Philips PM2519 - 3. CHECKING AND ADJUSTING; 3.1. GENERAL

2.6.
2.7.
2.7.1.
2.7.2.
2-23
POWER SUPPLY
The rectified voltage is fed to A1600 (pin 7) and also zener diode V1660. This gives a voltage of 2.7 V on the
minus input of A1600 and gives a negative voltage on the output. Due to this, V1600 and V1601 start
conducting, The voltage on the collector is fed back to the input and is now stabilized by zener diode V1662.
Together with the voltage divider R1602 and R1604, it provides a voltage of +5 V on the collector of V1601.
The +5 V is routed to a level converter which starts to oscillate. {t converts the input voltage to —9 V and
+9 V. The circuit is stabilized with the feed-back circuit consisting of zener diode V1671. V1670 supplied to
V1605.
PM 2519/21
General
The PM 2519/21 version is a standard PM 2519 that inctudes a built-in battery power supply.
The battery power supply part consists of one Pb cell and a circuit that converts the battery voltage into
+5 V, +13 V and ~13 V.
The circuit of the battery power supply can be subdivided into three main parts:
— Charging circuit
As the battery pack is also used in the PM 2521, the level converters and the Schmitt trigger are not used for
the PM 2519/21.
ENABLES CONVERTORS
CHARGING
CIRCUIT
UNSTABILIZED
VOLTAGE
Fig. 2.18. Block diagram-battery power supply Ee not used in PM 2519
Charging circuit (refer to the overall circuit Fig. 7.12)
lf the battery is charged by the power supply (power switch in position “OFF”, PM 2519 connected to the
mains), the voltage on point 2 of X9101 is stabilized by A9101. The output voltage of A9101 is the charging
voltage for the battery.
When the temperature changes, the output voltage is compensated by V9101, so the required charging voltage
is always available.
in the PM 2519, the converters are always disabled by means of two diodes V9202 and V9203. By this means,
the battery is prevented from discharging via the converters.
NOTE: A PM 2519/01 in combination with a PM 9121 will convert the PM 2519/01 into a PM 2519/21.