Matsui 1410R, 1410T, 2010T Schematic

SERVICE MANUAL

Manual Number: 668200

MATSUI 1410R/1410T/2010R

TV

Version 1.1

This Manual is available in Electronic format.

Mastercare, Maylands Avenue, Hemel Hempstead, Hertfordshire, HP2 7TG, Telephone [phone]

MATSUI 1410R/1410T/2010R

TV

SERVICE MANUAL

Specifications are subject to change without notice.

COPYRIGHT © 2000 MASTERCARE LIMITED

PRODUCED BY

MASTERCARE TECHNICAL CENTRE

Contents

Technical Specifications Page 2
Mechanical Instructions Page 3
Overview oscillograms / testpoints Page 4
Descriptions of microprocessor and TXT in CTN chassis Page 5
Small signal Page 7
Power supply Page 9
Power supply signal Page 10
Electrical Adjustments Page 11
Repair Facilities Page 12
Block Diagram Power Supply Page 13
List of Abbreviations Page 14
Electrical Instructions Page 15
Safety Instructions, Maintenance Instructions, Warnings and notes Page 17
PCB layout Page 18
Block Diagrams Page 20
Circuit Descriptions Page 26
Parts List Page 33

Technical specifications

CHASSIS CTN

Mains voltage : 220 - 240 V ± 10% AC; 50 Hz (±5%)
Power cons. at 220V~ : 35 W (stand-by 6W)
Aerial input impedance: 75Ohms - coax
Min. aerial input VHF : 30:V
Min. aerial input UHF : 40:V
Max. aerial input VHF/UHF : 180mV
Pull-in range colour sync. : ± 300 Hz
Pull-in range hor izontal sync. : ± 600 Hz
Pull-in range vertical sync. : ± 5 Hz
Picture tube range : 14''

: Mono 4'' round full range 25W 1W.

TV Systems : PAL BG

Indications : On screen display (OSD) green and menu

VCR programs : 0 to 79
Tuning and operating system : VST
UV1315AS / IEC (VST) : VHFa: 48 - 102 MHz

U1343AS / IEC (VST) : UHF: 470 - 861 MHz
Local operating functions : Vol/Prog, +, -, contrast, colour and brightness.

: PAL I
: PAL BG / SECAM BGDK
: PAL BGI / SECAM BGLL'

: 1 LED (red in ON and blinking red in stand-by)

: VHFb: 138 - 224 MHz
: UHF: 470 - 861 MHz

2. Connection facilities

Euroconector:

Green

R (0V5 RMS ó 1K ). 17 - CVBS

R (0V2 - 2V RMS ò 10K ). 18 - CVBS

L ( 0V5 RMS ó 1K ). 19 - CVBS

L (0V2 - 2V RMS ò 10K ).

(0-2V int., 10-12V ext.).

(0V7

1 - Audio

2 - Audio

3 - Audio

4 - Audio

5 - Blue

6 - Audio

7 - Blue (0V7pp/75W ).
8 - CVBS status 1

9 - Green

10 - -

11 ­12 - ­13 - Red

14 - ­15 - Red (0V7
16 - RGB status (0-V4 int.) (1-3V ext. 75W ).

20 - CVBS

21 -

Earthscreen.

pp

/75W ).

Head phone:

pp

/75W ). 8 - 600

1

( 1Vpp 75W ).

( 1Vpp/75W ).

S

/60mW 3,5mm

ø

.

Mechanical instructions

For the main carrier two service positions are possible (3.1).

A: For faultfinding on the component side of the main carrier.
B: For (de) soldering activities on the copper side of the main carrier.

Position A can be reached by first removing the mains cord from it's fixation, then loosen the carrier lips (1) and then pulling the
carrier panel (2) for approximately 10cm.

Position B can be reached from position A after disconnecting the degaussing cable. Put the carrier on the line transformer side.

