Marantz PM-80AF amplifier sometimes turned on output relay don't snap sometimes suction works but the volume increases on the protection of -Service Manual Download|Circuit Download|Download Drawings|schematic download|route map download|free download user manual

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Marantz PM-80AF amplifier sometimes turned on output relay don't snap sometimes suction works but the volume increases on the protection of

Time：2015-06-03 08:19:03 Source：Network Author：Unknown Clicks：1630

2. DC detection (midpoint voltage deviation detection). When the PIN voltage is higher than 0.7 or less than-0.7, protection circuit, the relay releases.
3. DC Test 2, this pin can be used without grounding.
4. grounding.
5. negative power supply terminal, internal integrated circuit substrates. Typical voltage value is -0.75V.
6. the relay drive output.
7. in the discharge circuit. Enough to drive external RC network relay delay time constant.
8. power on the mute control (start up delay connected) Terminal. When the PIN voltage reaches 1.3V, internal relay drive circuit conduction, relay to pull-in.
9. a working power source.
This analysis, 8 pin voltage is abnormal, the circuit is protected, but the midpoint voltage and PIN voltage is measured is not the reason of protecting. Inadvertently using a pointer to the table at this time voltage measuring 1 foot, has found relay to pull-in (pointer table internal resistance is smaller, can lower potential of 1 foot), the PIN is caused by excessive voltage protection, what measure the voltage does not exceed 0.75 v of the said information? Personal analysis there are two possible causes, it is incorrect information, and second, the circuit does not match information.

Further analysis of the reason of a foot protection. 1 foot is overcurrent detection, power head, some parallel port has three parameters sampling for this, all the way to QN03 via RN08---68K resistance of c, b is sampling sources, other RN22 (100K) to plug W05 1 foot to plug W014 penultimate leg, some forming voltage sampling to plus or minus 15 power supply.

Third path 47K RN09 into 7317 9 foot, forming power supply protection sample. Separately one by one, disconnect the three sampling sources, found that when you disconnect the 100K 7317 1 pin voltage drops to-0.65, amplifier to work properly. Road C863 leakage detected capacitance, 103 feet by a capacitor resistor is only 10K, replacement restored the full circuit, everything works fine.

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