4:14 AM, Bob Camp <[email protected]> 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 <[email protected]> wrote: > >> > >> On Tue, Sep 20, 2016 at 12:56 PM, Bryan _ <[email protected]> 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 > >> _______________________________________________ > >> time-nuts mailing list -- [email protected] > >> To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > >> and follow the instructions there. > > > > _______________________________________________ > > time-nuts mailing list -- [email protected] > > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > > and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