Fig. 3.1

Fig. 3.2

2

Overview oscillograms / Testpoints

3

Description of microprocessor and TXT in CTN chassis

MICROPROCESSOR + TXT
The CTN model chassis is designed to accept three different microcontrollers: the TMP47C634, the SAA5288 and the SAA5290.
The three microcontrollers are mounted in the same position, by placing pin 1 at the same point. The TMP47C634 has 42 pins while the SAA52XX

models have 52 pins. The circuitry connected to the pins is practically the same. From pin 21 on the Toshiba model, the equivalent pin on the
SAA52XX unit will be 10 numbers higher (e.g., pin 33 on the TMP47C634 corresponds to pin 43 on the SAA52XX).

The difference between the TMP47C634 and the SAA52XX is an improvement in the OSD (it goes from two lines to a full screen, thus making it
possible to implement the MENU) and the addition of new functions in the software (24-h timer, child block, etc.). The SAA5290 also has a TXT
decoder.
Following is an explanation of the different functions of the microcontrollers with indications as to the pin number assigned to each integrated circuit
and the differences between the microprocessors, where applicable:

- Integrated circuit power supply: The TMP47C634 has a single +5V power supply (pin 42 VVD). The SAA52XX has several power supplies for the
microcontroller (pin 44 VDDM), the analog converter and the OSD (VDDA pin 38 and VDDT pin 39), as well as for the final phase of RGB outputs
(RGBREF pin 31).

- LED (pin 20): The LED lights up with a low current when the television set is ON and with a high current when the set is on Standby.

- RC5 (pin 35 on the TMP47C634; pin 45 on the SAA52XX): The commands transmitted by the remote control handset are received by infrared
receiver 1685 and passed to the microcontroller for decoding.

- Switching voltages of the BG/L-L/L’-BG/I systems (pins 36, 37 and 38 on the TMP47C634; pins 46, 47 and 48 on the SAA52XX). Th ese signals are
only used on Multistandard units. These pins are used for switching the system f or decoding sound and video. These signals are inv erted and set at
the correct level by transistors 7672 and 7673, respectiv ely. Once they are transf ormed, together with the signal from pin 48 (BG/I), they make up the
system status lines (See table).

- Oscillator: The TMP47C634 has a 4-MHz oscillator which is determined by a 4-MHz ceramic resonator on pins 31 and 32. The SAA52XX has a 12­MHz oscillator which is determined by a 12-MHz crystal between pins 41 and 42.

- On-Screen Display (OSD): In order to synchronize the OSD information with the picture signal, the VERT FLYBACK signal is added in inverted
form to the integrated circuit (pins 15 and 27 on the TMP47C634 and pin 37 on the SAA52XX), as is the HOR FLYBACK signal (pin 26 on the
TMP47C634 and pin 36 on the SAA52XX). The SAA5290 also uses these signals to synchronize the TXT. On the TMP47C634 there is an LC
network on pins 28 and 29 which controls the OSD.
The TMP47C634 has only the green output activated (pin 23) and this is inverted with transistor 7658 so that the correct level is reached. The
SAA52XX models have three outputs, R, G and B (pins 32, 33 and 34) with emitter followers (7641, 7642 and 7644).
The pin for erasing the RGB picture signal for inserting OSD (pin 25 on the Toshiba and 35 on the SAA52XX) is connected with diode 6679 to pin
21 on the TDA836X.

- Tuning: The unit has a VST (Voltage Synthesized tuning) system. This system wor ks by tuning to a station on the tuner through a linear variation
of the tuning voltage (0V2 to 5V). It is a vailable on pin 1 of the mC and converted to an adequate lev el on the selector/dial (0V to 33V), using T7605
and +101.5V. The AFC signal (Automatic Frequency Control) of detector FI is added to the tuning voltage V-VARI by R3689 and R3688 to compen­sate for the slow variation of the tuning feature.
While searching for the station, pin 41 is set on high which means that the AFC voltage will not be added to the V-VARI. If an IDENT signal is
received on pin 16 while searching for a station, the mC will check via entry pin 9 whether the tuning is correct and whether the AFC signal can be
activated again. The SAA52XX has 3 pins (15 VHF1, 17 VHFIII AND 18 UHF) for band switching and provides v oltage to the corresponding pin. The
TMP47C634 has only two pins (17, 18) for band switching which decode the 3 tuning lines using transistors 7003 and 7004.
The SAA52XX models also have pin 30, which they use to limit the CAS voltage in automatic tuning so that noise signals are not memorized.

