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Denon PMA425R no sound left channel blown
Denon PMA425R no sound left channel blown
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Old 9th April 2019, 05:46 PM   #11
Mooly is offline Mooly  United Kingdom
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Denon PMA425R no sound left channel blown
Whcih resistor did you replace ?

Swap it back for the faulty one and see if the original fault returns.
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Old 10th April 2019, 06:56 AM   #12
ssi is offline ssi  United Kingdom
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R241. The main transistors and drivers were ok but were badly soldered in as it had been repaired before. I did not put everything back on the chasis to test it so some of the grounding wires were not attatched. This is going to be a long term project!
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Old 15th April 2019, 11:21 AM   #13
ssi is offline ssi  United Kingdom
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Hi All


LED's come on for a second on power on then they go out. No relay clicks. Any ideas? Help! Don't want to be beaten by this one! Using DMT througout.


Thanks
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Old 15th April 2019, 01:31 PM   #14
Mooly is offline Mooly  United Kingdom
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Denon PMA425R no sound left channel blown
Work with something you can see as faulty such as the LED behaviour. Look how they are supplied and what conditions are necassary for them to light and then look and see what is missing
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Old 16th April 2019, 09:22 AM   #15
ssi is offline ssi  United Kingdom
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The power transformer gets warm but testing the yellow and white wires / red and black wires there are only mv's not volts. Is it a faulty power supply? I did get a small shock when I was handling it though. Also tested the red and black wires on the board and only mv's.


Fuse is good and also tested it with a replacement.



At a loss at the moment.
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Old 16th April 2019, 11:28 AM   #16
Mooly is offline Mooly  United Kingdom
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Denon PMA425R no sound left channel blown
Any wires from the transformer will be AC volts and not DC...
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Old 17th April 2019, 06:44 AM   #17
ssi is offline ssi  United Kingdom
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Showing my ignorance here but should I be testing the bridge rectifier? Won't have any more time for a bit. This is a long term project.
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Old 17th April 2019, 07:29 AM   #18
Mooly is offline Mooly  United Kingdom
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Denon PMA425R no sound left channel blown
You should measure AC voltage going into the bridge.

If no AC is present then disconnect the transformer secondary and see if the voltage comes up. If not then either the transformer or primary or primary wiring is suspect.

Bridge rectifiers usually fail with at least one of the four diodes going short but that would cause serious overload and should be blowing fuses.
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