Audio Power Amplifier repair

Thread Starter

satcom

Joined Apr 1, 2015
62
I am considering a purchase of compact audio system for room. The CD receiver RCD-M40 I wanted was discontinued, but I have an offer for a used one (visually good condition, with all accessories), it's sold as non-working or for parts. When power on, LED is flashing red. According to Troubleshooting tips from Owner’s manual, this symptom can be caused due to amplifier circuit in the unit has malfunctioned. I have a Service Manual for this model, with schematic diagram and Part lists. Unfortunately, assembled PCB's for device is not supplied, include this power Amplifier PCB Assy, so repair is at the individual components level. Can anyone advice about proper steps how to find and replace the faulty components in this PCB?
PowAmp-A.png PowAmp-B.png
 

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danadak

Joined Mar 10, 2018
3,577
Look for -

1) Leakage around electrolytic cap. They are the polarized ones.
2) Bulging top of electrolytic cap -



3) Heat discoloration PCB close to a component. Component failure.
4) Resistors, especially larger ones, discolored, burnt looking.

Any of these failures can takle out other components, so check those.

Post pics of actual PCB. Closeups.


Regards, Dana.
 

MrSoftware

Joined Oct 29, 2013
1,563
The first step is figuring out what is wrong with it. As mentioned above, capacitors are a common failure point, and any other visual hints you can find could also be helpful. That's the easiest place to start.
 

Thread Starter

satcom

Joined Apr 1, 2015
62
Look for -

1) Leakage around electrolytic cap. They are the polarized ones.
2) Bulging top of electrolytic cap -
3) Heat discoloration PCB close to a component. Component failure.
4) Resistors, especially larger ones, discolored, burnt looking.

Any of these failures can takle out other components, so check those.

Post pics of actual PCB. Closeups.


Regards, Dana.
Thanks for your input. I haven't bought this audio center yet, so while it's all preliminary. For now I want to understand how reliable is a PCB repair when manually soldering discrete components and chips. The manufacture date is 2015-03. Disassembling this mini center is a rather difficult procedure, can be a real pain due to its small size and tight montage, plenty of screws and small details, wires, FFC cables for board-to-board connection .
 
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Ylli

Joined Nov 13, 2015
776
Is it flashing every quarter second or every half second? Two different failure codes.

This unit uses an integrated power amp, an STK-433-60N. We can walk you through a lot of troubleshooting steps to confirm what the issue is, but I'd give it 50/50 that the integrated module is blown. The part does seem to be available from bdent.com or from ebay, cost about $10. (bdent is generally a reliable source, ebay sells a lot of counterfeit parts) But it would take some good soldering skills to replace it.

I'd suggest you find a different unit.
 

Thread Starter

satcom

Joined Apr 1, 2015
62
I haven't seen it in place, but I suppose it flashes at 1/4 sec intervals.
If it was 1/2 sec this would mean that was a recoverable fault, protection circuit activated due to a rise in internal temperature, or core wires of two speakers are touching each other. I think it's not the case.
 

Thread Starter

satcom

Joined Apr 1, 2015
62
Who is manufacturer of capacitors with these part numbers? Is it special series for audio applications made for Denon? Can't find anything.

CAP, ELECT(25V/470uF) CCEA1EH471E
CAP, ELECT(50V/47uF) CCEA1HH470T
CAP, METAL-FILM(100V/0.047uF) CCME2A473JXT
 
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