Hey guys i have a US audio m5150 mono block amplifier. It's the same board in the lanzar opti 7000k
The Amp is working however when you power up the Amp and attach a load to the output (to wake up the output) this resistor gets awful hot!! Also if u play a small load on the amplifier the output transformers get extreamly hot. Now this resistor is reading as shorted.
The amplifier was repaired from a constant in protect mode and chip ir2113 was replaced. Now amp works however gets extreamly hot for no reason.
I'll attach a few pics of what parts I'm talking about.
I plan on replacing the resistor but as I don't have a schematic I can't really test other components.
Red circle is the replaced driver chip ir2113
Green circle is of the resistor that gets awful hot as soon as the output is activated.
I might add no other resistors near any of the other drivers or transformers gets hot. It's only the one resistor but all 4 transformers get extreamly hot
(just having trouble uploading photos)
The Amp is working however when you power up the Amp and attach a load to the output (to wake up the output) this resistor gets awful hot!! Also if u play a small load on the amplifier the output transformers get extreamly hot. Now this resistor is reading as shorted.
The amplifier was repaired from a constant in protect mode and chip ir2113 was replaced. Now amp works however gets extreamly hot for no reason.
I'll attach a few pics of what parts I'm talking about.
I plan on replacing the resistor but as I don't have a schematic I can't really test other components.
Red circle is the replaced driver chip ir2113
Green circle is of the resistor that gets awful hot as soon as the output is activated.
I might add no other resistors near any of the other drivers or transformers gets hot. It's only the one resistor but all 4 transformers get extreamly hot
(just having trouble uploading photos)
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HI. That black stuff is just glue. But how would I check to see if it's shorted?
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That resistor may be a resistor that's across the rail to discharge the rail caps. If so, it will get hot as soon as the power supply switches on.
The inductors in many amps are made to order by bean counters and therefore the cheapest possible. Fewer turns of copper and cheaper cores will make the inductors run hot. It's possible but unlikely to have 4 defective inductors.
The inductors in many amps are made to order by bean counters and therefore the cheapest possible. Fewer turns of copper and cheaper cores will make the inductors run hot. It's possible but unlikely to have 4 defective inductors.
HI perry. I have 2 of these amplifiers and if I check the other one that resistor in circuit reads ohms. Also on the other side of the board of the faulty amp that resistor also reads. It's only this 1 resistor that is shorted in circuit and normal out of circuit.
The Amp was working perfectly fine before the driver chip let go.
No other resistors around the inductors gets hot. Only this 1.
But all the inductors along with this resistor get HOT and I mean burn you're hand hot. But amp works fine?
I can't trace very far from that resistor as the trace goes under the inductor and a bunch of glue.
I may add all this heat comes from simply activating the output by putting a 4ohm load on it. On a 20a power supply. Not playing any music
This board comes apart into 2 pieces. So at the moment just the output side is out.
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Yes they all check out fine. As I said the Amp now works fine and puts out a clean signal on the output. Does not draw too much current it just is running extremely hot. And u can smell burning as a result.
What caused all this mess was a slip of a multimeter probe where the power supply joins to the output. You can kind of see where they slipped pins are a bit distorted.
I found why it was cycling between power and protect. Was ir2113. Replaced that. But now having heat problems.
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It got extremely hot. And also one 22ohm resistor I must have accidentally broke when I was taking the heat sink clips off. It could have been broken previously I'm not sure.
Edit. Sorry I don't think I need to replace the 15k resistor that's getting really hot it checked out fine out of circuit.
But I will need to replace the broken 22ohm one of the legs were snapped off it was mounted vertical on the board
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I get a direct short between the legs on the left(in photo) on the mosfets circled too one side of the resistor getting hot
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It's not only that resistor that gets hot. All the output inductors get burning hot. And the resistor on the other side stays nice and cool?
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