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audio amp replacement

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danshot

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I have a Pioneer car stereo. No sound out of the speakers. After google searches on my problem, I leaned toward the possibley it was the audio amp. So, I took the thing apart and got the amp part number. Ordered the part. The only difference in the amps were the markings on the amp. Yeh part numbers were the same. PAL007A. The old one had a small 0.4 inprinted on the lower right conrner. The new amp had a 0.8 in the same location. I went ahead with the replacement. I hooked the radio up with my 12 volt converter and a speaker. The speakers worked , which befroe did no. ?The only thing now is my 12v converter circuit breaker pops when I turn up the volume. I can feel the amp get hot on volume increase. Wondering if someone might know what the 0.4 or 0.8 means and if it's significant. The MOSFET part number is PAL007a. Any help is appreciated.
 
Thanks. Can you elaborate a little on checking for DC at the speaker with no input. Does that mean with stero off, or just no volume?
 
The datasheet for the TDA7560 amplifier IC shows that its output is 45 Whats per channel when the power supply voltage is much too high at 14.4V, its load is 4 ohms and its volume control is turned up way too high so the amplifier is clipping like mad with horrible distortion. Its output is a saturated square-wave.

Its output when its supply voltage is a reasonable 13.2V into a 4 ohm load is 19 Watts per channel when its output is clipping less than before with 1% distortion. When its output is 10kHz and is barely clipping its output power is only 15 Watts.

The IC is able to drive a load as low as only 2 ohms with more output power.

Bridged audio amplifiers in cars have half the battery voltage on both wires of each speaker.
 
No volume is fine. Put a DC voltmeter on the speaker terminals. Idealy, a few mV for a VERY good amp. In the range pf 75 mV is permissable. if the amp is thermally stable, the DC offset should change too much when the AMP heats up. 1V and climbing isn't OK.

You did use heat sink grease on the IC? There are various mounting systems. Thermal pads (usually grey) don't require heat sink grease.
 
Put a DC voltmeter on the speaker terminals. Idealy, a few mV for a VERY good amp. In the range pf 75 mV is permissable.
No.
The amplifier does not have a dual-polarity supply, it has only a positive supply. So its outputs are at half the supply voltage.
The voltage between the speaker terminals should be no more than 60mV.
 
Semantics. That's what i meant to say. What's a few millivolts (15) amoung friends. The use of between or across the speaker terminals is much better.
 
Well, if there is no sound, not even a hiss from the speaker then maybe the output transistors are toast.
 
I took the reading across the speaker terminals. I got approx 29 mV, Changing very little with volume increase. I was not getting the exact same reading with different speaker positions. Some were a low as 10-14 mV. Funny thing is, on two pair of speaker wires i was getting a negative mV reading. I triple checked the polarity on the wires. Of course if I switched them it changed to positive. The amp did not get to hot today. So, I'm going to install it in the car soon. So hopefully it'll work. I did use clips (alligator) while soldering. The amp does have a heat sink on it (gray metal plate). What is heat sink grease? Is that flux?
 
Heat sink grease increases thermal conductivity from the part to the heatsink.
 
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