ONKYO USA CORPORATION |
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2 0 0 W i l l i a m s D r i v e • R a m s e y N J 0 7 4 4 6 |
0399GENAMP_1 |
2 0 1 - 8 2 5 - 7 9 5 0 F a x 2 0 1 - 8 2 5 - 8 1 5 0 |
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Model: General Subject |
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03/12/99 |
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Classification: SERVICE TIP: |
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BIAS TRANSISTOR ALOCATION or INSTALLATION. |
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On models whose bias transistor may have been mounted far from the heat sink.
Example: Picture shows TX-SV636 or TX-SV535 amplifier output bias transistor Q622, Q624 and at the center is Q616 used for bias.
An amplifier assembly having its bias transistor far from the heat sink should be replaced and rearranged until the transistor body touches the heat sink. Put some heat sink compound between the transistor and heat sink assembly. Such exercise is basic and could provide stable bias at high temperature operation. TXSV636.
Example: TXSV343 may run with higher bias than it should, causing power transformer to open.
1.Idle current begins at no more than 3.5mv at given test points.
2.The bias transistors should be placed up against the heat sink and heat sink compound
should be added as shown.
3. *** R582, and like resistor value may be best if changed from its current value 330ohm to 270ohm.
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