[time-nuts] Troubleshooting Fluke PM6681
actast at hotmail.com
Sun Aug 16 15:43:39 EDT 2015
I am not sure if this could be related but I have worked on several of these and found the power supply caps can often be a problem and cause the instrument to display a wide range of issues related to the excess PS noise. This problem is more common with the 6681R which runs a bit hotter.
> Date: Sun, 16 Aug 2015 21:16:22 +0200
> From: magnus at rubidium.dyndns.org
> To: time-nuts at febo.com
> CC: magnus at rubidium.se
> Subject: Re: [time-nuts] Troubleshooting Fluke PM6681
> I checked with a former Pendulum employee, and free off memory, he
> recommend trimming up the 100 MHz until Error 2 does not show. Sensing
> it directly can be difficult, FET-probe essentially mandatory.
> Indirectly a 10 MHz is possible. A problem is that trimming with the
> hood off causes a different thermal setup than when the hood is on. If
> you dare, make a hole in the hood so that you can trim it with the hood
> on, that is what they did.
> CMOS backup battery eventually fails, and then you need to replace it
> and re-calibrate it. I have the details jotted down, but it seems that
> this is not your issue.
> On 08/16/2015 12:20 PM, Ole Petter Ronningen wrote:
> > Hello.
> > I have a Fluke PM6681 that has issues. When I got it, it gave results all
> > over the place, but after adjusting the 100Mhz multiplier-chain, it seems
> > to be much better; at least I get std.deviationwell within spec using a
> > split pulse to input A and B, 100 samples. I'd like to get it
> > professionally calibrated, but I don't want to send it in with known issues
> > - the cost of calibration will not be refunded if the instrument can not be
> > calibrated, and I believe it is no longer repairable.
> > So, the issue is that it fails the ASIC test (test 6), with err 2.The
> > service-guide lists a number of signals to be checked in test-mode, but I
> > am not able to see any of them. Since the counter seems to function, I can
> > only conclude that the signals are not present due to this error.. (Or that
> > I am mistreading the guide and looking in the wrong place, probably at
> > least as likely..)
> > Anyway, I cant seem to find a description of this particular error, does
> > anyone know what it means?
> > Thanks,
> > Ole
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