- Picture and sound adjustments: volume control (pin 2), brightness control (pin 3), colour control (pin 4) and contrast control (pin 5); the SAA52XX
models also have sharpness control (pin 6).

4

The RC networks are used to convert the modulated pulse output to a DC voltage level. Some of these settings can be preprogrammed in the
memory for all channels as a personal preference (PP). Mute is controlled internally on the mC during automatic station search or when the signal
received is interrupted (detected via the IDENT signal on pin 16).

- Service: If pin 7 is connected to earth when the set is tur ned on from the IR, the unit will go into Service Default Mode (see Chapter 8).

- INT/EXT and mute on programme 0. The microcontrollers hav e a pin for s witching to external (pin 7 on the TMP47C634 and pin 8 on the SAA5290)
via transistors 7876 and 7877. This signal is added to the signal from SCART pin 8 so that either of them can be used to switch to external.
On units without SCART, this signal is used for muting the sound and picture on programme 0.
On the SAA52XX models, this line is also an input line so that the microcontroller knows if the unit is on external. This way, the correct video signal
is switched on the TXT and the sound is not muted on external, even if there is no pilot signal.

- EEPROM bus 12C memory (pins 39 and 40 on the TMP47C634; pins 49 and 50 on the SAA52XX); The microcontroller is connected to non-volatile
memory IC7685 (EEPROM) via bus 12C. Personal preferences (PP) and channel data are stored in the memory. The system can memorize 79
channels (with the data on tuning voltage, band and system) and the personal preferences.

- Standby (pin 19); The Standby switching signal is on pin 19 of the mC . If the Standby signal is “low”, it reduces the start-up voltage of oscillator pin
36 on the TDA836X, thus cutting the line voltages.

- Control and options keypad; The decoding principle is different depending on the unit. On the TMP47C634, it decodes a matrix between pins 11,
12 and 13 while on the SAA52XX, it only checks to see if the pin is earthed. The TMP47C634 also checks for diodes 6603, 6604 and 6605 via pin
14 on the microcontroller (see options table on diagram).
The SAA52XX reads the options via pins 14 and 52, which will be “1” or “0” depending on the components (2690, 3600, 3650 and 3657).

- TXT: The SAA5290 has an internal teletext decoder. The following functions have been programmed on the software: TXT input/output, show,
freeze, temporary cancellation, clock, subcode, zoom, inde x, flof, page +/-, X/26 and 8/30 pac k et decoding (station identification and start-up page).
Synchronization is received from the HOR FLY and VERT FLY signals, as is the OSD (this means that if the video signal is lost, the TXT does not
become unsynchronized). The teletext information is extracted from the video signal inserted on pins 23 (internal video) and 24 (external video) via
condensers 2635 and 2636.
Pin 27 corresponds to the NIL control signal, which pulse switches transistor 7640 and keeps the picture from interlacing when applied to the
vertical deflector.
All remaining circuitry (oscillator, RGB output, fastblanking, etc.) is shared with the microcontroller.

SYSTEM L/L' BG/L

BG

I

DK

L

L'

LLL

LLH

LLL

LHL

HHL

I

5

Small signal

IC 7015 (TDA836X) is a single-chip video processor with built in IF- detector, luminance and chrominance separator, PAL chroma
decoder, RGB processing , horitzontal&vertical syn. processor, FM sound- decoder,

IF (INTERMEDIATE FRECUENCY) DEMODULATION (ic7015/6A)

IC 7015/6A contains the IF detector. The 38.9 MHz IF signal is a present at the output pin 11 of the tuner (33.4 MHz for a sign al
according to the SECAM L' system).
Bandpass filter; The IF bandpass characteristic is determinated by the bandpass of the SAW (Surface Acoustic Wave) filter 1015.
* For PAL BG sets a SAW filter with 5.5 MHz bandwich is used (33.4 to 38.9 MHz).
* For PAL I sets a SAW filter with a bandwinch of 6.0 MHz is used (33.4 to 39.4 MHz).
* For PAL BGI/SECAM BGLL' sets a SAW filter with 6.0 MHz bandwich is used to enable BGILL' reception.
* For LL' reception BG/L is "high", D6014 conducts and so the 33.4 MHz is tuned to a lower frecuency with C2014 (32.9 to 38.9 MHz).
* For BGIDK reception BG/L is "low", D6014 does no conduct. With C2013 the bandpass filter is tuned at 33.4 MHz (32.4 to 38.9

MHz).

