[Test-Equipment] Kikusui Freq. Counter problem

[Howard Weeks]

Bob,

If the boards are mounted in sockets, try removing them one at time, 
wipe the contacts and replacing them. I have a lot of HP and Tektronix 
test equipment that has seemingly went crazy at times. That has fixed 
mine every time over the last 10 years or so.

I would guess that the board contacts are trying to corrode on me.

I have an HP counter that works similar to the one you have and it went 
crazy last year. The first two boards I pulled corrected the problem for me.

Howard K5JCP


On 01/20/2020 11:05 AM, Robert Nickels wrote:
> I'm scratching my head over a weird problem with a Kikusui FCO1130 1GHz
> reciprocal type frequency counter.    This type of counter works by
> counting both the unknown input signal and the 10 MHz timebase, and
> calculating either frequency or period with its microcontroller.    The
> counter is basically working and can even - sometimes - display the
> correct frequency, but the result varies with the  setting of the Gate
> Time control.   This is just a pot connected to a multivibrator that
> generates a pulse that tells the MCU when to make a measurement, the
> longer the setting the greater the number of pulses that get counted and
> thus the better the accuracy (at the cost of a longer interval between
> display updates).     The Gate Time control is variable from 100 ms to
> 10s, and should only impact the resolution, but in this counter it
> changes the value of frequency or period that is displayed (which should
> not happen).
>
> The 10MHz TCXO output is clean and stable, there was a bit of ripple on
> the power supply so I replaced the filter cap but it had no effect. The
> problem does not change as a function of input signal strength or
> frequency, and happens on both the direct and prescaled VHF-UHF range
> input.    There is a "check" switch that switches the input to the 10MHz
> timebase which should always display 10 MHz of course, but changing the
> Gate Time control can vary it hundreds of kHz.     I'm puzzled because
> this part of the counter function should be primarily implemented in
> firmware!
>
> Kikusui provides an operators manual with a bit of theory and
> calibration info but no schematic.   So I thought I'd see if anyone
> might have tangled with this beast before, or similar reciprocal counters.
>
> Thanks and 73,
> Bob W9RAN
>
>
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