Make sure that all the voltages at the secondary of the converter transformer are OK. If not, check SMPS section as described in previous post.
To check the secondary DC voltages, connect a 100W filament type blub acorss the cathode of [D361 - EU2A], and Ground. Disconnect the coil [L 361], by desoldering it out from circuit. Measure all the voltages comes from the secondary of the inverter transformer. The voltage between the cathode and Groundof of (D361) or (voltage acrosss (C 363 - 220Mfd 160V). Make sure that the voltage meausred is 115VDC. A slight variation about +2V or _ve2V can be tolerated.
After making this voltage to OK, reconnect L361 in place, switch ON the set. Measure the voltage acorss C365. Must show around 180VDC. It will be there, if above stated amin voltage 115V is OK.
Locate [R432 - 330 Ohms 1W] resistor on main board, which supplies voltage to horizontal driver transistor. This voltage is taken from [27VDC] from SMPS power supply. If there is no voltage at the collector point of the driver transistor [Q421 - 2SC2383]., chak the continuity of primary winding of line driver transformer [T431], and resistance value of R [R432] there must be a slight voltage difference between two end of the primary winding of [T431], if line drive frequency from [TDA8305] is OK.
If you have a digital multimeter which can count frequenct, the service work will be very easy here.
Check the frequency of the base of Horizontal Output Transistor [Q432 - BU508DF]. It should be around 15625Hz. If not, suspect the horizontal oscillator section. Check the frequency and the base of line drivere transistor. Here also, the frequency must be almost same as stated above.
Desolder out the horizontal output transistor [Q432 BU508DF], and switch ON the set. If frequency measured at the points stated above is OK, make sure that BU 508D is defective. Still there is no oscillation can be measured, suspect [IC 101- TDA 8305A].
But, before replace it, you have to make sure that the line output transofrmer [LOT] is right. There is no way to check the secondary higgh voltage winding to this transofrmer. The only way is to check the heat of the horizontal output transistor [BU508DF]. Just replace the transistor, and switch on the set for a short period of time, say 5 seconds or so. Switch it OFF, unplug it from AC mains wall socket, and feel the heat of the horizontal output tranistor by touch. It can be slight warm. If it overheats, make sure that the LOT is defective, and that was the sets' fault.
To check the secondary DC voltages, connect a 100W filament type blub acorss the cathode of [D361 - EU2A], and Ground. Disconnect the coil [L 361], by desoldering it out from circuit. Measure all the voltages comes from the secondary of the inverter transformer. The voltage between the cathode and Groundof of (D361) or (voltage acrosss (C 363 - 220Mfd 160V). Make sure that the voltage meausred is 115VDC. A slight variation about +2V or _ve2V can be tolerated.
After making this voltage to OK, reconnect L361 in place, switch ON the set. Measure the voltage acorss C365. Must show around 180VDC. It will be there, if above stated amin voltage 115V is OK.
Locate [R432 - 330 Ohms 1W] resistor on main board, which supplies voltage to horizontal driver transistor. This voltage is taken from [27VDC] from SMPS power supply. If there is no voltage at the collector point of the driver transistor [Q421 - 2SC2383]., chak the continuity of primary winding of line driver transformer [T431], and resistance value of R [R432] there must be a slight voltage difference between two end of the primary winding of [T431], if line drive frequency from [TDA8305] is OK.
If you have a digital multimeter which can count frequenct, the service work will be very easy here.
Check the frequency of the base of Horizontal Output Transistor [Q432 - BU508DF]. It should be around 15625Hz. If not, suspect the horizontal oscillator section. Check the frequency and the base of line drivere transistor. Here also, the frequency must be almost same as stated above.
Desolder out the horizontal output transistor [Q432 BU508DF], and switch ON the set. If frequency measured at the points stated above is OK, make sure that BU 508D is defective. Still there is no oscillation can be measured, suspect [IC 101- TDA 8305A].
But, before replace it, you have to make sure that the line output transofrmer [LOT] is right. There is no way to check the secondary higgh voltage winding to this transofrmer. The only way is to check the heat of the horizontal output transistor [BU508DF]. Just replace the transistor, and switch on the set for a short period of time, say 5 seconds or so. Switch it OFF, unplug it from AC mains wall socket, and feel the heat of the horizontal output tranistor by touch. It can be slight warm. If it overheats, make sure that the LOT is defective, and that was the sets' fault.
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