* For PAL BG/SECAM BGDK sets a SAW filter with a bandwich of 6.5 MHz is used without switching possibilities (32.4 to 38.9

MHz).

Demodulation and AGC; After the bandpass filter the IF signal is supplied to the IF-detector IC7015/6A pins 45 and 46. This IC7015
6A is suitable for a both negativ e (BGIDK) and positive (LL') modulation controlled b y the BG/L s witching signal (" high" for LL' positive
modulation, "low" for a BGDIK negative modulation) at pin 1 IC7015/6F (pin 1 IC7015/6F is at DC level input pin for positive/negative
switching of IC7015/6A). This control also determinates whether the AGC circuit controls at the top white le vel (positive modulation) or
at the top sync level (negative modulation).
The high-frecuency AGC voltage is available at pin 47. The take over level of the high-frecuency (delayed) AGC control can be set at
pin 49 by means of R3021. For switching to diferent IF for the SECAM L' system (33.4 MHz) the demodulation reference circuit 5040
at pins 2 and 3 IC7015/6A is switched by switching signal L/L'.
* For BGILDK reception L/L' is "low", D6042 conduct and so coil 5043 is connected in parallel to 5040. The circuit is tuned to 38.9

MHz.

* For reception L/L' is "high", D6042 does nor conduct. The circuit is tuned to 33.4 Mhz by L5040 only.

Note: For sets with LL' reception L5040 is tuned at 33.4 MHz, for sets without LL' reception L5040 is tuned at 38.9 MHz (or 39.5
MHz for PAL I only sets).
Automatic Frecuency Control (AFC) signal at pin 44 is obtained from the reference signal of the IF-detector and the control is
modified internally in IC7015/6A for positive or negative modulation. C2037 smoothes the AFC voltage.

SOURCE SELECT, LUMINANCE AND CHROMINANCE SEPARATION (IC7015/6B)

Sound trap; The baseband CVBS signal of pin 7 IC7015/6A (nominal amplitude of 2Vpp) also contains the 5.5 or 6.0 MHz FM sound
signal (FM intercarrier sound). This sound signal is filtered out with a 5.5 MHz (6.0 MHz PAL I) ceramic filter (1032 and/or 1033).
Source select: The CVBS signal is now fed to pin 13 IC7015/6B to the source selector switch in IC7015/6B. Pin INT/EXT = 0V gives
internal CVBS (pin 13), pin 16 INT/EXT = 8V gives external CVBS (pin 15) (external signal SCART CVBS IN from the CVBS IN cinch
or pin 20 scart-connector).
Luminance and chrominance separation: chrominance signal is filtered out (-20dB) by a luminance notch filter which is internallly
calibrated at the subcarrier frecuency (4.43 or 3.58). The IDENT status signal is coming from pin 14 IC7015/6B. In case of no
horizontal sync (so no signal detected) by the sync processor IC7015/6E, pin 14 IC7015/6B is made "low", TS7651 does not conduct
so pin 16 of the µC is "high". The IDENT signal is internally fed to ensuring stable OSD even without transmiter signal (IC7015/6D can
be switched to different time constants).

