Fig.3 Schematic diagram of the Funai 2000 MK7 TV power supply
Posted: Mon Feb 17, 2025 3:41 am
In the best case, due to the increase in current through the Q601 transistor of the BUT11F type, this will lead to the burnout of the R605 resistor, and in most cases - to the failure of a number of electronic components in the TV circuit and, first of all, the aforementioned BUT11F transistor.
When repairing a Philips 2021 TV, in addition to replacing the failed parts, to avoid a recurrence of the malfunction, you should replace the electrolytic capacitor in position C610 with a 100 μF capacitor rated for 63 V.For more reliable operation of the TV, it is recommended to install the same capacitor in position C612.
The failure of the once very popular Funai 2000 MK7 TVs also occurs due to a sharp increase in the output voltage of the power supply (see the figure below).
In these TVs, in case of a sharp increase in the line scan belgium telegram data supply voltage - 115 volts, a protective diode of the R2M type (position number on the diagram D245) with a breakdown voltage of 135 to 150 volts is used. When this voltage is exceeded, the protective diode R2M breaks down and shorts the supply circuit of the line scan output stage to the case, which, naturally, leads to a breakdown of generation and the cessation of the TV power supply.
Checking other parts of the circuit often does not reveal any faulty ones, which leads to a false conclusion about replacing only the mentioned protective avalanche diode R2M or, if there is no working one, about removing it, which is unacceptable, since it leads to the failure of many components of the TV: the horizontal scanning output stage, the control processor, and the vertical scanning microcircuit.
Let's consider another common defect of the power supply of these TVs, in which stabilization is carried out by means of feedback through the optoelectronic pair Q505 (Fig. 3). Information from the 115 V voltage source is fed to it through the measuring transistor Q235, and the optocoupler itself controls the regulating transistor Q504, which ensures stabilization of the output voltages.
When repairing a Philips 2021 TV, in addition to replacing the failed parts, to avoid a recurrence of the malfunction, you should replace the electrolytic capacitor in position C610 with a 100 μF capacitor rated for 63 V.For more reliable operation of the TV, it is recommended to install the same capacitor in position C612.
The failure of the once very popular Funai 2000 MK7 TVs also occurs due to a sharp increase in the output voltage of the power supply (see the figure below).
In these TVs, in case of a sharp increase in the line scan belgium telegram data supply voltage - 115 volts, a protective diode of the R2M type (position number on the diagram D245) with a breakdown voltage of 135 to 150 volts is used. When this voltage is exceeded, the protective diode R2M breaks down and shorts the supply circuit of the line scan output stage to the case, which, naturally, leads to a breakdown of generation and the cessation of the TV power supply.
Checking other parts of the circuit often does not reveal any faulty ones, which leads to a false conclusion about replacing only the mentioned protective avalanche diode R2M or, if there is no working one, about removing it, which is unacceptable, since it leads to the failure of many components of the TV: the horizontal scanning output stage, the control processor, and the vertical scanning microcircuit.
Let's consider another common defect of the power supply of these TVs, in which stabilization is carried out by means of feedback through the optoelectronic pair Q505 (Fig. 3). Information from the 115 V voltage source is fed to it through the measuring transistor Q235, and the optocoupler itself controls the regulating transistor Q504, which ensures stabilization of the output voltages.