TV (Chinese) AK ELECTRONIC MODEL AK21FL does not turn on, B + (72V)
IRT TCR1427.pdf [334.50kb]
For this chassis and TV model the voltage of + BH is: 110V.
Regards.
First, I would disconnect the horizontal output transistor, put the + BH voltage input
a resistor of approximately 400 Ohm -25W between that point and GND. Check the voltage at that point,
If it is low, check resistor R966 = 220 KOhm and the value of resistor R972 = 4.7 KOhm. To continue without
Finding the problem controls these components: VD956 = 3.9V; VD910 = 16V-1 / 2W; VD912 = 6.2V- 1 / 2W,
C947 = 33uF x160V; C932 = 330 uF x 16V.
Thank you friend, I already have the operational source, the voltages with the test load is in B + 102 V, at the 12V output I have 11.18 V at the 25V output there are 24.74V and at the 26V output it is a bit high at 32.72 V, the reference voltages are those indicated by the DIAGRAM. The measurements are with the Vcc and ground of the audio amplifier and vertical interconnect disconnected. With which I can rule out failure at source level
Thanks friend for your opinion, thanks to your question I realized I was only measuring only the source in stamby, I have 72 V in stamby and 102 in on, The horizontal transistor between collector and emitter, in one sense the diode measures me and in opposite polarity measures me leakage, I will check the rest of the source voltages
,
And how much it measures in the collector of the DRIVER HORIZONTAL transistor. In STBY and ON?
Friend the horizontal predriver is in good condition, there is an input signal at its base and in the collector there is approximately 200 Vpp signal, this seen with the oscilloscope, at the output of the transformer that feeds the base of the horizontal transistor there is also signal 120 Vpp all this only on, in stamby there is no signal, so the jungle is providing the horizontal oscillation frequency, all these tests are with dummy load, bone without Horizontal transistor
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