Patek Philippe CALIBER CH 28-520 QA 24H User manual

CALIBER CH 28-520 QA 24H
CALIBER CH 28-520 IRM QA 24H
annual calendar chronograph

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INDEX

CALIBER CH 28-520 QA 24H
annual calendar chronograph

caliber ch 28-520 Qa 24h
annual calendar chronograph

b a c k
f r o n t

CALIBER CH 28-520 IRM QA 24H
annual calendar chronograph

caliber ch 28-520 irM Qa 24h
annual calendar chronograph

b a c k
f r o n t

CALIBER CH 28-520 QA 24H
CALIBER CH 28-520 IRM QA 24H
annual calendar chronograph
ENGLISH

15
TRADITION AND
INNOVATION
IN PERFECT HARMONY
The CH 28-520 IRM QA 24H chronograph
caliber is a self-winding mechanical move-
ment with a flyback column-wheel chronograph,
power-reserve indicator, Annual Calendar, and
day/night display. The CH 28-520 QA 24H caliber
has the same features, with the exception of the
power-reserve indicator. Both movements beat
at a frequency of 28,800 semi-oscillations per
hour (4 Hz), assuring an extremely constant bal-
ance amplitude and high rate accuracy. The wind-
ing power is delivered by a heavy, unidirectional
21K gold rotor. And both chronograph calibers are
based on the venerable column-wheel principle
for controlling the start/stop commands. However,
it differs from classic Patek Philippe column-wheel
chronographs by virtue of a remarkable innova-
tion: the clamps do not control the engagement
of a lever-mounted clutch wheel with the chrono-
graph train but instead act on a disk clutch that
transmits (chronograph running) or interrupts
(chronograph stopped) the power between the
fourth wheel and the chronograph hand. This is
a highly reliable solution that makes it possible
to use the chronograph hand as a continuously
running seconds hand without affecting the rate
accuracy of the watch. For this reason, the sub-
sidiary seconds dial customarily found in many
chronographs is no longer needed.

16 INSTRUCTIONS
winding crown
The winding crown is used to wind the watch
(position 1) and to set the time (position 2).
winding
Your watch incorporates a self-winding movement.
The movements of your wrist set a centrifugal mass
in motion; this tensions the mainspring which
stores the energy. When you take off your fully
wound watch, it will continue to run for at least
45 hours. When it has stopped after depleting the
power reserve, it can be rewound by hand (about
10 clockwise turns of the crown). Please wind the
watch before you put it on. This way, you can avoid
lateral pressure on the winding stem which in the
course of the years could damage the stem tube.
setting the time
To set the time, pull the crown out to position 2,
and turn it in either direction. When you turn the
hands clockwise beyond midnight, the calendar
displays will advance as well. We advise against
turning the hands counterclockwise across mid-
night because this would desynchronize the cal-
endar displays; however, it would not damage the
calendar mechanism. When the correct time is set,
push the crown home again.

17
Caution: Please set the time before you put the watch on.
This prevents lateral pressure on the winding stem. Please
use your fingernails to pull the crown out and turn it gently
between two fingertips.
Never pull the crown out in a humid environment or under-
water: the water resistance of your watch is assured only
when the crown is pushed home.
chronograph
The chronograph is started and stopped with the
button at 2 o’clock. The chronograph hand as well
as the minute- and hour-counter hands are reset to
zero with the button at 4 o’clock. The same button
controls the flyback function during an ongoing
time measurement. When you push the button at
4 o’clock while the chronograph hand as well as
the minute- and hour-counter hands are running,
this will cause all hands to fly back to zero and
instantly start a new measurement. In other words,
the stop and restart functions are combined.
Conversely, if you first stop the chronograph hand
as well as the minute- and hour-counter hands by
pressing the button at 2 o’clock, the actuation of
the button at 4 o’clock will cause all three hands
to return to the zero position and stay there.

18 ANNUAL CALENDAR
function and corrections
Your watch incorporates an Annual Calendar
with aperture displays for the day of the week,
the month, and the date; it automatically recog-
nizes months with 30 and 31 days. If the watch is
worn daily, the date only needs to be corrected
on March 1 (forward by 3 days in non-leap years,
and by 2 days in leap years). A calendar correction
may also be necessary if the watch was set aside
for a longer period of time and stopped running. If
the hands are moved clockwise beyond midnight,
the calendar displays will advance by one day. For
quick corrections, the three aperture displays can
be adjusted individually with the three push pieces
in the case flank between 9 and 10 o’clock.
Caution: The mechanism that advances the calendar dis-
plays is active every day between 8 p.m. and 2 a.m. During
this period, the calendar should not be adjusted with the push
pieces. To avoid the risk of interfering with the mechanism
when performing adjustments, set the watch to 6 a.m. as fol-
lows: turn the hands beyond midnight (the date will switch;
otherwise, advance them from noon by another 12 hours) and
then set them to 6 a.m.
If your watch has stopped running, rewind it by hand before
performing any corrections or adjustments (about 10 clock-
wise turns of the crown).
The push pieces should be actuated only with the correction
stylus delivered with the watch. The use of any other tool
could damage your timepiece.

19
date correction
To set the date, actuate the correction push piece
between 9 and 10 o’clock as many times as needed
to display the current date.
If you wish to set the date to the 30th or the 31st,
proceed as follows:
1. Make sure neither the 30th nor the 31st is indi-
cated (if necessary, set the date to the first day
of the month).
2. First, correct the month with the push piece at
10 o’clock (see below).
3. Then correct the date to the 30th or the 31st.
The mechanism that advances the month display is
already active on the 30th and the 31st. If you do
not follow the described procedure, the calendar
might be desynchronized, but the integrity of the
mechanism would not be affected.
month correction
To correct the month, actuate the correction push
piece at 10 o’clock as many times as needed to
display the current month.
day of week correction
To correct the day of the week, actuate the push
piece at 9 o’clock as often as needed to display
the correct day.

20
Position 1:
Winding
Position 2:
Setting the time
Date correction
Month correction
Day correction
Chronograph
start/stop button
Chronograph reset
and flyback button
1 2
The diagram applies to all watches with CH 28-520 QA 24H
and CH 28-520 IRM QA 24H calibers.