CHROMINANCE DECODING (IC7015/6C)

CVBS is extracted from the baseband CVBS signal from the IF-detector via crystals 1032. PAL (and NTSC if applicable) chroma
decoding inside IC7015/6C, SECAM chroma decoding inside IC7250.
Inside IC7015/6C the PAL (or NTSC) chroma signal is fed via amplification and a burst demodulator to the R-Y and B-Y demodulator.
(PAL or NTSC processing is deter mined automatically by the burst demodulator inside IC7015/6C). The 4.43 MHz reference crystal
for chrominance demodulation in IC7015/6Cis in present at pin 35 of IC7015/6C.
Pin 27 shoud be 5V5 (via R3280) to force IC7015 in the PAL/SECAM mode; by then IC7015/6C is in the PAL decoding mode and via
pin 27 feeds throught the chroma signal to the SECAM chroma decoder IC7250 (so IC7015/6C searches for PAL and IC7250
searches for SECAM).

bidirectional communication line between pin 32 of IC7015/6C and pin of IC7250 both IC7015/6C and IC7250 "know" wether

Via a
a PAL or a SECAM signal is detected:

- On AC level there is a

- On DC level there is a SECAM or PAL switching line enabling automatic selection of IC7015/6C and IC7250 to supply R-Y and B­Y to the delay line IC7271.

* If IC7015/6C has detected a PAL signal,

IC7015 / 6C are fed to delay line IC7271.

* If IC7015/6C has detected a PAL signal, Vpin 32 is made 5V. By then the demodulated R-Y and B-Y at output pins 30 and 31 of

IC7015/6C are not fed to the delay line IC7271.

* If IC7250 has detected SECAM

case the sinking current at pin 32 IC7015/6C is typical 150 µA, only by then IC7015/6C "knows" IC7250 has detected SECAM
demodulated R-Y and B-Y are fed to the delay line IC7271 via output pins 9 and 10 of IC7250.

4,43 calibration for calibration of thr PLL and chroma cloche filter of IC7250.

Vpin 32 is made 1V5. By then the demodulated R-Y and B-Y at output pins 30 and 31 od

Vpin 1 IC7250 becomes "low", sinking typical 150 µA from the 5V from pin 32 IC7015/6C. Only in

6

RGB DEMATRIXING (IC7015/6D)

RGB-dematrixing dematrixies the -(R-Y), -(B-Y) and the Y signals; the sandcastle pulse coming from the IC7015/6E synchronises
RGB dematrixing and suppresses the RGB signals during line and frame flyback.
Control by µC for contrast, brightness and saturation (0V5 to 4V5).
RGB-source select switches between internal RGB and external RGB (OSD or SACART) via pin 21 of IC7015/6D (via resp OSD
FAST BLANKING from OSD generator and FAST BLANKING from SACART or µP INT/EXT from µC).

HORIZONTAL SYNCHRONISATION (IC7015/6E) diagram B

Start up of the hor. oscillator via +11A giv es start up current into pin 36 5V8 the hor . oscillator starts running approx. 25 KHz and only
when IC7015 supply pin 10 = 8V the line frecuency changes to 15625 Hz.
Hor, sync., separator separates hor pulses out of CVBS and so synchronises the free-running hor. sawtooth generator. Both the line
and frame frecuencies are internally locked to the chroma oscillator on pin 35 IC7015/6C.
Hor, oscillator sawtooth is converted in square wave voltage with variable duty cycle (pin 37). Hor, flyback pulse at pin 38 compares
phase of flyback pulse with phase of the hor. oscillator ; if phase not correct the duty cycle of hor. oscillator will be adjusted. Time
connstant of the sync. circuit automacallly determinated by IC7015/6E. Pin 38 is both sandcastle output and hor. flyback input.
Selection automacally determinated by the input current (sandcastle a few µA, flyback 100-300 µA determinate by R3371).
Amplitudes of sandcastle pulse; burst 5V3, line blanking is 3V, frame blanking 2V.
At standby (STANDBY "low") TS7580 blocks and TS7581 conducts and so the line is shut down at stand by.

VERTICAL (VERT.) SYNCHRONISATION (IC7015/6E) diagram B

Vert. sync. separator separates frame sync. pulses from CVBS and so synchronises frame oscillator. IC7015/6E compares phase of
flyback pulse with phase of sawtooth at pin 42 (from external RC network); if phase not correct the duty cycle of hor. Pre-amplifier in
IC7015/6E amplifies sawtooth (pin 43 of IC7015/6).
increases (more white), EHT decreases so picture will become too big. BCI and so BCI' decrases for increasing beam current
(diagram C) and the picture will be corrected.

