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danandnat

Marantz 1180dc phono one channel is out

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My Marantz 1180dc stereo . Works very well. Both Channels work on all the other inputs except Phono 1 and Phono 2 inputs are missing the left channel.

I am willing to open this amplifier up and try to work out were the problem maybe.

 

I have reasonable multimeter skills and I have done some basic electronic repairs.

 

Can anyone help

 

Thanks in advance

 

Dan

 

 

 

 

 

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676eba10f7c65cca52fcdf44e4099a90.png

ca3db2333094b168d946eaeb2c99cb10.png

I downloaded the schematic from hifiengine.com

Next i will open it up and have a look .



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So i opened my Marantz 1180dc stereo console today. All look ok . Could find any damaged components or bad solder joints.
So detoxed the selector controls . I have worked the controls back and forth.
I turn it on again once the deoxit has dissipated .



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A common fault with the 1180DC is the upper printed circuit board. Dust accumulates on the board and, due to the relatively high Voltages present, can lead to 'tracking' problems. Hairline cracks and corrosion are also very common issues with this part of the 1180DC. Clean the upper PCB (isopropanol) and examine carefully for cracks. Additionally, due to the tracking problems, you may also find several failed transistors and resistors in the phono stage. You'll need a service manual and the usual skills to fix the problem.

 

BTW: You don't have to wait for Deoxit to evaporate. It you do, you'll be waiting a very, VERY long time. 

Edited by Zaphod Beeblebrox

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ophool   

No doubt it has already been checked and eliminated, but I would think of checking the turntable interconnect first if both phono inputs have the same issue.  Just swap the channels at the inputs and see if the problem changes sides.

Failing that, Zaph knows this kit.

Edited by ophool

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No doubt it has already been checked and eliminated, but I would think of checking the turntable interconnect first if both phono inputs have the same issue.  Just swap the channels at the inputs and see if the problem changes sides.
Failing that, Zaph knows this kit.

Yep done that already.


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Houston we have a problem !

I just turned it on and now the overload led is in and these resistors are smokinh hot!
f9456a57032818efec44c676016b67ce.jpg


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Wimbo   

I was gonna say, Send it to Trevor. He knows a lot about old Marantz kit. But your in Junee. Talk to Trevor on here as to what to do after his first instructions.Would be great to follow.:)

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I suspect i caused some short circuits due to the deoxit.

I can see visible resistor burn. Some possibly some short transistors?


I may need some professional help.

As i am making things worse.


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12 hours ago, danandnat said:

Houston we have a problem !

I just turned it on and now the overload led is in and these resistors are smokinh hot!
f9456a57032818efec44c676016b67ce.jpg


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I doubt that those beige coloured resistors are original. They should be flameproof types. In any case, the resistors are a symptom of the real problem, which likely be one or more transistors that have failed. Then you need to determine why the transistors have failed. Look for corrosion and tracking on the PCB.

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I doubt that those beige coloured resistors are original. They should be flameproof types. In any case, the resistors are a symptom of the real problem, which likely be one or more transistors that have failed. Then you need to determine why the transistors have failed. Look for corrosion and tracking on the PCB.


Thankyou for your advice.

I feel i am out of my depth here. Would anyone here do repairs for me?

I will go other the pcb more closely.

There has been some previous repair work on the pcb.



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