Radio and television DS7188AV power amplifier a protective relay on the action, the characters on the screen non-stop flashing |
| Time£º2015-05-25 08:44:56 Source£ºNetwork Author£ºUnknown Clicks£º1344 |
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Vt6service manual download site
Replace push, excitation and bias transistor:Q120, Q130, Q124, Q125, Q132, Q133 and Q136. The base voltage of the power tube is B: the 0.4V of 10V is decreased by O.9V, the B voltage of Q0 is decreased by 0.2V to Q1. The replacement of the transistor is invalid, the estimate is to promote the starting moment of the self excited oscillation.Vt6service manual download site
The power amplifier excitation tube C - B between the not designed dissipation capacitance. Trial 33pf ceramic capacitor is connected to the excitation tube q120, between Q130 B-C, used to suppress the oscillation circuit, phase compensation, the elimination of high frequency circuit of the self-excited oscillation.Vt6service manual download site
The B voltage of Q1 is B with the 0.8V.Q0 electrode voltage of 1.1V. They measured the load resistance of R129 is 270, R128zuzhi value is: 360. Estimated for the repair personnel to adjust the power tube voltage of base changes in the original design of Zuzhi resistance. The R128 and R129 to the original design of 100. The B of the Q1 is -0.7V, the B electrode voltage of Q0 is +0.7V. See the problem from the excitation has been resolved. High power tube base voltage symmetry, but high, should be in the 0.5V, so that the high power tube to work in a and a B class. The bias tube Q136 base bias resistor R132 is transferred from 1.8K to 2.7K, and R134 is transferred from 1.47k to 4.7K..Vt6service manual download site
The B voltage of Q1 is B with the -0.5V:Q0 electrode voltage of +0.5V. High power transistor base voltage is normal, the power tube installed, the normal boot, measuring the midpoint voltage is 5.6mV. Then one morning speaker highpowervalve normal temperature rise.Vt6service manual download site
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