[time-nuts] Troubleshooting Fluke PM6681

davidh dhooke at gmail.com
Sun Aug 16 16:27:29 EDT 2015


I have a few of these counters and would love to see the details of the 
calibration process you mention.



On 17/08/2015 5:16 AM, Magnus Danielson wrote:
> Ole,
> 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.
> Cheers,
> Magnus
> 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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