GC-1000 problems to solve

[Fredric Newman WA8IDI]

Hello Heath Lovers,
    I just purchased a GC-1000 Most Accurate Clock.  I need to solve the
following calibration problems:
1. Mode #1
    The DATA LED should be off.  It is staying on.
2. Mode #2
    Regardless of what position, anywhere that R444 is set, the PM LED does
not go out.  As the pot is turned to its extremes in either direction, the
LED flickers more and there is a "center" position on the pot where the LED
lights up with relative stability, but again, it does not go out altogether
as the calibration instructions seem to imply it should-"Turn the 1000 Hz
control on the tone decoder circuit board slowly counterclockwise until the
PM LED begins to glow."
3. Mode #2
    Same problem as in Mode #1 but this time with the DATA LED.  According to
the manual, the DATA LED should go out as R434 is rotated to its extremes.
Again, "Turn the 100 Hz control on the tone decoder circuit board slowly
counterclockwise until the DATA LED begins to glow.  No matter where the pot
is set, the DATA LED stays lit.  I therefore can't get a calibration.
    I swapped U402 and U403 with no change in results, which may allow those
ICs to be ruled out as the problem.  I am suspicious of U404, the LM3900, as
it is the audio preamplifier supplying both the amplified 1000 Hz and 100 Hz
tones.  I'm having problems with both of those tones.
    In operation, the CAPTURE LED is coming on when one of the three WWV
frequencies locks on and the appropriate frequency LEDs holds.  The DATA LED
is also flickering.  The clock has not stabilized with a time readout after
running it continuously for about 5 hours.  I know that it can take much
longer to get a time readout, but at this point it appears that something is
not right due to the inability to calibrate the clock in the first place.
    Any assistance in solving this and getting things going with this
interesting Heathkit is greatly appreciated.  Thanks to all.  Fred
Newman/WA8IDI /6

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