SOUND DETECTION (IC7015/6F) diagram D

There are two audio paths: for the BG, I and DK systems FM modulated intercarrier sound (sound extracted from baseband CVBS
from IF detector), for the LL' systems AM modulated quasi-split sound (sound extracted directly from the tunner).
FM demodulation; For FM modulated sound the sound signal is filtered throught filter 1135 or 1136 from the baseband picture si gnal.
For BGDK or BGILL' sets the switching signal BG/I is used to select the current crystals.
* For I (or DK) reception BG/I is "low", TS7170 does not conduct, D6170 conduct and so crystal 1136 (6.0 MHz for I and 6.5 MHz for

DK) is switched parallel to 1135.

* For BG reception BG/I is "high", TS7170 conduct, D6170 does not conduct and 1136 is not switched in parallel to 1135 (5.5 MHz

only).

* For PAL BG or PAL I only sets only 1135 is used (resp. 5.5 MHz or 6.0 Mhz). FM-mono sound demodulation takes place in

IC7015.6F. No adjustament required for BG or I demodulation as automatic PLL tuning (4.2 to 6.8 MHz).
Sound frecuency characteristic is defined by de-emphasis C2112 at pin 1. Volume control on DC level at pin 5. Selection between
FM sound or AM sound/EXT sound (from input pin 6) by pin 16 IC7015/6B.

AM demodulation; Interferences signals at 30,9 MHz are removed from IF signal coming fron tuner by SAW filter 1137 (double band
pass caracteristic) the required frequency spectrum is fed to the AM demodulation IC7125. The doble characteristic is necessary
because for the L system the sound is at 32,4 MHz and for L´at 39,9 switched by switching signal L/L´and TS 7126 TS7127
* For L´ reception (L/L´ is "high") IF signal is present in pin 2.
* For L reception (L/L´ is "low") IF signal is present in pin 1.
The demodulated signal at pin 6 of IC7125 is supplier to the source selection switch in IC7140 , C2126 and 2127 are AGC related
storage capacitos.
Source selection: INT/EXT is "low " for internal and "high" for external . This signal is made from uP INT/EXT and pin 8 of the scart. If
one of these 2 signals is "high" external is selected. BG/L is "low" for FM sound (BGIDK) and "high" for AM sound (LL').
* Top switch in IC7140 select between AM sound (pin 5) and EXT sound from SCART +AV (pin3) by pin 9 INT/EXT. The output of this

selector (pin 4 IC7150 ) is fed to input pin 6 of FM demodulator IC7015/6F .
Here selection is made between FM sound (pin 5) and EXT sound from SCART+ AV (pin 3) by pin 9 INT/EXT. The output of this
selector (pin 4 IC7150) is fed to input pin 6 of FM demodulator IC7015/6F.

* Middle switch in IC7140 selects between AM (pin 1) and FM sound (pin 2) for SCART AUDIO OUT by pin 10 (BG/L is "high" for AM

pin1, "low" for FM pin2).

* Bottom switch in IC7140 connects +8 to pin 1 IC7015/6F to switch the IF-detector and AGC (both IC7015/6A) to positiv e modulati on

for SECAM LL´(BG/L so pin 11 IC7140 is "high" for AM LL´ positive modulation so pin 13 to +8).

Anti-plop; At switch on the set C2183 is not charged, anode C2183 is "high", TS7183 conducts and so mutes the output amplifier
IC7187. As soon as C2183 is charged anode C2183 is "low", TS7183 stops m uting.
At switch off of the set the +8A drops very fast. As C2183 is still charged, the anode of C2183 becomes approx. -8V DC. By then the
DC volume control signal VOLUME is shorted via zener D6183, so IC7015/6F is muted.

