Denon PMA-1560 defective circuit - diyAudio
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Old 19th September 2015, 01:45 PM   #1
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Default Denon PMA-1560 defective circuit

Hello everyone! I got this from a friend of mine, It doesn't works. I opened it I founded there were three burned resistors. So, I replaced them, but when I turned on the amp, they broke again. I found the schematics on the web and I started studying it and testing some components.
I uploaded the scheme with marked the problem that I've. Click the image to open in full size.
In red R531, R537, R539 the three resistors that I found burned. I tested the outputs from the main power unit (circled in green), they should be +/- 66.4 V, mine are +/- 72.3.
Now... I don't know where the problem is. Probably the toroidal trans? or the four capacitors? I'm not so expert.
Can somebody help me?
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Old 19th September 2015, 02:41 PM   #2
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Nothing wrong with the toroid. Repair the amplifier; check or leaky transistors.
Check the driver transistors that are connected to the bvurnt up safety resistors. When you have found the fault, replace the safety resistors with exactly the same type and value, for safety.
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Last edited by JonSnell Electronic; 19th September 2015 at 02:44 PM.
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Old 19th September 2015, 02:45 PM   #3
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I replaced TR511, TR509, TR513 and TR517, nothing changed. Could be something between the three resistors? And I forgot to say that even on the other amplifier I found burned the same exact resistors.

Last edited by Antenore; 19th September 2015 at 02:50 PM.
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Old 23rd August 2016, 08:19 AM   #4
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you can check if inside on the board the resistore from R549 to R556 are 47 ohm or 470 ohm... There is a mistake
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Old 23rd August 2016, 08:59 AM   #5
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This is an expert level project. Not recommended for a beginner, it will not end well.
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Old 23rd August 2016, 09:12 AM   #6
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Please be aware that NB on the resistor description means Flame Retardant or Non Burnable. They will not catch fire when something goes wrong. Always replace like for like for your own safety!
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Old 23rd August 2016, 10:25 AM   #7
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On diagram there is 47 ohm But in component list 470 ohm...
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Old 4th October 2016, 10:39 PM   #8
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Ok, there is probably an error, but I'm not even touching the R549 or other resistors. My problem is that R531, R537, R539 keeps burning.
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