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A-711/711L
ADJUSTMENT
Timer accuracy
improvement
method
1C5(X05—)
CXPS0112-1270
Qt
-2SK241
High-impedance
FET probe
"Unless available, make it for yourself.
Frequency counter
The timer accuracy is within +40 seconds for one month
as a standard. For improved timer accuracy, perform the fol-
lowing procedure:
:
(1) If the timer accuracy is without the standard, replace X3
(L77-1175-05) near the microprocessor IC on a printed
board (X05-}.
(2) Even if within the standard, for further improved accura-
cy, change the constant of C99 in the crystal oscillation
circuit of microprocessor IC5 and add a trimmer.
Adjustment method
(Use a high-impedance buffer to avoid
frequency deviation.}
Connect a high-accuracy frequency counter to pin 74 by way
of the FET probe shown above, and adjust the frequency fully
up to the first digit of the X3 reference frequency 4,194,304 Hz.
(Connect the negative (—} side of the frequency counter to the
GND side of C99.}
Note {a} As regards the positive (+) side of the frequency
28
counter, arrange as short a distance as possible be-
tween pin 74 of IC5 and 1P of the input stage of the
FET probe.
Capacitance
value of
additional
trimmer
C8 constant
modification
22 pF titanium
capacitor
(CC45FCHTH220J)
20 pF (red),
C05-0303-05
Qi:
2SK241(GR,
BL)
4: Drain (D)
12
3
2: Source (S)
out
sh
{View from leg sida).
Additional trimmer
= q
Modification
7 ~~
77 7 7
=
1
'
99
ete So
{Changed to 22 pF |
Note:
Disconnect the C99 connected on
the X05 board, and add a trimmer.
{it is necessary to make a hole.)
Next,
connect
a 22 pF titanium
input:
1 MQ
capacitor on the rear.
Note (b) Perform the trimmer adjustment after energization of
around 10 minutes at normal temperature.
{3} Monthly error calculation method
For example, when the result of measurement at pin 74
by the frequency counter is fx=4,194,275 Hz...
(Reference frequency fo = 4,194,304 [Hz}}
x the number of seconds
Monthly error [sec] = ae
taken fer one month
4,194,275
- 4,194,304
4,194,304
x (60 x 60 x 24 x 30)
— 17.9 {sec] _
*A minus value as the monthly error
means a loss.
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