Via BCI' frame correction is realised for high beam currents; If beam current

7

Power Supply

Mains isolated switched mode power supply (SMPS), control IC7514 (TDA4605) gives oscillation, variable frequency, variable duty
cycle, switching FET, no opto coupler, no thrystor switching windings on the secondary side, slow start circuitr y and no standby
mode of the power supply. Via sense windings 4-2 frequency and duty cycle control on the primary side.
Duty cycle and frequency of the power depends on T-on of FET TS7525 which is controlled by IC7514. This IC detects variations
of the +100 (at the secondary side of 5525 at winding 5-7) via sensing windings 4-2 at the primar y side of 5525. The switching
period of TS7525 is divided in three main areas T-on, T-off and T-dead:
During T-on energy is extracted from the mains into the primary winding 8-12 of transformer 5525 with a linear increasing primar y
current (slope depends on voltage across C2505). Via T-on regulation the duty cycle and the frequency of the SMPS and so the
+100 can be controlled.
During T-off energy "inside" transformer is supplied to the load via secondary windings of 5525. Current through secondary side of
the transformer decreases linear with firm slope.
During T-dead no energy is extracted or supplied. During T-dead the L-prim is demagnetised (polarity L-prim and C2524 is switched).

PRIMARY SIDE

Degaussing; R3501 is a dual PTC (2 PTC's in one housing). After switch on set, PTC is cold so low-ohmic and so degaussing
current is very high. After degaussing, PTC is heated so high-ohmic, so in normal operation degaussing current very low.
Mains voltage is filtered by L5500, full wave rectified by diodes 6502-6505 and smoothed by C2505 to VIN (300 V DC for 220V AC
mains).
Start up; Via start up circuitry via R3507 the DC voltage VIN is used to start up IC7514. As soon as the supply voltage Vpin6 12V
the IC7514 starts; the internal oscillator of IC7514 drives TS7525 into conduction at the lowest frequency (during start up C2523
determines the frequency; as C2523 is uncharged at start up this gives a low start). The power supply automatically starts up.
Take over IC7514; During start up a voltage across winding 4-2 is built up. At the moment the voltage across winding 4-2 reaches
approx. +15V, D6521 star ts conducting and takes over the +15 supply voltage at pin 6 IC7514.

CONTROL CIRCUITRY

+100 feedback for frequency and duty cycle control; Sense windings 4-2 has same polarity as winding 5-7. During T-off winding 5­7 and so winding 4-2 are positive. D6515 conducts and so charges C2515; the DC level across C2515 is a reference for the +100.
Via R3518, R3517 and R3508 this DC-voltage is brought to the required level for input pin 1 IC7514; this voltage is used for
frequency and duty cycle control of IC7514.
R3518 is a potentiometer and so +100 can be adjusted.
IC7514 controls +100 by controlling T-on and so the frequency and the duty cycle; IC7514 compares v oltage at pin 1 with an internal
reference voltage.
* In a stable situation the voltage at pin 1 is the same as the internal reference voltage, so frequency and duty cycle remains the

same.

* If +100 increases the voltage at pin 1 increases, and so the frequency and duty cycle and so the +100 will be decreased (new

balance of voltage at pin 1 and the reference voltage and so new lower stable frequency and duty cycle).

* If +100 decreases, the voltage at pin 1 decreases. The frequency and duty cycle and so the +100 will be increased.
The voltage at pin 1 is in a stable situation typical 400 mV.
Undervoltage protection; If Vpin6 supply voltage drops under 7V25, the logic in IC7514 will shut the output at pin 5. The power
supply will stop running.
Overvoltage protection; The power at pin 3 IC7515 is a measure for the mains voltage and so the DC Vin across C2505. As soon
as the voltage Vpin3 6V6, the logic in IC7514 will shut the output at pin 5. The power supply will stop running.
Overload protection; If the secondary load becomes too high, the T-on becomes too long. The internal sawtooth used for oscillation
is measured over C2509 at pin 2 IC7514. If Vpin2 3V (foldback point) the IC will switch into overload mode giving protection (hick­up or burst mode): IC7514 switches TS7525 and so power supply "off" as long as I-prim is too high, starts up again, if I-prim still
too high switches "off" again, etc.

SECONDARY SIDE

±100 for the line output stage ±100A for the tunning (V VARI), +11 for sound output amplifier, +11A for start up of the line circuitry,
±5 for pull up and +5A for µC and EEPROM. No secondary protections are available.

8

Power supply signals

9